Isolation and characterization of a cDNA clone encoding a putative white spruce glycine-rich RNA binding protein

Protein profile of cotyledon, tegument, and embryonic axis of mature acorns from a non-orthodox plant species: Quercus ilex

Contrary to the orthodox seeds, recalcitrant Holm oak seeds possess the enzymatic machinery to start germination during the maturation phase. The protein profile of the different parts, mature seeds, of the Holm oak, a non-orthodox plant species, has been characterized using one- and two-dimensional gel electrophoresis coupled to matrix-assisted laser desorption ionization-time of flight mass spectrometry. Protein content and profiles of the three seed tissues (cotyledon, embryonic axis and tegument) were quite different. The embryonic axis showed 4-fold and 20-fold higher protein content than the cotyledon and the tegument, respectively. Two hundred and twenty-six variable proteins among the three seed parts were identified, being classified according to their function into eight main groups. The cotyledon presented the highest number of metabolic and storage proteins (89% of them are legumin) compared to the embryonic axis and tegument. The embryonic axis had the highest number of the species within the protein fate group. The tegument presented the largest number of the defense-/stress-related and cytoskeleton proteins. This distribution is in good agreement with the biological role of the tissues. The study of the seed tissue proteome demonstrated a compartmentalization of pathways and a division of metabolic tasks between embryonic axis, cotyledon and tegument. This compartmentalization uncovered in our study should provide a starting point for understanding, at the molecular level, the particularities of the recalcitrant seeds.

Molecular cloning, characterization, and stress-responsive expression of genes encoding glycine-rich RNA-binding proteins in Camelina sativa L

Camelina sativa L. is an oil-seed crop that has potential for biofuel applications. Although the importance of C. sativa as a biofuel crop has increased in recent years, reports demonstrating the stress responsiveness of C. sativa and characterizing the genes involved in stress response of C. sativa have never been published. Here, we isolated and characterized three genes encoding glycine-rich RNA-binding proteins (GRPs) from camelina: CsGRP2a, CsGRP2b, and CsGRP2c. The three CsGRP2 proteins were very similar in amino acid sequence and contained a well-conserved RNA-recognition motif at the N-terminal region and glycine-rich domain at the C-terminal region. To understand the functional roles of CsGRP2s under stress conditions, we investigated the expression patterns of CsGRP2s under various environmental stress conditions. The expressions of the three CsGRP2s were highly up-regulated under cold stress. The expression of CsGRP2a was up-regulated under salt or dehydration stress, whereas the transcript levels of CsGRP2b and CsGRP2c were decreased under salt or dehydration stress conditions. The three CsGRP2s had the ability to complement cold-sensitive Escherichia coli mutants at low temperatures and harbored transcription anti-termination and nucleic acid-melting activities, indicating that the CsGRP2s possess RNA chaperone activity. The CsGRP2a protein was localized to both the nucleus and the cytoplasm. Expression of CsGRP2a in cold-sensitive Arabidopsis grp7 mutant plants resulted in decreased electrolyte leakage at freezing temperatures. Collectively, these results suggest that the stress-responsive CsGRP2s play a role as an RNA chaperone during the stress adaptation process in camelina.

Molecular characterization and expression analysis of a glycine-rich RNA-binding protein gene from Malus hupehensis Rehd

