151
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Nawrath C. Unraveling the complex network of cuticular structure and function. CURRENT OPINION IN PLANT BIOLOGY 2006; 9:281-7. [PMID: 16580871 DOI: 10.1016/j.pbi.2006.03.001] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Accepted: 03/20/2006] [Indexed: 05/08/2023]
Abstract
A hydrophobic cuticle is deposited at the outermost extracellular matrix of the epidermis in primary tissues of terrestrial plants. Besides forming a protective shield against the environment, the cuticle is potentially involved in several developmental processes during plant growth. A high degree of variation in cuticle composition and structure exists between different plant species and tissues. Lots of progress has been made recently in understanding the different steps of biosynthesis, transport, and deposition of cuticular components. However, the molecular mechanisms that underlie cuticular function remain largely elusive.
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Affiliation(s)
- Christiane Nawrath
- University of Lausanne, Department of Plant Molecular Biology, Biophore Building, UNIL-Sorge, CH-1015 Lausanne, Switzerland
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152
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Kurdyukov S, Faust A, Nawrath C, Bär S, Voisin D, Efremova N, Franke R, Schreiber L, Saedler H, Métraux JP, Yephremov A. The epidermis-specific extracellular BODYGUARD controls cuticle development and morphogenesis in Arabidopsis. THE PLANT CELL 2006; 18:321-39. [PMID: 16415209 PMCID: PMC1356542 DOI: 10.1105/tpc.105.036079] [Citation(s) in RCA: 222] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The outermost epidermal cell wall is specialized to withstand pathogens and natural stresses, and lipid-based cuticular polymers are the major barrier against incursions. The Arabidopsis thaliana mutant bodyguard (bdg), which exhibits defects characteristic of the loss of cuticle structure not attributable to a lack of typical cutin monomers, unexpectedly accumulates significantly more cell wall-bound lipids and epicuticular waxes than wild-type plants. Pleiotropic effects of the bdg mutation on growth, viability, and cell differentiation are also observed. BDG encodes a member of the alpha/beta-hydrolase fold protein superfamily and is expressed exclusively in epidermal cells. Using Strep-tag epitope-tagged BDG for mutant complementation and immunolocalization, we show that BDG is a polarly localized protein that accumulates in the outermost cell wall in the epidermis. With regard to the appearance and structure of the cuticle, the phenotype conferred by bdg is reminiscent of that of transgenic Arabidopsis plants that express an extracellular fungal cutinase, suggesting that bdg may be incapable of completing the polymerization of carboxylic esters in the cuticular layer of the cell wall or the cuticle proper. We propose that BDG codes for an extracellular synthase responsible for the formation of cuticle. The alternative hypothesis proposes that BDG controls the proliferation/differentiation status of the epidermis via an unknown mechanism.
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153
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Lee JJ, Hassan OSS, Gao W, Wei NE, Kohel RJ, Chen XY, Payton P, Sze SH, Stelly DM, Chen ZJ. Developmental and gene expression analyses of a cotton naked seed mutant. PLANTA 2006; 223:418-32. [PMID: 16254724 DOI: 10.1007/s00425-005-0098-7] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2005] [Accepted: 07/25/2005] [Indexed: 05/05/2023]
Abstract
Cotton fiber development is a fundamental biological phenomenon, yet the molecular basis of fiber cell initiation is poorly understood. We examined molecular and cellular events of fiber cell development in the naked seed mutant (N1N1) and its isogenic line of cotton (Gossypium hirsutum L. cv. Texas Marker-1, TM-1). The dominant mutation not only delayed the process of fiber cell formation and elongation but also reduced the total number of fiber cells, resulting in sparsely distributed short fibers. Gene expression changes in TM-1 and N1N1 mutant lines among four tissues were analyzed using spotted cotton oligo-gene microarrays. Using the Arabidopsis genes, we selected and designed approximately 1,334 70-mer oligos from a subset of cotton fiber ESTs. Statistical analysis of the microarray data indicates that the number of significantly differentially expressed genes was 856 in the leaves compared to the ovules (3 days post-anthesis, DPA), 632 in the petals relative to the ovules (3 DPA), and 91 in the ovules at 0 DPA compared to 3 DPA, all in TM-1. Moreover, 117 and 30 genes were expressed significantly different in the ovules at three and 0 DPA, respectively, between TM-1 and N1N1. Quantitative RT-PCR analysis of 23 fiber-associated genes in seven tissues including ovules, fiber-bearing ovules, fibers, and non-fiber tissues in TM-1 and N1N1 indicates a mode of temporal regulation of the genes involved in transcriptional and translational regulation, signal transduction, and cell differentiation during early stages of fiber development. Suppression of the fiber-associated genes in the mutant may suggest that the N1N1 mutation disrupts temporal regulation of gene expression, leading to a defective process of fiber cell elongation and development.
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Affiliation(s)
- Jinsuk J Lee
- Department of Soil and Crop Sciences and Intercollegiate Program in Genetics, Texas A&M University, MS 2474/Molecular Genetics, College Station, TX 77843, USA
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154
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Abstract
Plants are subject to a wide range of abiotic stresses, and their cuticular wax layer provides a protective barrier, which consists predominantly of long-chain hydrocarbon compounds, including alkanes, primary alcohols, aldehydes, secondary alcohols, ketones, esters and other derived compounds. This article discusses current knowledge relating to the effects of stress on cuticular waxes and the ways in which the wax provides protection against the deleterious effects of light, temperature, osmotic stress, physical damage, altitude and pollution. Topics covered here include biosynthesis, morphology, composition and function of cuticular waxes in relation to the effects of stress, and some recent findings concerning the effects of stress on regulation of wax biosynthesis are described.
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Affiliation(s)
- Tom Shepherd
- Quality Health & Nutrition, Scottish Crop Research Institute, Mylnefield, Invergowrie, Dundee DD2 5DA.
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155
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Suh MC, Samuels AL, Jetter R, Kunst L, Pollard M, Ohlrogge J, Beisson F. Cuticular lipid composition, surface structure, and gene expression in Arabidopsis stem epidermis. PLANT PHYSIOLOGY 2005; 139:1649-65. [PMID: 16299169 PMCID: PMC1310549 DOI: 10.1104/pp.105.070805] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 09/22/2005] [Accepted: 09/23/2005] [Indexed: 05/05/2023]
Abstract
All vascular plants are protected from the environment by a cuticle, a lipophilic layer synthesized by epidermal cells and composed of a cutin polymer matrix and waxes. The mechanism by which epidermal cells accumulate and assemble cuticle components in rapidly expanding organs is largely unknown. We have begun to address this question by analyzing the lipid compositional variance, the surface micromorphology, and the transcriptome of epidermal cells in elongating Arabidopsis (Arabidopsis thaliana) stems. The rate of cell elongation is maximal near the apical meristem and decreases steeply toward the middle of the stem, where it is 10 times slower. During and after this elongation, the cuticular wax load and composition remain remarkably constant (32 microg/cm2), indicating that the biosynthetic flux into waxes is closely matched to surface area expansion. By contrast, the load of polyester monomers per unit surface area decreases more than 2-fold from the upper (8 microg/cm2) to the lower (3 microg/cm2) portion of the stem, although the compositional variance is minor. To aid identification of proteins involved in the biosynthesis of waxes and cutin, we have isolated epidermal peels from Arabidopsis stems and determined transcript profiles in both rapidly expanding and nonexpanding cells. This transcriptome analysis was validated by the correct classification of known epidermis-specific genes. The 15% transcripts preferentially expressed in the epidermis were enriched in genes encoding proteins predicted to be membrane associated and involved in lipid metabolism. An analysis of the lipid-related subset is presented.
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Affiliation(s)
- Mi Chung Suh
- Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA
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156
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Franke R, Briesen I, Wojciechowski T, Faust A, Yephremov A, Nawrath C, Schreiber L. Apoplastic polyesters in Arabidopsis surface tissues--a typical suberin and a particular cutin. PHYTOCHEMISTRY 2005; 66:2643-58. [PMID: 16289150 DOI: 10.1016/j.phytochem.2005.09.027] [Citation(s) in RCA: 245] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 09/20/2005] [Accepted: 09/21/2005] [Indexed: 05/02/2023]
Abstract
Cutinized and suberized cell walls form physiological important plant-environment interfaces as they act as barriers limiting water and nutrient loss and protect from radiation and invasion by pathogens. Due to the lack of protocols for the isolation and analysis of cutin and suberin in Arabidopsis, the model plant for molecular biology, mutants and transgenic plants with a defined altered cutin or suberin composition are unavailable, causing that structure and function of these apoplastic barriers are still poorly understood. Transmission electron microscopy (TEM) revealed that Arabidopsis leaf cuticle thickness ranges from only 22 nm in leaf blades to 45 nm on petioles, causing the difficulty in cuticular membrane isolation. We report the use of polysaccharide hydrolases to isolate Arabidopsis cuticular membranes, suitable for depolymerization and subsequent compositional analysis. Although cutin characteristic omega-hydroxy acids (7%) and mid-chain hydroxylated fatty acids (8%) were detected, the discovery of alpha,omega-diacids (40%) and 2-hydroxy acids (14%) as major depolymerization products reveals a so far novel monomer composition in Arabidopsis cutin, but with chemical analogy to root suberin. Histochemical and TEM analysis revealed that suberin depositions were localized to the cell walls in the endodermis of primary roots and the periderm of mature roots of Arabidopsis. Enzyme digested and solvent extracted root cell walls when subjected to suberin depolymerization conditions released omega-hydroxy acids (43%) and alpha,omega-diacids (24%) as major components together with carboxylic acids (9%), alcohols (6%) and 2-hydroxyacids (0.1%). This similarity to suberin of other species indicates that Arabidopsis roots can serve as a model for suberized tissue in general.
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Affiliation(s)
- Rochus Franke
- Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany.
