Abstract
The clustered genes C-repeat (CRT) binding factor (CBF)1/ dehydration-responsive element binding protein (DREB)1B, CBF2/DREB1C, and CBF3/DREB1A play a central role in cold acclimation and facilitate plant resistance to freezing in Arabidopsis thaliana. Rice (Oryza sativa L.) is very sensitive to low temperatures; enhancing the cold stress tolerance of rice is a key challenge to increasing its yield. In this study, we demonstrate chilling acclimation, a phenomenon similar to Arabidopsis cold acclimation, in rice. To determine whether rice CBF/DREB1 genes participate in this cold-responsive pathway, all putative homologs of Arabidopsis DREB1 genes were filtered from the complete rice genome through a BLASTP search, followed by phylogenetic, colinearity and expression analysis. We thereby identified 10 rice genes as putative DREB1 homologs: nine of these were located in rice genomic regions with some colinearity to the Arabidopsis CBF1–CBF4 region. Expression profiling revealed that six of these genes (Os01g73770, Os02g45450, Os04g48350, Os06g03670, Os09g35010, and Os09g35030) were similarly expressed in response to chilling acclimation and cold stress and were co-expressed with genes involved in cold signalling, suggesting that these DREB1 homologs may be involved in the cold response in rice. The results presented here serve as a prelude towards understanding the function of rice homologs of DREB1 genes in cold-sensitive crops.
Highlights
Low temperature is one of the adverse environmental factors that can limit crop distribution and productivity
DDF2, had three pairs of paralogs (AT1G12560/AT1G62980, DDF1/DDF2, or AT1G12640/AT1G63050). All these results indicated that the clustered genes (CBF1–CBF3) and CBF4, equivalent to DDF1 and DDF2, were paralogous to each other, and were likely derived from two rounds of segmental duplication
We have ascertained that rice possesses 10 homologs of Arabidopsis DREB1 genes, which is consistent with previous reports that up to 10 DREB1-like genes exist in the rice genome [12, 13, and 14]
Summary
Low temperature is one of the adverse environmental factors that can limit crop distribution and productivity. The molecular mechanism of the C-repeat (CRT) binding factor/dehydration-responsive element binding protein 1 (CBF/DREB1)-dependent cold-responsive signal pathway has been studied in depth in the freezing-tolerant plant Arabidopsis thaliana [3]. Three CBF genes, CBF1/DREB1B, CBF2/DREB1C, and CBF3/DREB1A, play a central role in this pathway These genes belong to a small subfamily of the ethylene response factor/ Apetala (ERF/AP2) family, named the DREB1 family that contains six members (i.e. CBF1–CBF4, DDF1, and DDF2). Besides the ERF/AP2 domain, the six genes have special conserved domains or motifs (the nuclear localization signal [NLS], DSAWR, and LWSY motifs) [4] These genes encode DREB1 proteins - transcription factors that recognise the C-repeat elements of cold-responsive genes (CORs) and activate their expression. Arabidopsis CBF1–CBF3 play central roles in the cold responsive pathway
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