Members of the plant glycine-rich RNA-binding protein (GR-RBP) family play diverse roles in regulating RNA metabolism for various cellular processes. To understand better their function at the molecular level in stress responses, we cloned a GR-RBP gene, MhGR-RBP1, from Malus hupehensis. Its full-length cDNA is 558 bp long, with a 495-bp open reading frame, and it encodes 164 amino acids. The deduced amino acid sequence contains an RNA-recognition motif (RRM) at the amino terminal and a glycine-rich domain at the carboxyl terminal; these are highly homologous with those from other plant species. Multiple alignment and phylogenetic analyses show that the deduced protein is a novel member of the plant GR-RBP family. To characterize this gene, we also applied a model for predicting its homology of protein structure with other species. Both organ-specific and stress-related expression were detected by quantitative real-time PCR and semi-quantitative RT-PCR, indicating that MhGR-RBP1 is expressed abundantly in young leaves but weakly in roots and shoots. Transcript levels in the leaves were increased markedly by drought, hydrogen peroxide (H(2)O(2)), and mechanical wounding, slightly by salt stress. Furthermore, the transcript is initially up- and down-regulated rapidly within 24 h of abscisic acid (ABA) treatment. After 24 h of ABA and jasmonic acid (JA) treatments with different concentrations, the transcript levels of MhGR-RBP1 were significantly repressed. These results suggest that MhGR-RBP1 may be involved in the responses to abiotic stresses, H(2)O(2), ABA, or JA.

Proteomic identification of putative plasmodesmatal proteins from Chara corallina

Plasmodesmata are channels that bridge the cell walls of plant cells, allowing regulated transport of molecules between neighbouring cells. We have used a proteomic strategy to identify putative plasmodesmata-associated proteins in the giant-celled green alga Chara corallina. Proteins were extracted from the plasmodesmata-rich nodal complexes and the middle of the long internodal cells, which do not contain plasmodesmata. Comparison of protein spot patterns generated by two-dimensional gel electrophoresis of both the soluble and cell wall fractions from the two cell types was done. Fifty-eight spots that were common to the nodal and internodal soluble fractions were analysed by matrix assisted laser desorption/ionisation-time of flight mass spectrometry, and peptide mass fingerprint data were used to search the database. Matches were made to four of these spots, in each case to housekeeping proteins. Further, a number of nodal specific spots were identified, 11 from the soluble fraction and nine from the wall fraction. These spots were excised from the gels and analysed by liquid chromatography tandem mass spectrometry to obtain peptide sequence. Database searches suggest that these spots include homologues to previously identified plasmodesmata-associated proteins cp-wap13 and heat shock cognate 70, as well as RNA-binding proteins, eukaryotic initiation factor 4A and a beta-1,3-glucanase. Several spots remained unidentified providing exciting new candidate plasmodesmata-associated proteins.

Anatomical and chemical defenses of conifer bark against bark beetles and other pests

Conifers are long-lived organisms, and part of their success is due to their potent defense mechanisms. This review focuses on bark defenses, a front line against organisms trying to reach the nutrient-rich phloem. A major breach of the bark can lead to tree death, as evidenced by the millions of trees killed every year by specialized bark-invading insects. Different defense strategies have arisen in conifer lineages, but the general strategy is one of overlapping constitutive mechanical and chemical defenses overlaid with the capacity to up-regulate additional defenses. The defense strategy incorporates a graded response from 'repel', through 'defend' and 'kill', to 'compartmentalize', depending upon the advance of the invading organism. Using a combination of toxic and polymer chemistry, anatomical structures and their placement, and inducible defenses, conifers have evolved bark defense mechanisms that work against a variety of pests. However, these can be overcome by strategies including aggregation pheromones of bark beetles and introduction of virulent phytopathogens. The defense structures and chemicals in conifer bark are reviewed and questions about their coevolution with bark beetles are discussed.

Cloning and expression analysis of a water stress-induced gene from Brassica oleracea

Plant growth and productivity are greatly affected by water stress, such as drought and salinity. Here we report on the cloning and expression analysis of a water stress-induced gene from Brassica oleracea (designated as BoWS, GenBank accession number AY571333) by rapid amplification of cDNA ends (RACE). The full-length cDNA of BoWS consisted of 594 bp and contained a 285 bp open reading frame (ORF) encoding a 95-amino-acid protein. The deduced protein had a calculated molecular mass of 10.53 kDa and an isoelectric point of 6.93. The sequence similarity and comparative analysis showed that BoWS was 84% identical to Arabidopsis thaliana putative water stress-induced protein (GenBank accession number AAM67282). Southern blot analysis indicated that BoWS was a low-copy gene. Northern blot analysis revealed that the expression of BoWS was upregulated by abscisic acid (ABA), mannitol, NaCl, drought, salicylic acid (SA) and hydrogen peroxide (H(2)O(2)). Our results indicate that BoWS is extremely related to the water-deficit stress in B. oleracea.

