Transcriptional profiling of pea ABR17 mediated changes in gene expression in Arabidopsis thaliana

<p>Abstract</p> <p>Background</p> <p>Pathogenesis-related proteins belonging to group 10 (PR10) are elevated in response to biotic and abiotic stresses in plants. Previously, we have shown a drastic salinity-induced increase in the levels of ABR17, a member of the PR10 family, in pea. Furthermore, we have also demonstrated that the constitutive expression of pea <it>ABR17 </it>cDNA in <it>Arabidopsis thaliana </it>and <it>Brassica napus </it>enhances their germination and early seedling growth under stress. Although it has been reported that several members of the PR10 family including ABR17 possess RNase activity, the exact mechanism by which the aforementioned characteristics are conferred by ABR17 is unknown at this time. We hypothesized that a study of differences in transcriptome between wild type (WT) and <it>ABR17 </it>transgenic <it>A. thaliana </it>may shed light on this process.</p> <p>Results</p> <p>The molecular changes brought about by the expression of pea <it>ABR17 </it>cDNA in <it>A. thaliana </it>in the presence or absence of salt stress were investigated using microarrays consisting of 70-mer oligonucleotide probes representing 23,686 <it>Arabidopsis </it>genes. Statistical analysis identified number of genes which were over represented among up- or down-regulated transcripts in the transgenic line. Our results highlight the important roles of many abscisic acid (ABA) and cytokinin (CK) responsive genes in <it>ABR17 </it>transgenic lines. Although the transcriptional changes followed a general salt response theme in both WT and transgenic seedlings under salt stress, many genes exhibited differential expression patterns when the transgenic and WT lines were compared. These genes include plant defensins, heat shock proteins, other defense related genes, and several transcriptional factors. Our microarray results for selected genes were validated using quantitative real-time PCR.</p> <p>Conclusion</p> <p>Transcriptional analysis in <it>ABR17 </it>transgenic <it>Arabidopsis </it>plants, both under normal and saline conditions, revealed significant changes in abundance of transcripts for many stress responsive genes, as well as those related to plant growth and development. Our results also suggest that <it>ABR17 </it>may mediate stress tolerance through the modulation of many ABA- and CK-responsive genes and may further our understanding of the role of ABR17 in mediating plant stress responses.</p

Identification and expression analysis of <it>WRKY </it>transcription factor genes in canola <it>(Brassica napus </it>L.) in response to fungal pathogens and hormone treatments

<p>Abstract</p> <p>Background</p> <p>Members of plant WRKY transcription factor families are widely implicated in defense responses and various other physiological processes. For canola (<it>Brassica napus </it>L.), no WRKY genes have been described in detail. Because of the economic importance of this crop, and its evolutionary relationship to <it>Arabidopsis thaliana</it>, we sought to characterize a subset of canola <it>WRKY </it>genes in the context of pathogen and hormone responses.</p> <p>Results</p> <p>In this study, we identified 46 <it>WRKY </it>genes from canola by mining the expressed sequence tag (EST) database and cloned cDNA sequences of 38 <it>BnWRKY</it>s. A phylogenetic tree was constructed using the conserved WRKY domain amino acid sequences, which demonstrated that BnWRKYs can be divided into three major groups. We further compared <it>BnWRKYs </it>to the 72 <it>WRKY </it>genes from <it>Arabidopsis </it>and 91 <it>WRKY </it>from rice, and we identified 46 presumptive orthologs of <it>AtWRKY </it>genes. We examined the subcellular localization of four BnWRKY proteins using green fluorescent protein (GFP) and we observed the fluorescent green signals in the nucleus only.</p> <p>The responses of 16 selected <it>BnWRKY </it>genes to two fungal pathogens, <it>Sclerotinia sclerotiorum </it>and <it>Alternaria brassicae</it>, were analyzed by quantitative real time-PCR (qRT-PCR). Transcript abundance of 13 <it>BnWRKY </it>genes changed significantly following pathogen challenge: transcripts of 10 <it>WRKY</it>s increased in abundance, two <it>WRKY </it>transcripts decreased after infection, and one decreased at 12 h post-infection but increased later on (72 h). We also observed that transcript abundance of 13/16 <it>BnWRKY </it>genes was responsive to one or more hormones, including abscisic acid (ABA), and cytokinin (6-benzylaminopurine, BAP) and the defense signaling molecules jasmonic acid (JA), salicylic acid (SA), and ethylene (ET). We compared these transcript expression patterns to those previously described for presumptive orthologs of these genes in <it>Arabidopsis </it>and rice, and observed both similarities and differences in expression patterns.</p> <p>Conclusion</p> <p>We identified a set of 13 <it>BnWRKY </it>genes from among 16 <it>BnWRKY </it>genes assayed, that are responsive to both fungal pathogens and hormone treatments, suggesting shared signaling mechanisms for these responses. This study suggests that a large number of BnWRKY proteins are involved in the transcriptional regulation of defense-related genes in response to fungal pathogens and hormone stimuli.</p