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157
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Chen X, Goodwin SM, Liu X, Chen X, Bressan RA, Jenks MA. Mutation of the RESURRECTION1 locus of Arabidopsis reveals an association of cuticular wax with embryo development. PLANT PHYSIOLOGY 2005; 139:909-19. [PMID: 16183838 PMCID: PMC1256005 DOI: 10.1104/pp.105.066753] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 08/11/2005] [Accepted: 08/14/2005] [Indexed: 05/04/2023]
Abstract
Insertional mutagenesis of Arabidopsis (Arabidopsis thaliana) was used to identify a novel recessive mutant, designated resurrection1 (rst1), which possesses a dramatic alteration in its cuticular waxes and produces shrunken nonviable seeds due to arrested embryo development. The RST1 gene sequence associated with these phenotypes was verified by three independent, allelic, insertion mutants, designated rst1-1, rst1-2, and rst1-3, with inserts in the first exon, 12th intron, and fourth exon, respectively. These three rst1 allelic mutants have nearly identical alterations in their wax profiles and embryo development. Compared to wild type, the wax on rst1 inflorescence stems is reduced nearly 60% in total amount, has a proportional reduction in aldehydes and aldehyde metabolites, and has a proportional increase in acids, primary alcohols, and esters. Compared to wild type, the C(29) alkanes on rst1 are nearly 6-fold lower, and the C(30) primary alcohols are 4-fold higher. These results indicate that rst1 causes shunting of most wax precursors away from alkane synthesis and into the primary-alcohol-producing branch of the pathway. In contrast to stems, the wax on rst1 mutant leaves increased roughly 43% in amount relative to the wild type, with the major increase occurring in the C(31) and C(33) alkanes. Unique among known wax mutants, approximately 70% of rst1 seeds are shrunken and nonviable, with these being randomly distributed within both inflorescence and silique. Viable seeds of rst1 are slightly larger than those of wild type, and although the viable rst1 seeds contain more total triacylglycerol-derived fatty acids, the proportions of these fatty acids are not significantly different from wild type. Shrunken seeds contain 34% of the fatty acids of wild-type seeds, with proportionally more palmitic, stearic, and oleic acids, and less of the longer and more desaturated homologs. Histological analysis of aborted rst1 seeds revealed that embryo development terminates at the approximate heart-shaped stage, whereas viable rst1 and wild-type embryos develop similarly. The RST1 gene encodes a predicted 1,841-amino acid novel protein with a molecular mass of 203.6 kD and a theoretical pI of 6.21. The RST1 transcript was found in all tissues examined including leaves, flowers, roots, stems, and siliques, but accumulation levels were not correlated with the degree to which different organs appeared affected by the mutation. The new RST1 gene reveals a novel genetic connection between lipid synthesis and embryo development; however, RST1's exact role is still quite unknown. The degree to which RST1 is associated with lipid signaling in development is an important focus of ongoing studies.
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Affiliation(s)
- Xinbo Chen
- Crop Gene Engineering Key Laboratory of Hunan Province, Hunan Agricultural University, Changsha, China
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158
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Costaglioli P, Joubès J, Garcia C, Stef M, Arveiler B, Lessire R, Garbay B. Profiling candidate genes involved in wax biosynthesis in Arabidopsis thaliana by microarray analysis. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1734:247-58. [PMID: 15914083 DOI: 10.1016/j.bbalip.2005.04.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2004] [Revised: 03/17/2005] [Accepted: 04/15/2005] [Indexed: 11/29/2022]
Abstract
Plant epidermal wax forms a hydrophobic layer covering aerial plant organs which constitutes a barrier against uncontrolled water loss and biotic stresses. Wax biosynthesis requires the coordinated activity of a large number of enzymes for the formation of saturated very-long-chain fatty acids and their further transformation in several aliphatic compounds. We found in the available database 282 candidate genes that may play a role in wax synthesis, regulation and transport. To identify the most interesting candidates, we measured the level of expression of 204 genes in the aerial parts of 15-day-old Arabidopsis seedlings by performing microarray experiments. We showed that only 25% of the putative candidates were expressed to significant levels in our samples, thus significantly reducing the number of genes which will be worth studying using reverse genetics to demonstrate their involvement in wax accumulation. We identified a beta-keto acyl-CoA synthase gene, At5g43760, which is co-regulated with the wax gene CER6 in a number of conditions and organs. By contrast, we showed that neither the fatty acyl-CoA reductase genes nor the wax synthase genes were expressed in 15-day-old leaves and stems, raising questions about the identity of the enzymes involved in the acyl-reduction pathway that accounts for 20% of the total wax amount.
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Affiliation(s)
- Patricia Costaglioli
- Laboratoire de Biogenèse Membranaire, CNRS, UMR 5200, Université Victor Segalen Bordeaux 2, 146 rue léo Saignat, Case 92, 33076 Bordeaux Cedex, France.
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159
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McQueen-Mason S. Cell walls: the boundaries of plant development. The role of the extracellular matrix in the control of plant development: the 13th New Phytologist Symposium, London, UK, January 2005. THE NEW PHYTOLOGIST 2005; 166:717-22. [PMID: 15869636 DOI: 10.1111/j.1469-8137.2005.01447.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Affiliation(s)
- Simon McQueen-Mason
- CNAP, Biology Department, University of York, PO Box 373, York, YO10 5YW, UK. email
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160
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Zhang JY, Broeckling CD, Blancaflor EB, Sledge MK, Sumner LW, Wang ZY. Overexpression of WXP1, a putative Medicago truncatula AP2 domain-containing transcription factor gene, increases cuticular wax accumulation and enhances drought tolerance in transgenic alfalfa (Medicago sativa). THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 42:689-707. [PMID: 15918883 DOI: 10.1111/j.1365-313x.2005.02405.x] [Citation(s) in RCA: 227] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The identification of leaf wax genes involved in stress tolerance is expected to have great potential for crop improvement. Here we report the characterization of a novel AP2 domain-containing putative transcription factor gene from the model legume Medicago truncatula. The gene, designated WXP1, is able to activate wax production and confer drought tolerance in alfalfa (Medicago sativa), the most important forage legume species in the world and a close relative of M. truncatula. The predicted protein of WXP1 has 371 aa; it is one of the longest peptides of all the single AP2 domain proteins in M. truncatula. WXP1 is distinctly different from the most studied genes in the AP2/ERF transcription factor family such as AP2s, CBF/DREB1s, DREB2s, WIN1/SHN1 and GL15. Transcript level of WXP1 is inducible by cold, abscisic acid and drought treatment mainly in shoot tissues in M. truncatula. Overexpression of WXP1 under the control of the CaMV35S promoter led to a significant increase in cuticular wax loading on leaves of transgenic alfalfa. Scanning electron microscopy revealed earlier accumulation of wax crystals on the adaxial surface of newly expanded leaves and higher densities of wax crystalline structures on both adaxial and abaxial surfaces of mature leaves. Gas chromatography-mass spectrometry analysis revealed that total leaf wax accumulation per surface area increased 29.6-37.7% in the transgenic lines, and the increase was mainly contributed by C30 primary alcohol. WXP1 overexpression induced a number of wax-related genes. Transgenic leaves showed reduced water loss and chlorophyll leaching. Transgenic alfalfa plants with increased cuticular waxes showed enhanced drought tolerance demonstrated by delayed wilting after watering was ceased and quicker and better recovery when the dehydrated plants were re-watered.
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Affiliation(s)
- Ji-Yi Zhang
- Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA
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161
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Zheng H, Rowland O, Kunst L. Disruptions of the Arabidopsis Enoyl-CoA reductase gene reveal an essential role for very-long-chain fatty acid synthesis in cell expansion during plant morphogenesis. THE PLANT CELL 2005; 17:1467-81. [PMID: 15829606 PMCID: PMC1091768 DOI: 10.1105/tpc.104.030155] [Citation(s) in RCA: 271] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Accepted: 03/15/2005] [Indexed: 05/18/2023]
Abstract
In the absence of cell migration, plant architecture is largely determined by the direction and extent of cell expansion during development. In this report, we show that very-long-chain fatty acid (VLCFA) synthesis plays an essential role in cell expansion. The Arabidopsis thaliana eceriferum10 (cer10) mutants exhibit severe morphological abnormalities and reduced size of aerial organs. These mutants are disrupted in the At3g55360 gene, previously identified as a gene coding for enoyl-CoA reductase (ECR), an enzyme required for VLCFA synthesis. The absence of ECR activity results in a reduction of cuticular wax load and affects VLCFA composition of seed triacylglycerols and sphingolipids, demonstrating in planta that ECR is involved in all VLCFA elongation reactions in Arabidopsis. Epidermal and seed-specific silencing of ECR activity resulted in a reduction of cuticular wax load and the VLCFA content of seed triacylglycerols, respectively, with no effects on plant morphogenesis, suggesting that the developmental phenotypes arise from abnormal sphingolipid composition. Cellular analysis revealed aberrant endocytic membrane traffic and defective cell expansion underlying the morphological defects of cer10 mutants.
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Affiliation(s)
- Huanquan Zheng
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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162
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Lolle SJ, Victor JL, Young JM, Pruitt RE. Genome-wide non-mendelian inheritance of extra-genomic information in Arabidopsis. Nature 2005; 434:505-9. [PMID: 15785770 DOI: 10.1038/nature03380] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Accepted: 01/21/2005] [Indexed: 11/08/2022]
Abstract
A fundamental tenet of classical mendelian genetics is that allelic information is stably inherited from one generation to the next, resulting in predictable segregation patterns of differing alleles. Although several exceptions to this principle are known, all represent specialized cases that are mechanistically restricted to either a limited set of specific genes (for example mating type conversion in yeast) or specific types of alleles (for example alleles containing transposons or repeated sequences). Here we show that Arabidopsis plants homozygous for recessive mutant alleles of the organ fusion gene HOTHEAD (HTH) can inherit allele-specific DNA sequence information that was not present in the chromosomal genome of their parents but was present in previous generations. This previously undescribed process is shown to occur at all DNA sequence polymorphisms examined and therefore seems to be a general mechanism for extra-genomic inheritance of DNA sequence information. We postulate that these genetic restoration events are the result of a template-directed process that makes use of an ancestral RNA-sequence cache.
