Characterization of the GPI-anchored lipid transfer proteins in the moss Physcomitrella patens

Genome-wide identification and evolutionary analysis of the AP2/EREBP, COX and LTP genes in Zea mays L. under drought stress

AP2 (APETALA2)/EREBP (ethylene-responsive element-binding protein), cytochrome c oxidase (COX) and nonspecific lipid transfer proteins (LTP) play important roles in the response to drought stress. This is the first study to identify the COX gene in Zea mays L. via genome-wide analysis. The qRT‒PCR results indicated that AP2/EREBP, COX and LTP were downregulated, with fold changes of 0.84, 0.53 and 0.31, respectively, after 12 h of drought stress. Genome-wide analysis identified 78 AP2/EREBP, 6 COX and 10 LTP genes in Z. mays L. Domain analysis confirmed the presence of the AP2 domain, Cyt_c_Oxidase_Vb domain and nsLTP1 in the AP2/EREBP, COX and LTP proteins, respectively. The AP2/EREBP protein family (AP2) includes five different domain types: the AP2/ERF domain, the EREBP-like factor (EREBP), the ethylene responsive factor (ERF), the dehydration responsive element binding protein (DREB) and the SHN SHINE. Synteny analysis of the AP2/EREBP, COX and LTP genes revealed collinearity orthologous relationships in O. sativa, H. vulgare and A. thaliana. AP2/EREBP genes were found on the 10 chromosomes of Z. mays L. COX genes were found on chromosomes 1, 3, 4, 5, 7 and 8. LTP genes were found on chromosomes 1, 3, 6, 8, 9 and 10. In the present study, the Ka/Ks ratios of the AP2/EREBP paralogous pairs indicated that the AP2/EREBP genes were influenced primarily by purifying selection, which indicated that the AP2/EREBP genes received strong environmental pressure during evolution. The Ka/Ks ratios of the COX-3/COX-4 paralogous pairs indicate that the COX-3/COX-4 genes were influenced primarily by Darwinian selection (driving change). For the LTP genes, the Ka/Ks ratios of the LTP-1/LTP-10, LTP-5/LTP-3 and LTP-4/LTP-8 paralogous pairs indicate that these genes were influenced primarily by purifying selection, while the Ka/Ks ratios of the LTP-2/LTP-6 paralogous pairs indicate that these genes were influenced primarily by Darwinian selection. The duplication time of the AP2/EREBP paralogous gene pairs in Z. mays L. ranged from approximately 9.364 to 100.935 Mya. The duplication time of the COX-3/COX-4 paralogous gene pair was approximately 5.217 Mya. The duplication time of the LTP paralogous gene pairs ranged from approximately 19.064 to 96.477 Mya. The major focus of research is to identify the genes that are responsible for drought stress tolerance to improve maize for drought stress tolerance. The results of the present study will improve the understanding of the functions of the AP2/EREBP, COX and LTP genes in response to drought stress.

The non-specific lipid transfer protein McLTPII.9 of Mentha canadensis is involved in peltate glandular trichome density and volatile compound metabolism

Mentha canadensis L. is an important spice crop and medicinal herb with high economic value. The plant is covered with peltate glandular trichomes, which are responsible for the biosynthesis and secretion of volatile oils. Plant non-specific lipid transfer proteins (nsLTPs) belong to a complex multigenic family involved in various plant physiological processes. Here, we cloned and identified a non-specific lipid transfer protein gene (McLTPII.9) from M. canadensis, which may positively regulate peltate glandular trichome density and monoterpene metabolism. McLTPII.9 was expressed in most M. canadensis tissues. The GUS signal driven by the McLTPII.9 promoter in transgenic Nicotiana tabacum was observed in stems, leaves, and roots; it was also expressed in trichomes. McLTPII.9 was associated with the plasma membrane. Overexpression of McLTPII.9 in peppermint (Mentha piperita. L) significantly increased the peltate glandular trichome density and total volatile compound content compared with wild-type peppermint; it also altered the volatile oil composition. In McLTPII.9-overexpressing (OE) peppermint, the expression levels of several monoterpenoid synthase genes and glandular trichome development-related transcription factors-such as limonene synthase (LS), limonene-3-hydroxylase (L3OH), geranyl diphosphate synthase (GPPS), HD-ZIP3, and MIXTA-exhibited varying degrees of alteration. McLTPII.9 overexpression resulted in both a change in expression of genes for terpenoid biosynthetic pathways which corresponded with an altered terpenoid profile in OE plants. In addition, peltate glandular trichome density was altered in the OE plants as well as the expression of genes for transcription factors that were shown to be involved in trichome development in plants.