Osmotic stress of salmon stimulates upregulation of a cold inducible RNA binding protein (CIRP) similar to that of mammals and amphibians

Salmon are subjected to hyperosmotic stress during transition from freshwater to the marine environment. A variety of mechanisms have evolved to allow movement of the animal from a hydrating to a dehydrating environment. Using differential assay of mRNA expression, a 1.3 kb transcript was found to be upregulated in branchial lamellae of salmon exposed to hyperosmotic conditions. The transcript contains an open reading frame of 618 nt coding for a 205 amino acid protein with a molecular mass of 21.5 kDa. The putative protein, dubbed salmon glycine-rich RNA binding protein (SGRP), possesses a high degree of identity (>70%) with the cold inducible RNA binding proteins (CIRP) of mammals and amphibians and contains the canonical features of these proteins including a single RNA recognition motif (RRM), high glycine content and conserved flanking motifs. SGRP mRNA was observed to increase in response to hyperosmotic stress of branchial tissue with maximum levels of expression after 48 h of exposure. Transcript also was observed in liver, kidney and heart but was not upregulated significantly by osmotic stress in these tissues. Exposure of isolated lamellae to heat stress and sodium arsenite, known inducers of hsps, did not stimulate accumulation of SGRP transcript. Similarly, inhibition of protein synthesis with cycloheximide and the MAPK and MEK signal transduction pathways with SB202190 and PD98059 failed to alter expression of the gene. Of significance was the absence of an increase in expression of SGRP in response to cold stress (DeltaT = 5 and 12 degrees C for 12 and 24 h). The findings of this research suggest that ectothermic salmon inhabiting boreal waters possess a protein analogous to the CIRPs currently identified in mammals and amphibians. In contrast to the function of CIRPs, SGRP appears to have a more prominent role in adaptation to hyperosmotic conditions rather than cold stress.

A cDNA encoding a cold-induced glycine-rich RNA binding protein from Prunus avium expressed in embryonic axes

A cDNA clone encoding a presumed full-length glycine-rich ribonucleic acid (RNA) binding protein was isolated from a lambda-ZAP Express cDNA library generated from primarily nondormant Prunus avium (wild cherry) embryonic axes. The cDNA, designated Pa-RRM-GRP1 (Prunus avium RNA recognition motif glycine-rich protein 1), contains a single N-terminal RNA recognition motif (RRM) and single C-terminal glycine-rich domain. The glycine-rich domain is unusually long at 91 amino acids, 58 of which are glycines. The 534-base pair (bp) open reading frame (ORF) of this clone encodes a 178-amino-acid polypeptide with a predicted molecular weight of 17.33 kDa and pI of 7.84. Comparative sequence alignment of Pa-RRM-GRP1 reveals extensive homology to known and presumed glycine-rich RNA binding proteins from angiosperms and gymnosperms. Genomic Southern blot analysis suggests that this gene exists as a single copy in P. avium. Expression of this gene in P. avium embryonic axes during low-temperature dormancy-breaking treatments was studied and found to be induced by cold (3 degrees C) using real-time PCR of total cDNA supported by Northern blot analysis of total RNA. Expression dropped during prolonged storage at 3 degrees C and was reduced to control levels by interruption of cold treatment by warming to 20 degrees C.