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Affiliation(s)
- Susan J Lolle
- Department of Botany and Plant Pathology, Purdue University, 915 W. State Street, West Lafayette, Indiana 47907-2054, USA
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163
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Abstract
For pollination to succeed, pollen must carry sperm through a variety of different floral tissues to access the ovules within the pistil. The pistil provides everything the pollen requires for success in this endeavor including distinct guidance cues and essential nutrients that allow the pollen tube to traverse enormous distances along a complex path to the unfertilized ovule. Although the pistil is a great facilitator of pollen function, it can also be viewed as an elaborate barrier that shields ovules from access from inappropriate pollen, such as pollen from other species. Each discrete step taken by pollen tubes en route to the ovules is a potential barrier point to ovule access and waste by inappropriate mates. In this review, we survey the current molecular understanding of how pollination proceeds, and ask to what extent is each step important for mate discrimination. As this field progresses, this synthesis of functional biology and evolutionary studies will provide insight into the molecular basis of the species barriers that maintain the enormous diversity seen in flowering plants.
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Affiliation(s)
- Robert Swanson
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Illinois 60637, USA.
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164
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Efremova N, Schreiber L, Bär S, Heidmann I, Huijser P, Wellesen K, Schwarz-Sommer Z, Saedler H, Yephremov A. Functional conservation and maintenance of expression pattern of FIDDLEHEAD-like genes in Arabidopsis and Antirrhinum. PLANT MOLECULAR BIOLOGY 2004; 56:821-37. [PMID: 15803418 DOI: 10.1007/s11103-004-5576-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2004] [Accepted: 10/28/2004] [Indexed: 05/07/2023]
Abstract
In Arabidopsis, loss of function of the epidermis-specific FDH gene coding for a putative beta-ketoacyl-CoA synthase results in ectopic organ fusions in mutants. Corresponding mutants are not available for Antirrhinum majus, however, organ fusions can be induced in both species by chloroacetamide inhibitors of beta-ketoacyl-CoA synthases using a chemical genetics approach. We isolated the ortholog of FDH from Antirrhinum majus, the ANTIRRHINUM FIDDLEHEAD (AFI ) gene, and showed that AFI complements fdh when expressed in the epidermis under control of the FDH promoter. Like FDH, the AFI gene exhibits protodermis- and epidermis-specific expression, and its promoter directs the expression of reporter genes to the epidermis in transgenic Antirrhinum and Arabidopsis. We demonstrate down-regulation of the FDH promoter in the epidermis of the ovary septum, thereby supporting the assumption that FDH-like genes may directly facilitate the cell-cell interactions that need to occur during carpel fusion and pollen tube growth. Up-regulation of FDH in the stomium, on the other hand, provides evidence for its possible involvement in cell separation during anther dehiscence. Down-regulation of the FDH and AFI promoters in the septum is observed in transgenic Arabidopsis but not in Antirrhinum plants. This probably reflects differences in the ontogeny of the ovary septum between the two species. We also show that epidermis-specific FDH-like genes may not be able to efficiently elongate fatty acid chains when misexpressed in seeds.
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Affiliation(s)
- Nadia Efremova
- Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, 50829 Köln, Germany
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165
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Ingram GC. Between the sheets: inter-cell-layer communication in plant development. Philos Trans R Soc Lond B Biol Sci 2004; 359:891-906. [PMID: 15306405 PMCID: PMC1693377 DOI: 10.1098/rstb.2003.1356] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cells of plant meristems and embryos are arranged in an organized, and sometimes extremely beautiful, layered pattern. This pattern is maintained by the controlled orientation of cell divisions within layers. However, despite this layered structure, cell behaviour during plant development is not lineage dependent, and does not occur in a mosaic fashion. Many studies, both classical and recent, have shown that plant cell identity can be re-specified according to position, allowing plants to show remarkable developmental plasticity. However, the layered structure of meristems and the implications of this during plant development, remain subjects of some speculation. Of particular interest is the question of how cell layers communicate, and how communication between cell layers could allow coordinated developmental processes to take place. Recent research has uncovered several examples both of the molecular mechanisms by which cell layers can communicate, and of how this communication can infringe on developmental processes. A range of examples is used to illustrate the diversity of mechanisms potentially implicated in cell-layer communication during plant development.
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Affiliation(s)
- Gwyneth C Ingram
- Institute of Cell and Molecular Biology, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JR, Scotland, UK.
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166
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Aharoni A, Dixit S, Jetter R, Thoenes E, van Arkel G, Pereira A. The SHINE clade of AP2 domain transcription factors activates wax biosynthesis, alters cuticle properties, and confers drought tolerance when overexpressed in Arabidopsis. THE PLANT CELL 2004; 16:2463-80. [PMID: 15319479 PMCID: PMC520946 DOI: 10.1105/tpc.104.022897] [Citation(s) in RCA: 537] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Accepted: 05/11/2004] [Indexed: 05/17/2023]
Abstract
The interface between plants and the environment plays a dual role as a protective barrier as well as a medium for the exchange of gases, water, and nutrients. The primary aerial plant surfaces are covered by a cuticle, acting as the essential permeability barrier toward the atmosphere. It is a heterogeneous layer composed mainly of lipids, namely cutin and intracuticular wax with epicuticular waxes deposited on the surface. We identified an Arabidopsis thaliana activation tag gain-of-function mutant shine (shn) that displayed a brilliant, shiny green leaf surface with increased cuticular wax compared with the leaves of wild-type plants. The gene responsible for the phenotype encodes one member of a clade of three proteins of undisclosed function, belonging to the plant-specific family of AP2/EREBP transcription factors. Overexpression of all three SHN clade genes conferred a phenotype similar to that of the original shn mutant. Biochemically, such plants were altered in wax composition (very long fatty acid derivatives). Total cuticular wax levels were increased sixfold in shn compared with the wild type, mainly because of a ninefold increase in alkanes that comprised approximately half of the total waxes in the mutant. Chlorophyll leaching assays and fresh weight loss experiments indicated that overexpression of the SHN genes increased cuticle permeability, probably because of changes in its ultrastructure. Likewise, SHN gene overexpression altered leaf and petal epidermal cell structure, trichome number, and branching as well as the stomatal index. Interestingly, SHN overexpressors displayed significant drought tolerance and recovery, probably related to the reduced stomatal density. Expression analysis using promoter-beta-glucuronidase fusions of the SHN genes provides evidence for the role of the SHN clade in plant protective layers, such as those formed during abscission, dehiscence, wounding, tissue strengthening, and the cuticle. We propose that these diverse functions are mediated by regulating metabolism of lipid and/or cell wall components.
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Affiliation(s)
- Asaph Aharoni
- Plant Research International, 6700 AA, Wageningen, The Netherlands
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167
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Watanabe M, Tanaka H, Watanabe D, Machida C, Machida Y. The ACR4 receptor-like kinase is required for surface formation of epidermis-related tissues in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 39:298-308. [PMID: 15255860 DOI: 10.1111/j.1365-313x.2004.02132.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In higher plants, an outer layer of meristematic cells, the protoderm, forms early in embryogenesis and this layer gives rise to the epidermis in differentiating tissues. We proposed previously that an Arabidopsis thaliana homolog of crinkly4 (ACR4), a gene for a receptor-like protein kinase, would be involved in differentiation and/or maintenance of epidermis-related tissues. In the present study, we isolated loss-of-function acr4 mutants by a reverse genetic approach. Our extensive analyses using the transmission electron microscopy and the toluidine blue test -- a method that has recently been developed for the rapid visualization of defects in the leaf cuticle -- showed that the acr4 mutations significantly affected the differentiation of leaf epidermal cells, suggesting similar roles for ACR4 and CR4 in the differentiation of leaf epidermis. Our acr4 mutants also had various abnormalities related to epidermal differentiation, which included disorganized cell layers in the integument and endothelium of ovules. In addition, the green fluorescent protein fused to ACR4 was localized preferentially on the lateral and basal plasma membranes in the epidermis of the leaf primordia, suggesting a role for ACR4 in epidermal differentiation at cell surfaces that make contact with adjacent cells. Furthermore, the loss-of-function mutations in the ACR4 and ABNORMAL LEAF SHAPE1 (ALE1) genes, which encode a putative subtilisin-like serine protease, synergistically affected the function of the epidermis such that most leaves fused. Thus, ACR4 seems to play an essential role in the differentiation of proper epidermal cells in both vegetative and reproductive tissues.
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Affiliation(s)
- Masaru Watanabe
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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168
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Trenkamp S, Martin W, Tietjen K. Specific and differential inhibition of very-long-chain fatty acid elongases from Arabidopsis thaliana by different herbicides. Proc Natl Acad Sci U S A 2004; 101:11903-8. [PMID: 15277688 PMCID: PMC511072 DOI: 10.1073/pnas.0404600101] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In higher plants, very-long-chain fatty acids (VLCFAs) are the main constituents of hydrophobic polymers that prevent dessication at the leaf surface and provide stability to pollen grains. Of the 21 genes encoding VLCFA elongases (VLCFAEs) from Arabidopsis thaliana, 17 were expressed heterologously in Saccharomyces cerevisiae. Six VLCFAEs, including three known elongases (FAE1, KCS1, and KCS2) and three previously uncharacterized gene products (encoded by At5g43760, At1g04220, and At1g25450) were found to be enzymatically active with endogenous yeast fatty acid substrates and to some extent with externally supplied unsaturated substrates. The spectrum of VLCFAs accumulated in expressing yeast strains was determined by gas chromatography/mass spectrometry. Marked specificity was found among elongases tested with respect to their elongation products, which encompassed saturated and monounsaturated fatty acids 20-30 carbon atoms in length. The active VLCFAEs revealed highly distinct patterns of differential sensitivity to oxyacetamides, chloroacetanilides, and other compounds tested, whereas yeast endogenous VLCFA production, which involves its unrelated elongase (ELO) in sphingolipid synthesis, was unaffected. Several compounds inhibited more than one VLCFAE, and some inhibited all six active enzymes. These findings pinpoint VLCFAEs as the target of the widely used K(3) class herbicides, which have been in commercial use for 50 years, provide important clues as to why spontaneous resistance to this class is rare, and point to complex patterns of substrate specificity and product spectrum among members of the Arabidopsis VLCFAE family.