Functional conservation of an AP2/ERF transcription factor in cuticle formation suggests an important role in the terrestrialization of early land plants

The formation of a hydrophobic cuticle layer on aerial plant parts was a critical innovation for protection from the terrestrial environment during the evolution of land plants. However, little is known about the molecular mechanisms underlying cuticle biogenesis in early terrestrial plants. Here, we report an APETALA2/Ethylene Response Factor (AP2/ERF) transcriptional activator, PpWIN1, involved in cutin and cuticular wax biosynthesis in Physcomitrium patens and Arabidopsis. The transcript levels of PpWIN1 were 2.5-fold higher in gametophores than in the protonema, and increased by approximately 3- to 4.7-fold in the protonema and gametophores under salt and osmotic stresses. PpWIN1 harbouring transcriptional activation activity is localized in the nucleus of tobacco leaf epidermal cells. Δppwin1 knockout mutants displayed a permeable cuticle, increased water loss, and cutin- and wax-deficient phenotypes. In contrast, increased total cutin and wax loads, and decreased water loss rates were observed in PpWIN1-overexpressing Arabidopsis plants. The transcript levels of genes involved in cutin or wax biosynthesis were significantly up-regulated in PpWIN1-overexpressing Arabidopsis lines, indicating that PpWIN1 acts as a transcriptional activator in cuticle biosynthesis. This study suggests that Arabidopsis WIN1/SHN1 orthologs may be functionally conserved from early to vascular land plants.

Lipid transfer proteins involved in plant-pathogen interactions and their molecular mechanisms

Nonspecific lipid transfer proteins (LTPs) are small, cysteine-rich proteins that play numerous functional roles in plant growth and development, including cutin wax formation, pollen tube adhesion, cell expansion, seed development, germination, and adaptation to changing environmental conditions. LTPs contain eight conserved cysteine residues and a hydrophobic cavity that provides a wide variety of lipid-binding specificities. As members of the pathogenesis-related protein 14 family (PR14), many LTPs inhibit fungal or bacterial growth, and act as positive regulators in plant disease resistance. Over the past decade, these essential immunity-related roles of LTPs in plant immune processes have been documented in a growing body of literature. In this review, we summarize the roles of LTPs in plant-pathogen interactions, emphasizing the underlying molecular mechanisms in plant immune responses and specific LTP functions.

Genome-Wide Identification and Expression Analysis of nsLTP Gene Family in Rapeseed (Brassica napus) Reveals Their Critical Roles in Biotic and Abiotic Stress Responses

Non-specific lipid transfer proteins (nsLTPs) are small cysteine-rich basic proteins which play essential roles in plant growth, development and abiotic/biotic stress response. However, there is limited information about the nsLTP gene (BnLTP) family in rapeseed (Brassica napus). In this study, 283 BnLTP genes were identified in rapeseed, which were distributed randomly in 19 chromosomes of rapeseed. Phylogenetic analysis showed that BnLTP proteins were divided into seven groups. Exon/intron structure and MEME motifs both remained highly conserved in each BnLTP group. Segmental duplication and hybridization of rapeseed’s two sub-genomes mainly contributed to the expansion of the BnLTP gene family. Various potential cis-elements that respond to plant growth, development, biotic/abiotic stresses, and phytohormone signals existed in BnLTP gene promoters. Transcriptome analysis showed that BnLTP genes were expressed in various tissues/organs with different levels and were also involved in the response to heat, drought, NaCl, cold, IAA and ABA stresses, as well as the treatment of fungal pathogens (Sclerotinia sclerotiorum and Leptosphaeria maculans). The qRT-PCR assay validated the results of RNA-seq expression analysis of two top Sclerotinia-responsive BnLTP genes, BnLTP129 and BnLTP161. Moreover, batches of BnLTPs might be regulated by BnTT1 and BnbZIP67 to play roles in the development, metabolism or adaptability of the seed coat and embryo in rapeseed. This work provides an important basis for further functional study of the BnLTP genes in rapeseed quality improvement and stress resistance.

The Influence of Biomolecule Composition on Colloidal Beer Structure

Recent studies have revealed an interest in the composition of beer biomolecules as a colloidal system and their influence on the formation of beer taste. The purpose of this research was to establish biochemical interactions between the biomolecules of plant-based raw materials of beer in order to understand the overall structure of beer as a complex system of bound biomolecules. Generally accepted methods of analytical research in the field of brewing, biochemistry and proteomics were used to solve the research objectives. The studies allowed us to establish the relationship between the grain and plant-based raw materials used, as well as the processing technologies and biomolecular profiles of beer. The qualitative profile of the distribution of protein compounds as a framework for the formation of a colloidal system and the role of carbohydrate dextrins and phenol compounds are given. This article provides information about the presence of biogenic compounds in the structure of beer that positively affect the functioning of the body. A critical assessment of the influence of some parameters on the completeness of beer taste by biomolecules is given. Conclusion: the conducted analytical studies allowed us to confirm the hypothesis about the nitrogen structure of beer and the relationship of other biomolecules with protein substances, and to identify the main factors affecting the distribution of biomolecules by fractions.

