| Summary: | <p>Abstract</p> <p>Background</p> <p>Plants respond to low temperature through an intricately coordinated transcriptional network. The <it>CBF/DREB</it>-regulated network of genes has been shown to play a prominent role in freeze-tolerance of <it>Arabidopsis </it>through the process of cold acclimation (CA). Recent evidence also showed that the <it>CBF/DREB </it>regulon is not unique to CA but evolutionarily conserved between chilling-insensitive (temperate) and chilling-sensitive (warm-season) plants. In this study, the wide contrast in chilling sensitivity between indica and japonica rice was used as model to identify other regulatory clusters by integrative analysis of promoter architecture (<it>ab initio</it>) and gene expression profiles.</p> <p>Results</p> <p>Transcriptome analysis in chilling tolerant japonica rice identified a subset of 121 '<it>early response</it>' genes that were upregulated during the initial 24 hours at 10°C. Among this group were four transcription factors including <it>ROS-bZIP1 </it>and another larger sub-group with a common feature of having as1/ocs-like elements in their promoters. Cold-induction of <it>ROS-bZIP1 </it>preceded the induction of as1/ocs-like element-containing genes and they were also induced by exogenous H<sub>2</sub>O<sub>2 </sub>at ambient temperature. Coordinated expression patterns and similar promoter architectures among the '<it>early response</it>' genes suggest that they belong to a potential regulon (<it>ROS-bZIP – as1/ocs </it>regulatory module) that responds to elevated levels of ROS during chilling stress. Cultivar-specific expression signatures of the candidate genes indicate a positive correlation between the activity of the putative regulon and genotypic variation in chilling tolerance.</p> <p>Conclusion</p> <p>A hypothetical model of an ROS-mediated regulon (<it>ROS-bZIP – as1/ocs</it>) triggered by chilling stress was assembled in rice. Based on the current results, it appears that this regulon is independent of ABA and <it>CBF/DREB</it>, and that its activation has an important contribution in configuring the rapid responses of rice seedlings to chilling stress.</p>
|
|---|