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Affiliation(s)
- Sandra Trenkamp
- Bayer CropScience AG, Target Research, Building 6240, 40789 Monheim, Germany
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169
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DUNN TERESAM, LYNCH DANIELV, MICHAELSON LOUISEV, NAPIER JOHNATHANA. A post-genomic approach to understanding sphingolipid metabolism in Arabidopsis thaliana. ANNALS OF BOTANY 2004; 93:483-97. [PMID: 15037448 PMCID: PMC4242313 DOI: 10.1093/aob/mch071] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
AIMS To highlight the importance of sphingolipids and their metabolites in plant biology. SCOPE The completion of the arabidopsis genome provides a platform for the identification and functional characterization of genes involved in sphingolipid biosynthesis. Using the yeast Saccharomyces cerevisiae as an experimental model, this review annotates arabidopsis open reading frames likely to be involved in sphingolipid metabolism. A number of these open reading frames have already been subject to functional characterization, though the majority still awaits investigation. Plant-specific aspects of sphingolipid biology (such as enhanced long chain base heterogeneity) are considered in the context of the emerging roles for these lipids in plant form and function. CONCLUSIONS Arabidopsis provides an excellent genetic and post-genomic model for the characterization of the roles of sphingolipids in higher plants.
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Affiliation(s)
- TERESA M. DUNN
- Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
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170
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Groover A, Fontana JR, Dupper G, Ma C, Martienssen R, Strauss S, Meilan R. Gene and enhancer trap tagging of vascular-expressed genes in poplar trees. PLANT PHYSIOLOGY 2004; 134:1742-51. [PMID: 15051863 PMCID: PMC419847 DOI: 10.1104/pp.103.034330] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Revised: 01/01/2004] [Accepted: 01/04/2004] [Indexed: 05/18/2023]
Abstract
We report a gene discovery system for poplar trees based on gene and enhancer traps. Gene and enhancer trap vectors carrying the beta-glucuronidase (GUS) reporter gene were inserted into the poplar genome via Agrobacterium tumefaciens transformation, where they reveal the expression pattern of genes at or near the insertion sites. Because GUS expression phenotypes are dominant and are scored in primary transformants, this system does not require rounds of sexual recombination, a typical barrier to developmental genetic studies in trees. Gene and enhancer trap lines defining genes expressed during primary and secondary vascular development were identified and characterized. Collectively, the vascular gene expression patterns revealed that approximately 40% of genes expressed in leaves were expressed exclusively in the veins, indicating that a large set of genes is required for vascular development and function. Also, significant overlap was found between the sets of genes responsible for development and function of secondary vascular tissues of stems and primary vascular tissues in other organs of the plant, likely reflecting the common evolutionary origin of these tissues. Chromosomal DNA flanking insertion sites was amplified by thermal asymmetric interlaced PCR and sequenced and used to identify insertion sites by reference to the nascent Populus trichocarpa genome sequence. Extension of the system was demonstrated through isolation of full-length cDNAs for five genes of interest, including a new class of vascular-expressed gene tagged by enhancer trap line cET-1-pop1-145. Poplar gene and enhancer traps provide a new resource that allows plant biologists to directly reference the poplar genome sequence and identify novel genes of interest in forest biology.
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Affiliation(s)
- Andrew Groover
- Institute of Forest Genetics, Pacific Southwest Research Station, USDA Forest Service, Davis, California 95616, USA.
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171
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Broun P, Poindexter P, Osborne E, Jiang CZ, Riechmann JL. WIN1, a transcriptional activator of epidermal wax accumulation in Arabidopsis. Proc Natl Acad Sci U S A 2004; 101:4706-11. [PMID: 15070782 PMCID: PMC384811 DOI: 10.1073/pnas.0305574101] [Citation(s) in RCA: 277] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2003] [Indexed: 11/18/2022] Open
Abstract
Epicuticular wax forms a layer of hydrophobic material on plant aerial organs, which constitutes a protective barrier between the plant and its environment. We report here the identification of WIN1, an Arabidopsis thaliana ethylene response factor-type transcription factor, which can activate wax deposition in overexpressing plants. We constitutively expressed WIN1 in transgenic Arabidopsis plants, and found that leaf epidermal wax accumulation was up to 4.5-fold higher in these plants than in control plants. A significant increase was also found in stems. Interestingly, approximately 50% of the additional wax could only be released by complete lipid extractions, suggesting that not all of the wax is superficial. Gene expression analysis indicated that a number of genes, such as CER1, KCS1, and CER2, which are known to be involved in wax biosynthesis, were induced in WIN1 overexpressors. This observation indicates that induction of wax accumulation in transgenic plants is probably mediated through an increase in the expression of genes encoding enzymes of the wax biosynthesis pathway.
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Affiliation(s)
- Pierre Broun
- Mendel Biotechnology, 21375 Cabot Boulevard, Hayward, CA 94545, USA.
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172
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Schnurr J, Shockey J, Browse J. The acyl-CoA synthetase encoded by LACS2 is essential for normal cuticle development in Arabidopsis. THE PLANT CELL 2004; 16:629-42. [PMID: 14973169 PMCID: PMC385277 DOI: 10.1105/tpc.017608] [Citation(s) in RCA: 267] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2003] [Accepted: 12/27/2003] [Indexed: 05/18/2023]
Abstract
Long-chain acyl-CoA synthetase (LACS) activities are encoded by a family of at least nine genes in Arabidopsis (Arabidopsis thaliana). These enzymes have roles in lipid synthesis, fatty acid catabolism, and the transport of fatty acids between subcellular compartments. Here, we show that the LACS2 gene (At1g49430) is expressed in young, rapidly expanding tissues, and in leaves expression is limited to cells of the adaxial and abaxial epidermal layers, suggesting that the LACS2 enzyme may act in the synthesis of cutin or cuticular waxes. A lacs2 null mutant was isolated by reverse genetics. Leaves of mutant plants supported pollen germination and released chlorophyll faster than wild-type leaves when immersed in 80% ethanol, indicating a defect in the cuticular barrier. The composition of surface waxes extracted from lacs2 leaves was similar to the wild type, and the total wax load was higher than the wild type (111.4 microg/dm(2) versus 76.4 microg/dm(2), respectively). However, the thickness of the cutin layer on the abaxial surface of lacs2 leaves was only 22.3 +/- 1.7 nm compared with 33.0 +/- 2.0 nm for the wild type. In vitro assays showed that 16-hydroxypalmitate was an excellent substrate for recombinant LACS2 enzyme. We conclude that the LACS2 isozyme catalyzes the synthesis of omega-hydroxy fatty acyl-CoA intermediates in the pathway to cutin synthesis. The lacs2 phenotype, like the phenotypes of some other cutin mutants, is very pleiotropic, causing reduced leaf size and plant growth, reduced seed production, and lower rates of seedling germination and establishment. The LACS2 gene and the corresponding lacs2 mutant will help in future studies of the cutin synthesis pathway and in understanding the consequences of reduced cutin production on many aspects of plant biology.
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Affiliation(s)
- Judy Schnurr
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
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173
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Tanaka T, Tanaka H, Machida C, Watanabe M, Machida Y. A new method for rapid visualization of defects in leaf cuticle reveals five intrinsic patterns of surface defects in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 37:139-46. [PMID: 14675439 DOI: 10.1046/j.1365-313x.2003.01946.x] [Citation(s) in RCA: 202] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The epidermis of higher plants generates the cuticle layer that covers the outer surface of each plant. The cuticle plays a crucial role in plant development, and some mutants with defective cuticle exhibit morphological abnormalities, such as the fusion of organs. The way in which the cuticle forms and its contribution to morphogenesis are poorly understood. Conventional detection of the cuticle by transmission electron microscopy (TEM) requires laborious procedures, which include fixation, staining with osmium, and preparation of ultra-thin sections. It is also difficult to survey entire surfaces of expanded leaves because of the limited size of specimens that can be examined. Thus, TEM is unsuitable for large-scale screening for mutants with defective cuticle. We describe here a rapid and inexpensive method, designated the toluidine-blue (TB) test, for detection of cuticular defects in whole leaves. We demonstrated the validity of the TB test using mutants of Arabidopsis thaliana, including abnormal leaf shape1 (ale1), fiddlehead (fdh), and five eceriferum (cer) mutants, in which the structure and/or function of the cuticle is abnormal. Genetic screening for mutants using the TB test allowed us to identify seven loci. The cuticle-defective regions of leaves of the mutants revealed five intrinsic patterns of surface defects (classes I through V), suggesting that formation of functional cuticle on leaves involves various spatially regulated factors.
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Affiliation(s)
- Toshihiro Tanaka
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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174
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Edlund AF, Swanson R, Preuss D. Pollen and stigma structure and function: the role of diversity in pollination. THE PLANT CELL 2004; 16 Suppl:S84-97. [PMID: 15075396 PMCID: PMC2643401 DOI: 10.1105/tpc.015800] [Citation(s) in RCA: 319] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Affiliation(s)
- Anna F Edlund
- Howard Hughes Medical Institute, Molecular Genetics and Cell Biology Department, University of Chicago, Chicago, Illinois 60637, USA
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175
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Edlund AF, Swanson R, Preuss D. Pollen and stigma structure and function: the role of diversity in pollination. THE PLANT CELL 2004. [PMID: 15075396 DOI: 10.1105/tpc.015800.pollen] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Affiliation(s)
- Anna F Edlund
- Howard Hughes Medical Institute, Molecular Genetics and Cell Biology Department, University of Chicago, Chicago, Illinois 60637, USA
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176
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Wang A, Xia Q, Xie W, Datla R, Selvaraj G. The classical Ubisch bodies carry a sporophytically produced structural protein (RAFTIN) that is essential for pollen development. Proc Natl Acad Sci U S A 2003; 100:14487-92. [PMID: 14612572 PMCID: PMC283618 DOI: 10.1073/pnas.2231254100] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2003] [Accepted: 09/11/2003] [Indexed: 11/18/2022] Open
Abstract
Pollen fecundity is crucial to crop productivity and also to biodiversity in general. Pollen development is supported by the tapetum, a metabolically active sporophytic nurse layer that devotes itself to this process. The tapetum in cereals and a vast majority of other plants is of the nonamoeboid type. Unable to reach out to microspores, it secretes nutrients into the anther locule where the microspores reside and develop. Orbicules (Ubisch bodies), studied in various plants since their discovery approximately 140 years ago, are a hallmark of the secretory tapetum. Their significance to tapetal or pollen development has not been established. We have identified in wheat and rice an anther-specific single-copy gene (per haploid genome equivalent) whose suppression in rice by RNA interference nearly eliminated the seed set. The flowers in the transgenics were normal for female functions, but the pollen collapsed and became less viable. Further characterization of the gene product, named RAFTIN, in wheat has shown that it is present in pro-orbicule bodies and it is accumulated in Ubisch bodies. Furthermore, it is targeted to microspore exine. Although the carboxyl portion of RAFTINs shares short, dispersed amino acid sequences (BURP domain) in common with a variety of proteins of disparate biological contexts, the occurrence RAFTIN per se is limited to cereals; neither the Arabidopsis genome nor the vast collection of ESTs suggests any obvious dicot homologs. Furthermore, our results show that RAFTIN is essential for the late phase of pollen development in cereals.