Assessment of antimicrobial phytopeptides: lipid transfer protein and hevein-like peptide in the prospect of structure, function and allergenic effect

Background

Antimicrobial peptides (AMPs) are unique natural antibiotics that are crucial effectors of innate immune systems in almost all living organisms. Several different plant antimicrobial peptides have been identified and isolated, demonstrating a high level of protection against various types of bacteria, insects, nematodes and other microbes. Along with antimicrobial function, these peptides play a wide range of crucial function in plants, such as regulation of stomata, ion channel, heavy metals and membrane fluidity.

Main body

Antimicrobial peptides show a continuum of toxicity for a variety of plants and animals pathogenic microbes and even show cytotoxicity against cancer cells. Numerous studies have shown that transgenic plants have increased the expression of AMP-encoding genes in response to biotic and abiotic stresses, and plants that express transgenic AMP genes are more responsive to biotic, abiotic and other functions. In addition to being a molecule with protective properties, various allergic reactions are associated with some phytopeptides and proteins, in particular non-specific lipid transfer protein (nsLTP) and peptide-like hevein. Pru p3 from peach is the most clinically important allergen within the nsLTP family that cause real food allergies and also triggers extreme clinical reactions. Similarly, latex-fruit syndrome was primarily associated with well-studied latex allergen Hevein (Hev b8, Hev b6) and class I chitinases.

Short conclusions

Several findings have shown that, in the near future, transgenic plants based on AMPs against the verity of pathogenic fungi, bacteria and other abiotic stresses will be released without any adverse effects. Recent study reason that association of lipid with nsLTP enhances allergic sensitization and hevein-like domain of chitinase I essentially plays a role in cross-sensitivity of latex with different fruits and nuts. This review discusses the structures and various functions of lipid transfer protein and hevein-like peptide.

Effects of Salinity and Abscisic Acid on Lipid Transfer Protein Accumulation, Suberin Deposition and Hydraulic Conductance in Pea Roots

Lipid transfer proteins (LTPs) participate in many important physiological processes in plants, including adaptation to stressors, e.g., salinity. Here we address the mechanism of this protective action of LTPs by studying the interaction between LTPs and abscisic acid (ABA, a "stress" hormone) and their mutual participation in suberin deposition in root endodermis of salt-stressed pea plants. Using immunohistochemistry we show for the first time NaCl induced accumulation of LTPs and ABA in the cell walls of phloem paralleled by suberin deposition in the endoderm region of pea roots. Unlike LTPs which were found localized around phloem cells, ABA was also present within phloem cells. In addition, ABA treatment resulted in both LTP and ABA accumulation in phloem cells and promoted root suberization. These results suggested the importance of NaCl-induced accumulation of ABA in increasing the abundance of LTPs and of suberin. Using molecular modeling and fluorescence spectroscopy we confirmed the ability of different plant LTPs, including pea Ps-LTP1, to bind ABA. We therefore hypothesize an involvement of plant LTPs in ABA transport (unloading from phloem) as part of the salinity adaptation mechanism.

Tissue-specific expression of GhnsLTPs identified via GWAS sophisticatedly coordinates disease and insect resistance by regulating metabolic flux redirection in cotton

Cotton (Gossypium hirsutum) is constantly attacked by pathogens and insects. The most efficient control strategy is to develop resistant varieties using broad-spectrum gene resources. Several resistance loci harboured by superior varieties have been identified through genome-wide association studies. However, the key genes and/or loci have not been functionally identified. In this study, we identified a locus significantly associated with Verticillium wilt (VW) resistance, and within a 145.5-kb linkage disequilibrium, two non-specific lipid transfer protein genes (named GhnsLTPsA10) were highly expressed under Verticillium pathogen stress. The expression of GhnsLTPsA10 significantly increased in roots upon Verticillium dahliae stress but significantly decreased in leaves under insect attack. Furthermore, GhnsLTPsA10 played antagonistic roles in positively regulating VW and Fusarium wilt resistance and negatively mediating aphid and bollworm resistance in transgenic Arabidopsis and silenced cotton. By combining transcriptomic, histological and physiological analyses, we determined that GhnsLTPsA10-mediated phenylpropanoid metabolism further affected the balance of the downstream metabolic flux of flavonoid and lignin biosynthesis. The divergent expression of GhnsLTPsA10 in roots and leaves coordinated resistance of cotton against fungal pathogens and insects via the redirection of metabolic flux. In addition, GhnsLTPsA10 contributed to reactive oxygen species accumulation. Therefore, in this study, we elucidated the novel function of GhnsLTP and the molecular association between disease resistance and insect resistance, balanced by GhnsLTPsA10. This broadens our knowledge of the biological function of GhnsLTPsA10 in crops and provides a useful locus for genetic improvement of cotton.

