Genome-wide analysis of WRKY gene family in Cucumis sativus

<p>Abstract</p> <p>Background</p> <p>WRKY proteins are a large family of transcriptional regulators in higher plant. They are involved in many biological processes, such as plant development, metabolism, and responses to biotic and abiotic stresses. Prior to the present study, only one full-length cucumber WRKY protein had been reported. The recent publication of the draft genome sequence of cucumber allowed us to conduct a genome-wide search for cucumber WRKY proteins, and to compare these positively identified proteins with their homologs in model plants, such as <it>Arabidopsis</it>.</p> <p>Results</p> <p>We identified a total of 55 WRKY genes in the cucumber genome. According to structural features of their encoded proteins, the cucumber WRKY (<it>CsWRKY</it>) genes were classified into three groups (group 1-3). Analysis of expression profiles of <it>CsWRKY </it>genes indicated that 48 WRKY genes display differential expression either in their transcript abundance or in their expression patterns under normal growth conditions, and 23 WRKY genes were differentially expressed in response to at least one abiotic stresses (cold, drought or salinity). The expression profile of stress-inducible <it>CsWRKY </it>genes were correlated with those of their putative <it>Arabidopsis WRKY (AtWRKY) </it>orthologs, except for the group 3 WRKY genes. Interestingly, duplicated group 3 <it>AtWRKY </it>genes appear to have been under positive selection pressure during evolution. In contrast, there was no evidence of recent gene duplication or positive selection pressure among <it>CsWRKY </it>group 3 genes, which may have led to the expressional divergence of group 3 orthologs.</p> <p>Conclusions</p> <p>Fifty-five WRKY genes were identified in cucumber and the structure of their encoded proteins, their expression, and their evolution were examined. Considering that there has been extensive expansion of group 3 WRKY genes in angiosperms, the occurrence of different evolutionary events could explain the functional divergence of these genes.</p

Characterization of wound responsive genes in Aquilaria malaccensis.

We report on the isolation and characterization of several genes responsive to wounding in the tropical endangered tree Aquilaria malaccensis. Wounding triggers the formation of a fragrant substance inside the tree stem. Deduced amino acid of the cloned sequences exhibited sequence similarities to their respective homologs: transcription factors of the WRKY gene family (AmWRKY) and β-1,3-glucanase (AmGLU). A homolog to phenylalanine ammonia-lyase (AmPAL) from previous work was also included. All cDNA sequences were of partial lengths. We studied their expression profiles in a wounding-stress experiment. Mechanical wounding induces AmWRKY in an early response to wounding (3 h), and elevates AmPAL and AmGLU expressions after 16 h. It is possible that AmWRKY mediates early wounding response while AmPAL mediates response to fungal infection by co-inducing AmGLU. Their homologs in other plants are known to inhibit fungal growth. Our data provide the first insight into the mechanisms of wounding responses in Aquilaria

Ion homeostasis in the Chloroplast

peer reviewedThe chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess, homeostasis mechanisms must be tightly regulated. Here, we describe the needs for nutrient ions in the chloroplast and briefly highlight their functions in the chloroplastidial metabolism. We further discuss the impact of nutrient deficiency on chloroplasts and the acclimation mechanisms that evolved to preserve the photosynthetic apparatus. We finally present what is known about import and export mechanisms for these ions. Whenever possible, a comparison between cyanobacteria, algae and plants is provided to add an evolutionary perspective to the description of ion homeostasis mechanisms in photosynthesis

Isolation and characterization of a Vitis vinifera transcription factor, VvWRKY1, and its effect on responses to fungal pathogens in transgenic tobacco plants

International audiencePathogen attack represents a major problem for viticulture and for agriculture in general. At present, the use of phytochemicals is more and more restrictive, and therefore it is becoming essential to control disease by having a thorough knowledge of resistance mechanisms. The present work focused on the trans-regulatory proteins potentially involved in the control of the plant defence response, the WRKY proteins. A full-length cDNA, designated VvWRKY1, was isolated from a grape berry library (Vitis vinifera L. cv. Cabernet Sauvignon). It encodes a polypeptide of 151 amino acids whose structure is characteristic of group IIc WRKY proteins. VvWRKY1 gene expression in grape is regulated in a developmental manner in berries and leaves and by various signal molecules involved in defence such as salicylic acid, ethylene, and hydrogen peroxide. Biochemical analysis indicates that VvWRKY1 specifically interacts with the W-box in various nucleotidic contexts. Functional analysis of VvWRKY1 was performed by overexpression in tobacco, and transgenic plants exhibited reduced susceptibility to various fungi but not to viruses. These results are consistent with a possible role for VvWRKY1 in grapevine defence against fungal pathogens