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Affiliation(s)
- Aiming Wang
- Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9
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177
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Rhee SY, Osborne E, Poindexter PD, Somerville CR. Microspore separation in the quartet 3 mutants of Arabidopsis is impaired by a defect in a developmentally regulated polygalacturonase required for pollen mother cell wall degradation. PLANT PHYSIOLOGY 2003; 133:1170-80. [PMID: 14551328 PMCID: PMC281612 DOI: 10.1104/pp.103.028266] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2003] [Revised: 07/16/2003] [Accepted: 08/03/2003] [Indexed: 05/18/2023]
Abstract
Mutations in the QUARTET loci in Arabidopsis result in failure of microspore separation during pollen development due to a defect in degradation of the pollen mother cell wall during late stages of pollen development. Mutations in a new locus required for microspore separation, QRT3, were isolated, and the corresponding gene was cloned by T-DNA tagging. QRT3 encodes a protein that is approximately 30% similar to an endopolygalacturonase from peach (Prunus persica). The QRT3 protein was expressed in yeast (Saccharomyces cerevisiae) and found to exhibit polygalacturonase activity. In situ hybridization experiments showed that QRT3 is specifically and transiently expressed in the tapetum during the phase when microspores separate from their meiotic siblings. Immunohistochemical localization of QRT3 indicated that the protein is secreted from tapetal cells during the early microspore stage. Thus, QRT3 plays a direct role in degrading the pollen mother cell wall during microspore development.
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Affiliation(s)
- Seung Y Rhee
- Carnegie Institution, Department of Plant Biology, 260 Panama Street, Stanford, California 94305, USA
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178
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Lequeu J, Fauconnier ML, Chammaï A, Bronner R, Blée E. Formation of plant cuticle: evidence for the occurrence of the peroxygenase pathway. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 36:155-64. [PMID: 14535881 DOI: 10.1046/j.1365-313x.2003.01865.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Cuticle plays a major role as a protective barrier in plants. Despite its physiological importance, the mode of formation of this complex structure remains poorly understood. In particular, none of the putative enzymes involved in the biosynthesis of the cutin, the matrix of cuticle, have been cloned. We have shown previously that peroxygenase is able to catalyze in vitro the epoxidation step required for the biosynthesis of C18 cutin monomers. In the present work, we have confirmed in planta that this oxidase is indeed a key enzyme involved in the formation of cutin. Thus, in maize leaves, the specific inactivation of peroxygenase by organophosphorothioates resulted in a dramatic decrease of cuticular epoxide content, as visualized by a specific histochemical technique that was accompanied by a reduced thickness of the cuticle. A strict correlation could also be established between the extent of inhibition of the peroxygenase and the modification of the cuticle triggered by a family of structurally related inhibitors. Importantly, these effects were restricted to plants that contain a cutin originating from C18 monomers. The altered cuticle of maize, treated with the peroxygenase inhibitor, was characterized by an increased permeability to pesticides. In addition, such plants became largely susceptible to infection by fungi, implying that the cuticle represents a crucial target for the modulation of the response in plant-pathogen interactions.
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Affiliation(s)
- José Lequeu
- Laboratoire des Phytooxylipines, IBMP-CNRS-UPR 2357, 28-Rue Goethe, 67083 Strasbourg-Cedex, France
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179
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Kurata T, Kawabata-Awai C, Sakuradani E, Shimizu S, Okada K, Wada T. The YORE-YORE gene regulates multiple aspects of epidermal cell differentiation in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 36:55-66. [PMID: 12974811 DOI: 10.1046/j.1365-313x.2003.01854.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We have identified a new Arabidopsis mutant, yore-yore (yre), which has small trichomes and glossy stems. Adhesion between epidermal cells was observed in the organs of the yre shoot. The cloned YRE had high homology to plant genes involved in epicuticular wax synthesis, such as ECERIFERUM1 (CER1) and maize GLOSSY1. The phenotype of transgenic plants harboring double-stranded RNA interference (dsRNAi) YRE was quite similar to that of the yre mutant. The amount of epicuticular wax extracted from leaves and stems of yre-1 was approximately one-sixth of that from the wild type. YRE promoter::GUS and in situ hybridization revealed that YRE was specifically expressed in cells of the L1 layer of the shoot apical meristem and young leaves, stems, siliques, and lateral root primordia. Strong expression was detected in developing trichomes. The trichome structure of cer1 was normal, whereas that of the yre cer1 double mutant was heavily deformed, indicating that epicuticular wax is required for normal growth of trichomes. Double mutants of yre and trichome-morphology mutants, glabra2 (gl2) and transparent testa glabra1 (ttg1), showed that the phenotype of the trichome structure was additive, suggesting that the wax-requiring pathway is distinct from the trichome development pathway controlled by GL2 and TTG1.
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Affiliation(s)
- Tetsuya Kurata
- Plant Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
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180
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Krolikowski KA, Victor JL, Wagler TN, Lolle SJ, Pruitt RE. Isolation and characterization of the Arabidopsis organ fusion gene HOTHEAD. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 35:501-11. [PMID: 12904212 DOI: 10.1046/j.1365-313x.2003.01824.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The outer epidermal plant cell wall and cuticle play an important role in regulating both abiotic and biotic interactions between the plant and its environment. In addition to acting as a protective barrier that limits water loss, the effects of detrimental irradiation and invasion by pathogens, the epidermis also offers an interface that is inert to interactions between organs and ensures proper separation and expansion of organs at the growing points of the plant. Here, we describe the molecular cloning and characterization of HOTHEAD (HTH), a gene required to limit cellular interactions between contacting epidermal cells during floral development. HTH is a member of a small gene family in Arabidopsis and encodes an enzyme related to a group of FAD-containing oxidoreductases that have been described in several other species. Characterization of 11 independently derived mutant alleles suggests that key amino acids are shared between these related groups of enzymes and identify a cluster of other functionally important residues that are highly conserved only within the Arabidopsis gene family. Our findings add this new type of enzyme to a growing list of enzymes that have been shown to be involved in regulating post-genital organ fusion. Expression analysis of the HTH gene shows that it is expressed in all tissues tested, including roots, and is not epidermis-specific. Furthermore, the sequence data unequivocally show that none of the alleles isolated are epigenetic alleles as suggested by genetic behavior previously observed at this locus.
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Affiliation(s)
- Katherine A Krolikowski
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907-1155, USA
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181
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Beisson F, Koo AJK, Ruuska S, Schwender J, Pollard M, Thelen JJ, Paddock T, Salas JJ, Savage L, Milcamps A, Mhaske VB, Cho Y, Ohlrogge JB. Arabidopsis genes involved in acyl lipid metabolism. A 2003 census of the candidates, a study of the distribution of expressed sequence tags in organs, and a web-based database. PLANT PHYSIOLOGY 2003; 132:681-97. [PMID: 12805597 PMCID: PMC167007 DOI: 10.1104/pp.103.022988] [Citation(s) in RCA: 260] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2003] [Revised: 03/25/2003] [Accepted: 03/28/2003] [Indexed: 05/17/2023]
Abstract
The genome of Arabidopsis has been searched for sequences of genes involved in acyl lipid metabolism. Over 600 encoded proteins have been identified, cataloged, and classified according to predicted function, subcellular location, and alternative splicing. At least one-third of these proteins were previously annotated as "unknown function" or with functions unrelated to acyl lipid metabolism; therefore, this study has improved the annotation of over 200 genes. In particular, annotation of the lipolytic enzyme group (at least 110 members total) has been improved by the critical examination of the biochemical literature and the sequences of the numerous proteins annotated as "lipases." In addition, expressed sequence tag (EST) data have been surveyed, and more than 3,700 ESTs associated with the genes were cataloged. Statistical analysis of the number of ESTs associated with specific cDNA libraries has allowed calculation of probabilities of differential expression between different organs. More than 130 genes have been identified with a statistical probability > 0.95 of preferential expression in seed, leaf, root, or flower. All the data are available as a Web-based database, the Arabidopsis Lipid Gene database (http://www.plantbiology.msu.edu/lipids/genesurvey/index.htm). The combination of the data of the Lipid Gene Catalog and the EST analysis can be used to gain insights into differential expression of gene family members and sets of pathway-specific genes, which in turn will guide studies to understand specific functions of individual genes.