Identification and functional analysis of the MdLTPG gene family in apple

Cuticular wax is synthesized from intracellular lipids that are exported by epidermal cells, and plant lipid transfer proteins (LTPs) play an important role in this process. The glycosylphosphatidylinositol (GPI)-anchored LTPs (LTPGs) are a large subgroup within the LTP family and function in lipid transport and wax formation. Although LTPG family members have been identified in several plant species, the LTPG gene family of apple (Malus domestica) remains uncharacterized. In this paper, we identified 26 potential LTPG genes by searching apple whole-genome annotation files using "GPI-anchored" and "lipid transferase" as keywords. Twenty of the 26 putative LTPG genes were confirmed as MdLTPG family members based on their subcellular localization predictions. The MdLTPGs were divided into four classes based on phylogenetic analysis and functional domain prediction. One member of each class was analyzed for subcellular localization, and all identified members were located on the plasma membrane. Most MdLTPG genes were induced by abiotic stress treatments such as low temperature, NaCl, and ABA. Finally, the MdLTPG17 protein was shown to interact with the lysine-rich arabinogalactan protein MdAGP18 to perform its function in wax transport during plant growth and development.

Genome-Wide Analysis of nsLTP Gene Family and Identification of SiLTPs Contributing to High Oil Accumulation in Sesame (Sesamum indicum L.)

The biosynthesis and storage of lipids in oil crop seeds involve many gene families, such as nonspecific lipid-transfer proteins (nsLTPs). nsLTPs are cysteine-rich small basic proteins essential for plant development and survival. However, in sesame, information related to nsLTPs was limited. Thus, the objectives of this study were to identify the Sesamum indicum nsLTPs (SiLTPs) and reveal their potential role in oil accumulation in sesame seeds. Genome-wide analysis revealed 52 SiLTPs, nonrandomly distributed on 10 chromosomes in the sesame variety Zhongzhi 13. Following recent classification methods, the SiLTPs were divided into nine types, among which types I and XI were the dominants. We found that the SiLTPs could interact with several transcription factors, including APETALA2 (AP2), DNA binding with one finger (Dof), etc. Transcriptome analysis showed a tissue-specific expression of some SiLTP genes. By integrating the SiLTPs expression profiles and the weighted gene co-expression network analysis (WGCNA) results of two contrasting oil content sesame varieties, we identified SiLTPI.23 and SiLTPI.28 as the candidate genes for high oil content in sesame seeds. The presumed functions of the candidate gene were validated through overexpression of SiLTPI.23 in Arabidopsis thaliana. These findings expand our knowledge on nsLTPs in sesame and provide resources for functional studies and genetic improvement of oil content in sesame seeds.

Cysteine-rich antimicrobial peptides from plants: The future of antimicrobial therapy

There has been a spurt in the spread of microbial resistance to antibiotics due to indiscriminate use of antimicrobial agents in human medicine, agriculture, and animal husbandry. It has been realized that conventional antibiotic therapy would be less effective in the coming decades and more emphasis should be given for the development of novel antiinfective therapies. Cysteine rich peptides (CRPs) are broad-spectrum antimicrobial agents that modulate the innate immune system of different life forms such as bacteria, protozoans, fungi, plants, insects, and animals. These are also expressed in several plant tissues in response to invasion by pathogens, and play a crucial role in the regulation of plant growth and development. The present work explores the importance of CRPs as potent antimicrobial agents, which can supplement and/or replace the conventional antibiotics. Different plant parts of diverse plant species showed the presence of antimicrobial peptides (AMPs), which had significant structural and functional diversity. The plant-derived AMPs exhibited potent activity toward a range of plant and animal pathogens, protozoans, insects, and even against cancer cells. The cysteine-rich AMPs have opened new avenues for the use of plants as biofactories for the production of antimicrobials and can be considered as promising antimicrobial drugs in biotherapeutics.

