Abstract
BackgroundPathogenesis-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 ABR17 cDNA in Arabidopsis thaliana and Brassica napus 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 ABR17 transgenic A. thaliana may shed light on this process.ResultsThe molecular changes brought about by the expression of pea ABR17 cDNA in A. thaliana in the presence or absence of salt stress were investigated using microarrays consisting of 70-mer oligonucleotide probes representing 23,686 Arabidopsis 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 ABR17 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.ConclusionTranscriptional analysis in ABR17 transgenic Arabidopsis 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 ABR17 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.
Highlights
Pathogenesis-related proteins belonging to group 10 (PR10) are elevated in response to biotic and abiotic stresses in plants
RNase activities have been detected for many PR10 proteins, they have been shown to interact with molecules such as cytokinins (CKs), brassinosteroids, fatty acids, and flavonoids [9,10,11]
We have demonstrated that the constitutive expression of pea PR10.1 and ABR17 cDNAs enhance germination and early seedling growth under abiotic stress conditions in B. napus and A. thaliana, respectively [18,19]
Summary
Pathogenesis-related proteins belonging to group 10 (PR10) are elevated in response to biotic and abiotic stresses in plants. PR10 genes were first described in Pisum sativum inoculated with Fusarium solani [4] but have been subsequently described in many species [reviewed in [3]] In addition to their inducible expression in response to stresses, PR10 genes exhibit constitutive high expressed levels in roots, flowers and pollen during normal growth and development, suggesting additional roles beyond pathogenesis responses [5]. RNase activities have been detected for many PR10 proteins, they have been shown to interact with molecules such as cytokinins (CKs), brassinosteroids, fatty acids, and flavonoids [9,10,11] These observations have led to the suggestion that all PR10 proteins may not be RNases and may be involved during normal plant growth and development as hormone/ligand carriers [10,11,12]. This suggestion is further supported by the fact that CK-specific binding proteins (CSBPs) exhibit amino acid sequence and predicted secondary-structure similarities with PR10 proteins and, for this reason, have been included in the PR10 family [9]
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