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Affiliation(s)
- Frédéric Beisson
- Department of Plant Biology, Michigan State University, East Lansing 48824, USA
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182
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Chen X, Goodwin SM, Boroff VL, Liu X, Jenks MA. Cloning and characterization of the WAX2 gene of Arabidopsis involved in cuticle membrane and wax production. THE PLANT CELL 2003; 15:1170-85. [PMID: 12724542 PMCID: PMC153724 DOI: 10.1105/tpc.010926] [Citation(s) in RCA: 293] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2003] [Accepted: 03/07/2003] [Indexed: 05/18/2023]
Abstract
Insertional mutagenesis of Arabidopsis ecotype C24 was used to identify a novel mutant, designated wax2, that had alterations in both cuticle membrane and cuticular waxes. Arabidopsis mutants with altered cuticle membrane have not been reported previously. Compared with the wild type, the cuticle membrane of wax2 stems weighed 20.2% less, and when viewed using electron microscopy, it was 36.4% thicker, less opaque, and structurally disorganized. The total wax amount on wax2 leaves and stems was reduced by >78% and showed proportional deficiencies in the aldehydes, alkanes, secondary alcohols, and ketones, with increased acids, primary alcohols, and esters. Besides altered cuticle membranes, wax2 displayed postgenital fusion between aerial organs (especially in flower buds), reduced fertility under low humidity, increased epidermal permeability, and a reduction in stomatal index on adaxial and abaxial leaf surfaces. Thus, wax2 reveals a potential role for the cuticle as a suppressor of postgenital fusion and epidermal diffusion and as a mediator of both fertility and the development of epidermal architecture (via effects on stomatal index). The cloned WAX2 gene (verified by three independent allelic insertion mutants with identical phenotypes) codes for a predicted 632-amino acid integral membrane protein with a molecular mass of 72.3 kD and a theoretical pI of 8.78. WAX2 has six transmembrane domains, a His-rich diiron binding region at the N-terminal region, and a large soluble C-terminal domain. The N-terminal portion of WAX2 is homologous with members of the sterol desaturase family, whereas the C terminus of WAX2 is most similar to members of the short-chain dehydrogenase/reductase family. WAX2 has 32% identity to CER1, a protein required for wax production but not for cuticle membrane production. Based on these analyses, we predict that WAX2 has a metabolic function associated with both cuticle membrane and wax synthesis. These studies provide new insight into the genetics and biochemistry of plant cuticle production and elucidate new associations between the cuticle and diverse aspects of plant development.
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Affiliation(s)
- Xinbo Chen
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907, USA
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183
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Traidl-Hoffmann C, Kasche A, Menzel A, Jakob T, Thiel M, Ring J, Behrendt H. Impact of pollen on human health: more than allergen carriers? Int Arch Allergy Immunol 2003; 131:1-13. [PMID: 12759483 DOI: 10.1159/000070428] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The transfer of pollen from floral anther to recipient stigma is the critical reproductive event among higher plants--this is the botanical view of pollen. Proteins and glycoproteins from pollen can function as allergens, environmental molecules interacting with the human immune system to elicit an allergic response in susceptible individuals--this is how allergists and immunologists see pollen grains. Between 10 and 25% of the population now have symptoms of hay fever or allergic asthma and the incidence has more than doubled in the past three decades while the reason(s) for this increment are only hypothetical, but there is a multitude of them. Despite our natural focus on this impact of pollen on human health, pollen have to be considered in a larger context. First of all, to evaluate the bioavailability of allergens from pollen, we have to understand their function and their influence factors. Furthermore, pollen grains are not only releasing proteins eliciting specific immune responses, but they also liberate bioactive lipid mediators and this much more rapidly. And last but not least, recent observations indicate, that pollen do not only induce allergy and thus have a much broader impact on human health. This review is an attempt to favour this holistic view of pollen and their impact on human health.
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Affiliation(s)
- Claudia Traidl-Hoffmann
- Division of Environmental Dermatology and Allergy GSF--National Research Center for Environment and Health Neuherberg/Technical University of Munich, Munich, Germany.
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184
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Heredia A. Biophysical and biochemical characteristics of cutin, a plant barrier biopolymer. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1620:1-7. [PMID: 12595066 DOI: 10.1016/s0304-4165(02)00510-x] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cutin is a support biopolyester involved in waterproofing the leaves and fruits of higher plants, regulating the flow of nutrients among various plant cells and organs, and minimizing the deleterious impact of pathogens. Despite the complexity and intractable nature of this biopolymer, significant progress in chemical composition, molecular architecture and, more recently, biosynthesis have been made in the past 10 years. This review is focused in the description of these advances and their physiological impacts to improve our knowledge on plant cutin, an unusual topic in most plant physiology and biochemistry books and reviews.
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Affiliation(s)
- Antonio Heredia
- Facultad de Ciencias, Grupo de Caracterización y Síntesis de Biopolímeros Vegetales, Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, Campus de Teatinos, Spain.
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185
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Bird SM, Gray JE. Signals from the cuticle affect epidermal cell differentiation. THE NEW PHYTOLOGIST 2003; 157:9-23. [PMID: 33873705 DOI: 10.1046/j.1469-8137.2003.00543.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Studies of Arabidopsis wax biosynthesis mutants indicate that the control of cell fate in the aerial epidermis is dependant upon the synthesis of the waxy cuticle that overlies the epidermal layer. Several cer mutants, originally isolated as wax deficient, not only affect cuticular wax composition but also exhibit large increases in stomatal numbers. Stomatal numbers are also affected in hic mutant plants, but despite HIC encoding a putative wax biosynthetic enzyme the hic phenotype of increased stomatal numbers is more subtle, and only seen at elevated CO2 concentrations. This suggests that environmental effects on stomatal number may be mediated through cuticular wax composition. Other putative wax biosynthetic genes, FDH and LCR, have effects on the number of trichomes that develop in the epidermis, indicating that trichome development may also be affected by cuticle composition. Thus signals from the cuticle may influence how trichome and stomatal numbers in the epidermis are determined. Wax components could be the developmental signalling molecules, or could be the mediating medium for such signals, stimulated by environmental cues, which affect epidermal cell fate. Contents Summary 9 I. Introduction 10 II. Cuticle structure 10 III. Cuticular waxes 10 IV. Cell patterning in the epidermis 11 V. Stomatal development 12 VI. Stomatal development in dicotyledonous plants 12 VII. Mutants in stomatal development 14 VIII. Control of Stomatal Development 14 IX. Cuticle composition affects stomatal development 14 X. The HIC - HI gh Carbon dioxide gene 15 XI. Fatty acid elongases 17 XII. The cuticle: an alternative signalling medium? 17 XIII. Trichome development 18 XIV. Cuticle composition affects trichome development 19 XV. Cuticle composition affects pollen germination 20 XVI. Conclusions 20 Acknowledgements 21 References 21.
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Affiliation(s)
- Susannah M Bird
- Department of Animal and Plant Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Julie E Gray
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
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186
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Bellec Y, Harrar Y, Butaeye C, Darnet S, Bellini C, Faure JD. Pasticcino2 is a protein tyrosine phosphatase-like involved in cell proliferation and differentiation in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 32:713-22. [PMID: 12472687 DOI: 10.1046/j.1365-313x.2002.01456.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The pasticcino2 (pas2) mutant shows impaired embryo and seedling development associated with cell de-differentiation and proliferation. This process is specifically enhanced in presence of cytokinins leading to callus-like structure of the apical part of the seedling. Cell proliferation concerns localized and stochastic nodules of dividing cells. In absence of cytokinins, cell proliferation leads to small calli on stems but, most often, cell proliferation is associated with post-genital organ fusion. The PAS2 gene was identified by positional cloning. PAS2 expression was found in every plant organ and was not regulated by PAS1 and PAS3 genes. PAS2 encodes the Arabidopsis member of the protein tyrosine phosphatase-like (Ptpl) family, a new PTP family originally described in mice and humans and characterized by a mutated PTP active site. This family of proteins has a yeast homolog that is essential for cell viability. The absence of yeast PAS2 homolog can be functionally replaced by the Arabidopsis PAS2 protein, demonstrating that PAS2 function is conserved between higher and lower eukaryotes.
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Affiliation(s)
- Yannick Bellec
- Laboratoire de Biologie Cellulaire, INRA, route de St. Cyr, 78026 Versailles Cedex, France
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187
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Katavic V, Mietkiewska E, Barton DL, Giblin EM, Reed DW, Taylor DC. Restoring enzyme activity in nonfunctional low erucic acid Brassica napus fatty acid elongase 1 by a single amino acid substitution. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5625-31. [PMID: 12423362 DOI: 10.1046/j.1432-1033.2002.03270.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Genomic fatty acid elongation 1 (FAE1) clones from high erucic acid (HEA) Brassica napus, Brassica rapa and Brassica oleracea, and low erucic acid (LEA) B. napus cv. Westar, were amplified by PCR and expressed in yeast cells under the control of the strong galactose-inducible promoter. As expected, yeast cells expressing the FAE1 genes from HEA Brassica spp. synthesized very long chain monounsaturated fatty acids that are not normally found in yeast, while fatty acid profiles of yeast cells expressing the FAE1 gene from LEA B. napus were identical to control yeast samples. In agreement with published findings regarding different HEA and LEA B. napus cultivars, comparison of FAE1 protein sequences from HEA and LEA Brassicaceae revealed one crucial amino acid difference: the serine residue at position 282 of the HEA FAE1 sequences is substituted by phenylalanine in LEA B. napus cv. Westar. Using site directed mutagenesis, the phenylalanine 282 residue was substituted with a serine residue in the FAE1 polypeptide from B. napus cv. Westar, the mutated gene was expressed in yeast and GC analysis revealed the presence of very long chain monounsaturated fatty acids (VLCMFAs), indicating that the elongase activity was restored in the LEA FAE1 enzyme by the single amino acid substitution. Thus, for the first time, the low erucic acid trait in canola B. napus can be attributed to a single amino acid substitution which prevents the biosynthesis of the eicosenoic and erucic acids.
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Affiliation(s)
- Vesna Katavic
- Saskatchewan Wheat Pool Agricultural Research and Development, Saskatoon, Canada.