The lipid transfer protein OsLTPL159 is involved in cold tolerance at the early seedling stage in rice

Nonspecific lipid transfer proteins (nsLTPs) play critical roles in plant development and response to abiotic stresses. Here, we found that a rice lipid transfer protein, OsLTPL159, was associated with cold tolerance at the early seedling stage. Overexpression of an OsLTPL159^IL112 allele from the cold-tolerant introgression line IL112 in either the japonica variety Zhonghua17 (ZH17) or the indica variety Teqing background dramatically enhanced cold tolerance. In addition, down-regulation of the expression of OsLTPL159 in the japonica variety ZH17 by RNA interference (RNAi) significantly decreased cold tolerance. Further transcriptomic, physiological and histological analysis showed that the OsLTPL159^IL112 allele likely enhanced the cold tolerance of rice at the early seedling stage by decreasing the toxic effect of reactive oxygen species, enhancing cellulose deposition in the cell wall and promoting osmolyte accumulation, thereby maintaining the integrity of the chloroplasts. Notably, overexpression of another allele, OsLTPL159^GC2 , from the recipient parent Guichao 2 (GC2), an indica variety, did not improve cold tolerance, indicating that the variations in the OsLTPL159 coding region of GC2 might disrupt its function for cold tolerance. Further sequence comparison found that all 22 japonica varieties surveyed had an OsLTPL159 haplotype identical to IL112 and were more cold-tolerant than the surveyed indica varieties, implying that the variations in OsLTPL159 might be associated with differential cold tolerance of japonica and indica rice. Therefore, our findings suggest that the OsLTPL159 allele of japonica rice could be used to improve cold tolerance of indica rice through a molecular breeding strategy.

Occurrence of land-plant-specific glycerol-3-phosphate acyltransferases is essential for cuticle formation and gametophore development in Physcomitrella patens

During the evolution of land plants from aquatic to terrestrial environments, their aerial surfaces were surrounded by cuticle composed of cutin and cuticular waxes to protect them from environmental stresses. Glycerol-3-phosphate acyltransferase (GPAT) harboring bifunctional sn-2 acyltransferase/phosphatase activity produces 2-monoacylglycerol, a precursor for cutin synthesis. Here, we report that bifunctional sn-2 GPATs play roles in cuticle biosynthesis and gametophore development of Physcomitrella patens. Land plant-type cuticle was observed in gametophores but not in protonema. The expression of endoplasmic reticulum-localized PpGPATs was significantly upregulated in gametophores compared with protonema. Floral organ fusion and permeable cuticle phenotypes of Arabidopsis gpat6-2 petals were rescued to the wild type (WT) by the expression of PpGPAT2 or PpGPAT4. Disruption of PpGPAT2 and PpGPAT4 caused a significant reduction of total cutin loads, and a prominent decrease in the levels of palmitic and 10,16-dihydroxydecanoic acids, which are major cutin monomers in gametophores. Δppgpat2 mutants displayed growth retardation, delayed gametophore development, increased cuticular permeability, and reduced tolerance to drought, osmotic and salt stresses compared to the WT. Genome-wide analysis of genes encoding acyltransferase or phosphatase domains suggested that the occurrence of sn-2 GPATs with both domains may be a key event in cuticle biogenesis of land plants.

Cold tolerance response mechanisms revealed through comparative analysis of gene and protein expression in multiple rice genotypes

Due to its tropical origin and adaptation, rice is significantly impacted by cold stress, and consequently sustains large losses in growth and productivity. Currently, rice is the second most consumed cereal in the world and production losses caused by extreme temperature events in the context of "major climatic changes" can have major impacts on the world economy. We report here an analysis of rice genotypes in response to low-temperature stress, studied through physiological gas-exchange parameters, biochemical changes in photosynthetic pigments and antioxidants, and at the level of gene and protein expression, towards an understanding and identification of multiple low-temperature tolerance mechanisms. The first effects of cold stress were observed on photosynthesis among all genotypes. However, the tropical japonica genotypes Secano do Brazil and Cypress had a greater reduction in gas exchange parameters like photosynthesis and water use efficiency in comparison to the temperate japonica Nipponbare and M202 genotypes. The analysis of biochemical profiles showed that despite the impacts of low temperature on tolerant plants, they quickly adjusted to maintain their cellular homeostasis by an accumulation of antioxidants and osmolytes like phenolic compounds and proline. The cold tolerant and sensitive genotypes showed a clear difference in gene expression at the transcript level for OsGH3-2, OsSRO1a, OsZFP245, and OsTPP1, as well as for expression at the protein level for LRR-RLKs, bHLH, GLYI, and LTP1 proteins. This study exemplifies the cold tolerant features of the temperate japonica Nipponbare and M202 genotypes, as observed through the analysis of physiological and biochemical responses and the associated changes in gene and protein expression patterns. The genes and proteins showing differential expression response are notable candidates towards understanding the biological pathways affected in rice and for engineering cold tolerance, to generate cultivars capable of maintaining growth, development, and reproduction under cold stress. We also propose that the mechanisms of action of the genes analyzed are associated with the tolerance response.

