Abstract
Plants adapt to adverse environmental conditions through physiological responses, such as induction of the abscisic acid signaling pathway, stomatal regulation, and root elongation. Altered gene expression is a major molecular response to adverse environmental conditions in plants. Several transcription factors function as master switches to induce the expression of stress-tolerance genes. To find out a master regulator for the cold stress tolerance in rice, we focused on functionally identifying DREB subfamily which plays important roles in cold stress tolerance of plants. Here, we characterized OsDREB1G (LOC_Os02g45450), a functionally unidentified member of the DREB1 subgroup. OsDREB1G is specifically induced under cold stress conditions among several abiotic stresses examined. This gene is dominantly expressed in leaf sheath, blade, node, and root. Transgenic rice overexpressing this gene exhibited strong cold tolerance and growth retardation, like transgenic rice overexpressing other OsDREB1 genes. However, unlike these rice lines, transgenic rice overexpressing OsDREB1G did not exhibit significant increases in drought or salt tolerance. Cold-responsive genes were highly induced in transgenic rice overexpressing DREB1G compared to wild type. In addition, OsDREB1G overexpression directly induced the expression of a reporter gene fused to the promoters of cold-induced genes in rice protoplasts. Therefore, OsDREB1G is a typical CBF/DREB1 transcription factor that specifically functions in the cold stress response. Therefore, OsDREB1G could be useful for developing transgenic rice with enhanced cold-stress tolerance.
Highlights
Plant growth and crop productivity are strongly affected by environmental stresses such as drought, salt, and low temperature
We found that Os02g45450 was expressed in response to cold stress, with an expression profile similar to those of OsDREB1A and OsDREB1B (Figure 1B)
Os02g45450 was closest to OsDREB1E and OsDREB1F in a phylogenic tree constructed based on amino acid sequences (Figure 1A)
Summary
Plant growth and crop productivity are strongly affected by environmental stresses such as drought, salt, and low temperature. OsDREB1G Functions in Cold Stress is regulated by numerous transcription factors (TF), such as MYB, bZIP, WRKY, AP2/ERF, and bHLH TFs (Shinozaki and Yamaguchi-Shinozaki, 2007; Golldack et al, 2011; Moon et al, 2015). Most stress-related TFs bind to specific cis-elements in the promoter regions of numerous stress-inducible downstream genes to activate their transcription, thereby functioning as key regulators of abiotic stress tolerance (Agarwal et al, 2006; Hussain et al, 2011). One group of transcription factors involved in abiotic stress tolerance is the dehydration responsive element binding (DREB) transcription factor subfamily. DREB transcription factors bind to the DNA sequence motif G/ACCGAC (known as the dehydration responsive element (DRE)/C-repeat; DRE/CRT) found in various cold- and drought-responsive genes (Stockinger et al, 1997; Shinwari et al, 1998). DREB1/CBF TFs primarily function in cold stress, while DREB2 TFs function in drought and salt stress (Liu et al, 1998)
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