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188
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Blacklock BJ, Jaworski JG. Studies into factors contributing to substrate specificity of membrane-bound 3-ketoacyl-CoA synthases. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:4789-98. [PMID: 12354110 DOI: 10.1046/j.1432-1033.2002.03176.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We are interested in constructing a model for the substrate-binding site of fatty acid elongase-1 3-ketoacyl CoA synthase (FAE1 KCS), the enzyme responsible for production of very long chain fatty acids of plant seed oils. Arabidopsis thaliana and Brassica napus FAE1 KCS enzymes are highly homologous but the seed oil content of these plants suggests that their substrate specificities differ with respect to acyl chain length. We used in vivo and in vitro assays of Saccharomyces cerevisiae-expressed FAE1 KCSs to demonstrate that the B. napus FAE1 KCS enzyme favors longer chain acyl substrates than the A. thaliana enzyme. Domains/residues responsible for substrate specificity were investigated by determining catalytic activity and substrate specificity of chimeric enzymes of A. thaliana and B. napus FAE1 KCS. The N-terminal region, excluding the transmembrane domain, was shown to be involved in substrate specificity. One chimeric enzyme that included A. thaliana sequence from the N terminus to residue 114 and B. napus sequence from residue 115 to the C terminus had substrate specificity similar to that of A. thaliana FAE1 KCS. However, a K92R substitution in this chimeric enzyme changed the specificity to that of the B. napus enzyme without loss of catalytic activity. Thus, this study was successful in identifying a domain involved in determining substrate specificity in FAE1 KCS and in engineering an enzyme with novel activity.
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Affiliation(s)
- Brenda J Blacklock
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA.
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189
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Jenks MA, Eigenbrode SD, Lemieux B. Cuticular waxes of Arabidopsis. THE ARABIDOPSIS BOOK 2002; 1:e0016. [PMID: 22303194 PMCID: PMC3243341 DOI: 10.1199/tab.0016] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
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190
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Hooker TS, Millar AA, Kunst L. Significance of the expression of the CER6 condensing enzyme for cuticular wax production in Arabidopsis. PLANT PHYSIOLOGY 2002; 129:1568-80. [PMID: 12177469 PMCID: PMC166744 DOI: 10.1104/pp.003707] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Revised: 03/24/2002] [Accepted: 04/11/2002] [Indexed: 05/18/2023]
Abstract
To learn more about the role of the CER6 condensing enzyme in Arabidopsis surface wax production, we determined CER6 transcription domains and the timing of CER6 transcription in vegetative and reproductive structures from juvenile, mature, and senescing tissues. We found that CER6 is highly transcribed throughout development, exclusively in the epidermal cells in all tissues examined. The only exception to the epidermal expression was observed in anthers nearing maturity, in which CER6 mRNA was localized in the tapetum. To determine if environmental factors such as light and water deficit, which are known to stimulate wax accumulation, induce CER6 transcription, we examined the effects of these factors on CER6 transcript abundance. Our results demonstrate that light is essential for CER6 transcription, and that osmotic stress and the presence of abscisic acid enhance CER6 transcript accumulation. CER6 promoter-directed expression of the beta-glucuronidase reporter gene in transgenic plants demonstrated that the CER6 promoter was highly effective in directing epidermis-specific expression in Arabidopsis and tobacco (Nicotiana tabacum). Furthermore, CER6 promoter-driven CER6 overexpression resulted in increased wax deposition in Arabidopsis stems. These experiments indicate that the expression level of CER6 in the epidermis is one of the factors controlling wax accumulation on Arabidopsis stems.
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Affiliation(s)
- Tanya S Hooker
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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191
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Rudall PJ, Bateman RM. Roles of synorganisation, zygomorphy and heterotopy in floral evolution: the gynostemium and labellum of orchids and other lilioid monocots. Biol Rev Camb Philos Soc 2002; 77:403-41. [PMID: 12227521 DOI: 10.1017/s1464793102005936] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A gynostemium, comprising stamen filaments adnate to a syncarpous style, occurs in only threc groups of monocots: the large family Orchidaceae (Asparagales) and two small genera Pauridia (Hypoxidaceae: Asparagales) and Corsia (Corsiaceae, probably in Liliales), all epigynous taxa. Pauridia has actinomorphic (polysymmetric) flowers, whereas those of Corsia and most orchids are strongly zygomorphic (monosymmetric) with a well-differentiated labellum. In Corsia the labellum is formed from the outer median tepal (sepal), whereas in orchids it is formed from the inner median tepal (petal) and is developmentally adaxial (but positionally abaxial in orchids with resupinate flowers). Furthermore, in orchids zygomorphy is also expressed in the stamen whorls, in contrast to Corsia. In Pauridia a complete stamen whorl is suppressed, but the 'lost' outer whorl is fused to the style. The evolution of adnation and zygomorphy are discussed in the context of the existing phylogenetic framework in monocotyledons. An arguably typological classification of floral terata is presented, focusing on three contrasting modes each of peloria and pseudopeloria. Dynamic evolutionary transitions in floral morphology are assigned to recently revised concepts of heterotopy (including homeosis) and heterochrony, seeking patterns that delimit developmental constraints and allow inferences regarding underlying genetic controls. Current evidence suggests that lateral heterotopy is more frequent than acropetal heterotopy, and that full basipetal heterotopy does not occur. Pseudopeloria is more likely to generate a radically altered yet functional perianth, but is also more likely to cause acropetal modification of the gynostemium. These comparisons indicate that there are at least two key genes or sets of genes controlling adnation, adaxial stamen suppression and labellum development in lilioid monocots; at least one is responsible for stamen adnation to the style (i.e. gynostemium formation), and another controls adaxial stamen suppression and adaxial labellum formation in orchids. Stamen adnation to the style may be a product of over-expression of the genes related to epigyny (i.e. a form of hyper-epigyny). If, as seems likely, stamen-style adnation preceded zygomorphy in orchid evolution, then the flowers of Pauridia may closely resemble those of the immediate ancestors of Orchidaceae, although existing molecular phylogenetic data indicate that a sister-group relationship is unlikely. The initial radiation in Orchidaceae can be attributed to the combination of hyper-epigyny, zygomorphy and resupination, but later radiations at lower taxonomic levels that generated the remarkable species richness of subfamilies Orchidoideae and Epidendroideae are more likely to reflect more subtle innovations that directly influence pollinator specificity, such as the development of stalked pollinaria and heavily marked and/or spur-bearing labella.
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192
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Marsch-Martinez N, Greco R, Van Arkel G, Herrera-Estrella L, Pereira A. Activation tagging using the En-I maize transposon system in Arabidopsis. PLANT PHYSIOLOGY 2002; 129:1544-56. [PMID: 12177467 PMCID: PMC166742 DOI: 10.1104/pp.003327] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2002] [Revised: 02/26/2002] [Accepted: 04/08/2002] [Indexed: 05/19/2023]
Abstract
A method for the generation of stable activation tag inserts was developed in Arabidopsis using the maize (Zea mays) En-I transposon system. The method employs greenhouse selectable marker genes that are useful to efficiently generate large populations of insertions. A population of about 8,300 independent stable activation tag inserts has been produced. Greenhouse-based screens for mutants in a group of plants containing about 2,900 insertions revealed about 31 dominant mutants, suggesting a dominant mutant frequency of about 1%. From the first batch of about 400 stable insertions screened in the greenhouse, four gain-in-function, dominant activation-tagged, morphological mutants were identified. A novel gain-in-function mutant called thread is described, in which the target gene belongs to the same family as the YUCCA flavin-mono-oxygenase that was identified by T-DNA activation tagging. The high frequency of identified gain-in-function mutants in the population suggests that the En-I system described here is an efficient strategy to saturate plant genomes with activation tag inserts. Because only a small number of primary transformants are required to generate an activation tag population, the En-I system appears to be an attractive alternative to study plant species where the present transformation methods have low efficiencies.
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193
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Azachi M, Sadka A, Fisher M, Goldshlag P, Gokhman I, Zamir A. Salt induction of fatty acid elongase and membrane lipid modifications in the extreme halotolerant alga Dunaliella salina. PLANT PHYSIOLOGY 2002; 129:1320-9. [PMID: 12114585 PMCID: PMC166525 DOI: 10.1104/pp.001909] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2001] [Revised: 01/31/2002] [Accepted: 03/13/2002] [Indexed: 05/20/2023]
Abstract
In studies of the outstanding salt tolerance of the unicellular green alga Dunaliella salina, we isolated a cDNA for a salt-inducible mRNA encoding a protein homologous to plant beta-ketoacyl-coenzyme A (CoA) synthases (Kcs). These microsomal enzymes catalyze the condensation of malonyl-CoA with acyl-CoA, the first and rate-limiting step in fatty acid elongation. Kcs activity, localized to a D. salina microsomal fraction, increased in cells transferred from 0.5 to 3.5 M NaCl, as did the level of the kcs mRNA. The function of the kcs gene product was directly demonstrated by the condensing activity exhibited by Escherichia coli cells expressing the kcs cDNA. The effect of salinity on kcs expression in D. salina suggested the possibility that salt adaptation entailed modifications in the fatty acid composition of algal membranes. Lipid analyses indicated that microsomes, but not plasma membranes or thylakoids, from cells grown in 3.5 M NaCl contained a considerably higher ratio of C18 (mostly unsaturated) to C16 (mostly saturated) fatty acids compared with cells grown in 0.5 M salt. Thus, the salt-inducible Kcs, jointly with fatty acid desaturases, may play a role in adapting intracellular membrane compartments to function in the high internal glycerol concentrations balancing the external osmotic pressure.