Purification and Characterization of a Nonspecific Lipid Transfer Protein 1 (nsLTP1) from Ajwain (Trachyspermum ammi) Seeds

Ajwain (Trachyspermum ammi) belongs to the family Umbelliferae, is commonly used in traditional, and folk medicine due to its carminative, stimulant, antiseptic, diuretic, antihypertensive, and hepatoprotective activities. Non-specific lipid transfer proteins (nsLTPs) reported from various plants are known to be involved in transferring lipids between membranes and in plants defense response. Here, we describe the complete primary structure of a monomeric non-specific lipid transfer protein 1 (nsLTP1), with molecular weight of 9.66 kDa, from ajwain seeds. The nsLTP1 has been purified by combination of chromatographic techniques, and further characterized by mass spectrometry, and Edman degradation. The ajwain nsLTP1 is comprised of 91 amino acids, with eight conserved cysteine residues. The amino acid sequence based predicted three dimensional (3D) structure is composed of four α-helices stabilized by four disulfide bonds, and a long C-terminal tail. The predicted model was verified by using different computational tools; i.e. ERRAT, verify 3D web server, and PROCHECK. The docking of ajwain nsLTP1 with ligands; myristic acid (MYR), and oleic acid (OLE) was performed, and molecular dynamics (MD) simulation was used to validate the docking results. The findings suggested that amino acids; Leu11, Leu12, Ala55, Ala56, Val15, Tyr59, and Leu62 are pivotal for the binding of lipid molecules with ajwain nsLTP1.

Impact of lipid binding on the tertiary structure and allergenic potential of Jug r 3, the non-specific lipid transfer protein from walnut

Plant non-specific lipid transfer proteins type 1 (nsLTP1) are small basic proteins with a hydrophobic cavity able to host a number of different ligands: i.e. fatty acids, fatty acyl-CoA, phospholipids, glycolipids, and hydroxylated fatty acids. However, ligand binding specificity differs among nsLTPs. Within this protein family, Jug r 3 from walnut has been identified as a major allergen. So far, data on the structural characterization of Jug r 3 and its lipid binding capacity are lacking. We report the results from a fluorescence-based ligand-binding assay and ligand-based NMR experiments, to study the binding interactions between Jug r 3 and the 18-carbon monounsaturated oleic acid. Furthermore, protein-based NMR experiments were employed to detect the oleate binding site of Jug r 3. The NMR data were used to dock the oleate molecule into the structural model of Jug r 3. Finally, the impact of the interaction on the allergenic potential of Jug r 3 was investigated by IgE ELISA with 6 sera from walnut allergic patients. Our data corroborate the hypothesis of direct impact of food-derived matrix on the IgE reactivity of nsLTPs.

Plant glycosylphosphatidylinositol anchored proteins at the plasma membrane-cell wall nexus

Approximately 1% of plant proteins are predicted to be post-translationally modified with a glycosylphosphatidylinositol (GPI) anchor that tethers the polypeptide to the outer leaflet of the plasma membrane. Whereas the synthesis and structure of GPI anchors is largely conserved across eukaryotes, the repertoire of functional domains present in the GPI-anchored proteome has diverged substantially. In plants, this includes a large fraction of the GPI-anchored proteome being further modified with plant-specific arabinogalactan (AG) O-glycans. The importance of the GPI-anchored proteome to plant development is underscored by the fact that GPI biosynthetic null mutants exhibit embryo lethality. Mutations in genes encoding specific GPI-anchored proteins (GAPs) further supports their contribution to diverse biological processes, occurring at the interface of the plasma membrane and cell wall, including signaling, cell wall metabolism, cell wall polymer cross-linking, and plasmodesmatal transport. Here, we review the literature concerning plant GPI-anchored proteins, in the context of their potential to act as molecular hubs that mediate interactions between the plasma membrane and the cell wall, and their potential to transduce the signal into the protoplast and, thereby, activate signal transduction pathways.

Plant lipid transfer proteins: are we finally closing in on the roles of these enigmatic proteins?