Chemical analysis of volatiles emitted by Pinus svlvestris after induction by insect oviposition

Gas chromatography-mass spectrometry analyses of the headspace volatiles of Scots pine (Pinus sylvestris) induced by egg deposition of the sawfly Diprion pini were conducted. The odor blend of systemically oviposition-induced pine twigs. attractive for the eulophid egg parasitoid Chrysonotomyia ruforum, was compared to volatiles released by damaged pine twigs (control) that are not attractive for the parasitoid. The mechanical damage inflicted to the control twigs mimicked the damage by a sawfly female prior to egg deposition. The odor blend released by oviposition-induced pine twigs consisted of numerous mono- and sesquiterpenes, which all were also present in the headspace of the artificially damaged control twigs. A quantitative comparison of the volatiles from oviposition-induced twigs and controls revealed that only the amounts of (E)-beta-farnesene were significantly higher in the volatile blend of the oviposition-induced twigs. Volatiles from pine twigs treated with jasmonic acid (JA) also attract the egg parasitoid. No qualitative differences were detected when comparing the composition of the headspace of JA-treated pine twigs with the volatile blend of untreated control twigs. JA-treated pine twigs released significantly higher amounts of (E )-beta-farnesene. However, the JA treatment induced a significant increase of the amount of further terpenoid components. The release of terpenoids by pine after wounding, egg deposition, and JA treatment is discussed with special respect to (E)-beta-farnesene.

Salinity- and ABA-induced up-regulation and light-mediated modulation of mRNA encoding glycine-rich RNA-binding protein from Sorghum bicolor

Glycine-rich RNA-binding proteins play an important role in post-transcriptional regulation of gene expression, including RNA processing, and are known to be up-regulated in response to a number of external stimuli. However, their regulation in response to salinity stress has not been reported. We have isolated a light- and salt-regulated, full-length cDNA clone encoding a putative glycine-rich protein containing conserved ribonucleoprotein motif from Sorghum bicolor designated as sbGR-RNP. Sequence analysis of the 701bp insert revealed that the open reading frame of 513bp encodes a 170 amino acid protein, with an apparent molecular mass of 16.68kDa and calculated pI of 6.59. The deduced amino acid sequence also revealed that protein is hydrophilic in nature and contains 38% glycine residues. Northern blot analysis revealed a transcript size of 630 nucleotides, which shows regulation by blue and red light. The transcript is initially up- and down-regulated rapidly within 5min of irradiation with blue and red light, respectively. This kind of rapid and opposite regulation by different light wavelengths could be a novel behavior of this photo-regulated gene. Furthermore, NaCl (500mM) and abscisic acid (10 microM) also stimulated the transcript levels of sbGR-RNP to fourfold and sevenfold, respectively. These novel regulations of sbGR-RNP in response to light and salinity are important phenomena, which will be helpful in understanding the molecular mechanisms of cross-talk between abiotic stress and light signaling in plants.

Induction of chalcone synthase expression in white spruce by wounding and jasmonate

The phenylpropanoid pathway has important functions in angiospermous plants following exposure to environmental stresses, such as wounding and pathogen attack, that lead to production of compounds including lignin, flavonoids and phytoalexins. Chalcone synthase (CHS) is a key enzyme in this pathway, catalyzing the first step in flavonoid biosynthesis, whose expression can be induced in response to environmental stress. To explore the response of conifers to environmental stress, expression of spruce CHS and its inducibility were investigated. A partial spruce CHS cDNA clone was isolated using PCR. Examination of the expression patterns of the CHS gene family in white spruce revealed accumulation of CHS mRNA in needle tissue following mechanical wounding, or application of signal molecules like jasmonic acid or methyl jasmonate. Repeated mechanical wounding or jasmonate applications had an enhancing effect on transcript accumulation in needles. A systemic accumulation of CHS mRNAs following wounding was also observed. Conifers thus appear to possess a general wound response similar to that found for angiosperms, which includes CHS induction as well as its inducibility by jasmonic acid and airborne methyl jasmonate.