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Affiliation(s)
- Malkit Azachi
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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194
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Wang A, Xia Q, Xie W, Dumonceaux T, Zou J, Datla R, Selvaraj G. Male gametophyte development in bread wheat (Triticum aestivum L.): molecular, cellular, and biochemical analyses of a sporophytic contribution to pollen wall ontogeny. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 30:613-23. [PMID: 12061894 DOI: 10.1046/j.1365-313x.2002.01313.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Bread wheat (hexaploid AABBDD genome; 16 billion basepairs) is a genetically complex, self-pollinating plant with bisexual flowers that produce short-lived pollen. Very little is known about the molecular biology of its gametophyte development despite a longstanding interest in hybrid seeds. We present here a comprehensive characterization of three apparently homeologous genes (TAA1a, TAA1b and TAA1c) and demonstrate their anther-specific biochemical function. These eight-exon genes, found at only one copy per haploid complement in this large genome, express specifically within the sporophytic tapetum cells. The presence of TAA1 mRNA and protein was evident only at specific stages of pollen development as the microspore wall thickened during the progression of free microspores into vacuolated-microspores. This temporal regulation matched the assembly of wall-impregnated sporopollenin, a phenylpropanoid-lipid polymer containing very long chain fatty alcohols (VLCFAlc), described in the literature. Our results establish that sporophytic genes contribute to the production of fatty alcohols: Transgenic expression of TAA1 afforded production of long/VLCFAlc in tobacco seeds (18 : 1; 20 : 1; 22 : 1; 24 : 0; 26 : 0) and in Escherichia coli (14 : 0; 16 : 0; 18 : 1), suggesting biochemical versatility of TAA1 with respect to cellular milieu and substrate spectrum. Pollen walls additionally contain fatty alcohols in the form of wax esters and other lipids, and some of these lipids are known to play a role in the highly specific sexual interactions at the pollen-pistil interface. This study provides a handle to study these and to manipulate pollen traits, and, furthermore, to understand the molecular biology of fatty alcohol metabolism in general.
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Affiliation(s)
- Aiming Wang
- Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9
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195
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Affiliation(s)
- Christiane Nawrath
- Department of Biology, Unit of Plant Biology, University of Fribourg, Pérolles, Switzerland; phone:0041-(0)26-300 88 38; fax: 0041-(0)26-300 97 40;
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196
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Tanaka H, Watanabe M, Watanabe D, Tanaka T, Machida C, Machida Y. ACR4, a putative receptor kinase gene of Arabidopsis thaliana, that is expressed in the outer cell layers of embryos and plants, is involved in proper embryogenesis. PLANT & CELL PHYSIOLOGY 2002; 43:419-28. [PMID: 11978870 DOI: 10.1093/pcp/pcf052] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The surfaces of higher plants are characterized by epidermis, which usually consists of a single layer of cells. The epidermis is derived from the outer cell layer of the embryo or protoderm, which arises as a result of periclinal cell division. After seed germination, most of the epidermal cells of the aerial parts of plants are derived from the outer cell layer of the shoot apical meristem (the L1 layer). Thus, knowledge of how the protoderm and/or L1 layer is established is fundamental to understanding the morphogenesis of higher plants. Here, we report the isolation of a gene encoding an Arabidopsis homologue (ACR4) of the maize putative receptor kinase CRINKLY4 (CR4), which is involved in epidermal differentiation. The domain organization of the predicted amino acid sequence of ACR4 is essentially identical to that of CR4. ACR4-GFP fusion protein localized to the cell surface when expressed in tobacco cell (BY-2) culture. ACR4 transcripts were detected in all the organs of the Arabidopsis plant. In developing embryos and shoot apices, ACR4 transcripts accumulated in protoderm and epidermis at relatively higher levels than in the inner tissues. Over-expression of antisense ACR4 in Arabidopsis plants resulted in malformation of embryos to varying degrees. These results suggest that ACR4 is, at a minimum, involved in the normal morphogenesis of embryos, most likely through properly differentiating protoderm cells.
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MESH Headings
- Amino Acid Sequence
- Arabidopsis/enzymology
- Arabidopsis/genetics
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Gene Expression Regulation, Plant
- In Situ Hybridization
- Molecular Sequence Data
- Plant Epidermis/enzymology
- Plant Epidermis/genetics
- Plant Stems/enzymology
- Plant Stems/genetics
- Plants, Genetically Modified
- Protein Serine-Threonine Kinases
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor Protein-Tyrosine Kinases/genetics
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Seeds/enzymology
- Seeds/genetics
- Seeds/growth & development
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Zea mays/genetics
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Affiliation(s)
- Hirokazu Tanaka
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku 464-8602 Japan
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197
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Tanaka H, Onouchi H, Kondo M, Hara-Nishimura I, Nishimura M, Machida C, Machida Y. A subtilisin-like serine protease is required for epidermal surface formation inArabidopsisembryos and juvenile plants. Development 2001; 128:4681-9. [PMID: 11731449 DOI: 10.1242/dev.128.23.4681] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The surfaces of land plants are covered with a cuticle that is essential for retention of water. Epidermal surfaces of Arabidopsis thaliana embryos and juvenile plants that were homozygous for abnormal leaf shape1 (ale1) mutations were defective, resulting in excessive water loss and organ fusion in young plants. In ale1 embryos, the cuticle was rudimentary and remnants of the endosperm remained attached to developing embryos. Juvenile plants had a similar abnormal cuticle. The ALE1 gene was isolated using a transposon-tagged allele ale1-1. The predicted ALE1 amino acid sequence was homologous to those of subtilisin-like serine proteases. The ALE1 gene was found to be expressed within certain endosperm cells adjacent to the embryo and within the young embryo. Expression was not detected after germination. Our results suggest that the putative protease ALE1 affects the formation of cuticle on embryos and juvenile plants and that an appropriate cuticle is required for separation of the endosperm from the embryo and for prevention of organ fusion.
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Affiliation(s)
- H Tanaka
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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198
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Baroux C, Blanvillain R, Moore IR, Gallois P. Transactivation of BARNASE under the AtLTP1 promoter affects the basal pole of the embryo and shoot development of the adult plant in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 28:503-515. [PMID: 11849591 DOI: 10.1046/j.1365-313x.2001.01174.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Genetically controlled expression of a toxin provides a tool to remove a specific structure and consequently study its role during a developmental process. The availability of many tissue-specific promoters is a good argument for the development of such a strategy in plants. We have developed a conditional system for targeted toxin expression and demonstrated its use for generating embryo phenotypes that can bring valuable information about signalling during embryogenesis. The BARNASE gene was expressed in the Arabidopsis embryo under the control of two promoters, one from the cyclin AtCYCB1 gene and one from the AtLTP1 gene (Lipid Transfer Protein 1). One-hundred percent seed abortion was obtained with the cyclin promoter. Surprisingly however, the embryos displayed a range of lethal phenotypes instead of a single arrested stage as expected from this promoter. We also show that BARNASE expression under the control of the AtLTP1 promoter affects the basal pole of the globular embryo. Together with reporter expression studies, this result suggests a role of the epidermis in controlling the development of the lower tier of the embryo. This defect was not embryo-lethal and we show that the seedlings displayed a severe shoot phenotype correlated to epidermal defects. Therefore, the epidermis does not play an active role during organogenesis in seedlings but is important for the postgermination development of a viable plant.
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Affiliation(s)
- C Baroux
- Laboratoire Génome et Développement des Plantes, CNRS-UMR 5096, 52 avenue de Villeneuve, 66 000 Perpignan, France
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Wellesen K, Durst F, Pinot F, Benveniste I, Nettesheim K, Wisman E, Steiner-Lange S, Saedler H, Yephremov A. Functional analysis of the LACERATA gene of Arabidopsis provides evidence for different roles of fatty acid omega -hydroxylation in development. Proc Natl Acad Sci U S A 2001; 98:9694-9. [PMID: 11493698 PMCID: PMC55514 DOI: 10.1073/pnas.171285998] [Citation(s) in RCA: 205] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We describe lacerata (lcr) mutants of Arabidopsis, which display various developmental abnormalities, including postgenital organ fusions, and report cloning of the LCR gene by using the maize transposon Enhancer/Suppressor-mutator (En/Spm). The pleiotropic mutant phenotype could be rescued by genetic complementation of lcr mutants with the wild-type LCR gene. The LCR gene encodes a cytochrome P450 monooxygenase, CYP86A8, which catalyzes omega-hydroxylation of fatty acids ranging from C12 to C18:1, as demonstrated by expression of the gene in yeast. Although palmitic and oleic acids were efficient substrates for LCR, 9,10-epoxystearate was not metabolized. Taken together with previous studies, our findings indicate that LCR-dependent omega-hydroxylation of fatty acids could be implicated in the biosynthesis of cutin in the epidermis and in preventing postgenital organ fusions. Strikingly, the same pathway seems to control trichome differentiation, the establishment of apical dominance, and senescence in plants.
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Affiliation(s)
- K Wellesen
- Max-Planck-Institut für Züchtungsforschung, Cologne, Germany
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Johnson SA, McCormick S. Pollen germinates precociously in the anthers of raring-to-go, an Arabidopsis gametophytic mutant. PLANT PHYSIOLOGY 2001; 126:685-95. [PMID: 11402197 PMCID: PMC111159 DOI: 10.1104/pp.126.2.685] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2001] [Revised: 03/20/2001] [Accepted: 04/01/2001] [Indexed: 05/17/2023]
Abstract
Pollen hydration is usually tightly regulated and occurs in vivo only when desiccated pollen grains acquire water from the female, thus enabling pollen tube growth. Pollen tubes are easily visualized by staining with decolorized aniline blue, a stain specific for callose. We identified a mutant, raring-to-go, in which pollen grains stained for callose before anther dehiscence. When raring-to-go plants are transferred to high humidity, pollen tubes dramatically elongate within the anther. As early as the bicellular stage, affected pollen grains in raring-to-go plants acquire or retain water within the anther, and precociously germinate. Thus, the requirement for contact with the female is circumvented. We used pollen tetrad analysis to show that raring-to-go is a gametophytic mutation, to our knowledge the first gametophytic mutation in Arabidopsis that affects early events in the pollination pathway. To aid in identifying raring-to-go alleles, we devised a new technique for screening pollen in bulk with decolorized aniline blue. We screened a new M(1) mutagenized population and identified several additional mutants with a raring-to-go-like phenotype, demonstrating the usefulness of this technique. Further, we isolated other mutants (gift-wrapped pollen, polka dot pollen, and emotionally fragile pollen) with unexpected patterns of callose staining. We suggest that raring-to-go and these other mutants may help dissect components of the pathway that regulates pollen hydration and pollen tube growth.
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Affiliation(s)
- S A Johnson
- Plant Gene Expression Center, United States Department of Agriculture/Agricultural Research Service, University of California-Berkeley, 800 Buchanan Street, Albany, California 94710, USA.
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