The nonspecific lipid transfer proteins (LTPs) are small compact proteins folded around a tunnel-like hydrophobic cavity, making them suitable for lipid binding and transport. LTPs are encoded by large gene families in all land plants, but they have not been identified in algae or any other organisms. Thus, LTPs are considered key proteins for plant survival on and colonization of land. LTPs are abundantly expressed in most plant tissues, both above and below ground. They are usually localized to extracellular spaces outside the plasma membrane. Although the in vivo functions of LTPs remain unclear, accumulating evidence suggests a role for LTPs in the transfer and deposition of monomers required for assembly of the waterproof lipid barriers, such as cutin and cuticular wax, suberin, and sporopollenin, formed on many plant surfaces. Some LTPs may be involved in other processes, such as signaling during pathogen attacks. Here, we present the current status of LTP research with a focus on the role of these proteins in lipid barrier deposition and cell expansion. We suggest that LTPs facilitate extracellular transfer of barrier materials and adhesion between barriers and extracellular materials. A growing body of research may uncover the true role of LTPs in plants.

Deciphering the Evolution and Development of the Cuticle by Studying Lipid Transfer Proteins in Mosses and Liverworts

When plants conquered land, they developed specialized organs, tissues, and cells in order to survive in this new and harsh terrestrial environment. New cell polymers such as the hydrophobic lipid-based polyesters cutin, suberin, and sporopollenin were also developed for protection against water loss, radiation, and other potentially harmful abiotic factors. Cutin and waxes are the main components of the cuticle, which is the waterproof layer covering the epidermis of many aerial organs of land plants. Although the in vivo functions of the group of lipid binding proteins known as lipid transfer proteins (LTPs) are still rather unclear, there is accumulating evidence suggesting a role for LTPs in the transfer and deposition of monomers required for cuticle assembly. In this review, we first present an overview of the data connecting LTPs with cuticle synthesis. Furthermore, we propose liverworts and mosses as attractive model systems for revealing the specific function and activity of LTPs in the biosynthesis and evolution of the plant cuticle.

Rice No Pollen 1 (NP1) is required for anther cuticle formation and pollen exine patterning

Angiosperm male reproductive organs (anthers and pollen grains) have complex and interesting morphological features, but mechanisms that underlie their patterning are poorly understood. Here we report the isolation and characterization of a male sterile mutant of No Pollen 1 (NP1) in rice (Oryza sativa). The np1-4 mutant exhibited smaller anthers with a smooth cuticle surface, abnormal Ubisch bodies, and aborted pollen grains covered with irregular exine. Wild-type exine has two continuous layers; but np1-4 exine showed a discontinuous structure with large granules of varying size. Chemical analysis revealed reduction in most of the cutin monomers in np1-4 anthers, and less cuticular wax. Map-based cloning suggested that NP1 encodes a putative glucose-methanol-choline oxidoreductase; and expression analyses found NP1 preferentially expressed in the tapetal layer from stage 8 to stage 10 of anther development. Additionally, the expression of several genes involved in biosynthesis and in the transport of lipid monomers of sporopollenin and cutin was decreased in np1-4 mutant anthers. Taken together, these observations suggest that NP1 is required for anther cuticle formation, and for patterning of Ubisch bodies and the exine. We propose that products of NP1 are likely important metabolites in the development of Ubisch bodies and pollen exine, necessary for polymerization, assembly, or both.

Lipid transfer proteins: classification, nomenclature, structure, and function

The non-specific lipid transfer proteins (LTPs) constitute a large protein family found in all land plants. They are small proteins characterized by a tunnel-like hydrophobic cavity, which makes them suitable for binding and transporting various lipids. The LTPs are abundantly expressed in most tissues. In general, they are synthesized with an N-terminal signal peptide that localizes the protein to spaces exterior to the plasma membrane. The in vivo functions of LTPs are still disputed, although evidence has accumulated for a role in the synthesis of lipid barrier polymers, such as cuticular waxes, suberin, and sporopollenin. There are also reports suggesting that LTPs are involved in signaling during pathogen attacks. LTPs are considered as key proteins for the plant's survival and colonization of land. In this review, we aim to present an overview of the current status of LTP research and also to discuss potential future applications of these proteins. We update the knowledge on 3D structures and lipid binding and review the most recent data from functional investigations, such as from knockout or overexpressing experiments. We also propose and argument for a novel system for the classification and naming of the LTPs.

A Non-specific Setaria italica Lipid Transfer Protein Gene Plays a Critical Role under Abiotic Stress

Lipid transfer proteins (LTPs) are a class of cysteine-rich soluble proteins having small molecular weights. LTPs participate in flower and seed development, cuticular wax deposition, also play important roles in pathogen and abiotic stress responses. A non-specific LTP gene (SiLTP) was isolated from a foxtail millet (Setaria italica) suppression subtractive hybridization library enriched for differentially expressed genes after abiotic stress treatments. A semi-quantitative reverse transcriptase PCR analysis showed that SiLTP was expressed in all foxtail millet tissues. Additionally, the SiLTP promoter drove GUS expression in root tips, stems, leaves, flowers, and siliques of transgenic Arabidopsis. Quantitative real-time PCR indicated that the SiLTP expression was induced by NaCl, polyethylene glycol, and abscisic acid (ABA). SiLTP was localized in the cytoplasm of tobacco leaf epidermal cells and maize protoplasts. The ectopic expression of SiLTP in tobacco resulted in higher levels of salt and drought tolerance than in the wild type (WT). To further assess the function of SiLTP, SiLTP overexpression (OE) and RNA interference (RNAi)-based transgenic foxtail millet were obtained. SiLTP-OE lines performed better under salt and drought stresses compared with WT plants. In contrast, the RNAi lines were much more sensitive to salt and drought compared than WT. Electrophoretic mobility shift assays and yeast one-hybrids indicated that the transcription factor ABA-responsive DRE-binding protein (SiARDP) could bind to the dehydration-responsive element of SiLTP promoter in vitro and in vivo, respectively. Moreover, the SiLTP expression levels were higher in SiARDP-OE plants compared than the WT. These results confirmed that SiLTP plays important roles in improving salt and drought stress tolerance of foxtail millet, and may partly be upregulated by SiARDP. SiLTP may provide an effective genetic resource for molecular breeding in crops to enhance salt and drought tolerance levels.

The Transcriptomic Response of Arabidopsis thaliana to Zinc Oxide: A Comparison of the Impact of Nanoparticle, Bulk, and Ionic Zinc

The impact of nanosize was evaluated by comparing of the transcriptomic response of Arabidopsis thaliana roots to ZnO nanoparticles (nZnO), bulk ZnO, and ionic Zn(2+). Microarray analyses revealed 416 up- and 961 down-regulated transcripts (expression difference >2-fold, p [FDR] < 0.01) after a seven-day treatment with nZnO (average particle size 20 nm, concentration 4 mg L(-1)). Exposure to bulk ZnO resulted in 816 up- and 2179 down-regulated transcripts. The most dramatic changes (1711 transcripts up- and 3242 down-regulated) were caused by the presence of ionic Zn(2+) (applied as ZnSO4.7H20 at a concentration of 14.14 mg L(-1), corresponding to the amount of Zn contained in 4 mg L(-1) ZnO). Genes involved in stress response (e.g., to salt, osmotic stress or water deprivation) were the most relatively abundant group of gene transcripts up-regulated by all three Zn treatments while genes involved in cell organization and biogenesis (e.g., tubulins, arabinogalactan proteins) and DNA or RNA metabolism (e.g., histones) were the most relatively abundant groups of down-regulated transcripts. The similarity of the transcription profiles and the increasing number of changed transcripts correlating with the increased concentration of Zn(2+) in cultivation medium indicated that released Zn(2+) may substantially contribute to the toxic effect of nZnO because particle size has not demonstrated a decisive role.

Non-specific lipid transfer proteins in plants: presenting new advances and an integrated functional analysis

Plant non-specific lipid-transfer proteins (nsLTPs) are small, basic proteins present in abundance in higher plants. They are involved in key processes of plant cytology, such as the stablization of membranes, cell wall organization, and signal transduction. nsLTPs are also known to play important roles in resistance to biotic and abiotic stress, and in plant growth and development, such as sexual reproduction, seed development and germination. The structures of plant nsLTPs contain an eight-cysteine residue conserved motif, linked by four disulfide bonds, and an internal hydrophobic cavity, which comprises the lipid-binding site. This structure endows stability and increases the ability to bind and/or carry hydrophobic molecules. There is growing interest in nsLTPs, due to their critical roles, resulting in the need for a comprehensive review of their form and function. Relevant topics include: nsLTP structure and biochemical features, their classification, identification, and characterization across species, sub-cellular localization, lipid binding and transfer ability, expression profiling, functionality, and evolution. We present advances, as well as limitations and trends, relating to the different topics of the nsLTP gene family. This review collates a large body of research pertaining to the role of nsLTPs across the plant kingdom, which has been integrated as an in depth functional analysis of this group of proteins as a whole, and their activities across multiple biochemical pathways, based on a large number of reports. This review will enhance our understanding of nsLTP activity in planta, prompting further work and insights into the roles of this multifaceted protein family in plants.