Abstract
The expression of hundreds of genes is induced by low temperatures via a cold signaling pathway. ICE1, a MYC-type transcription factor, plays an important role in the induction of CBF3/DREB1A to control cold-responsive genes and cold tolerance. To elucidate other molecular factors, a yeast 2-hybrid screening was performed. Two MYC-type transcription factors, MYC67 and MYC70, were identified as ICE1-interacting proteins. The myc mutants were more tolerant to freezing temperatures than wild type. CBF3/DREB1A and other cold-responsive genes were up-regulated in the myc mutants. Overexpression of the MYC genes increased the cold sensitivity and down-regulated the expression of cold-responsive genes. The MYC proteins interacted with the cis-elements in the CBF3/DREB1A promoter, probably to interfere interaction between ICE1 and the cis-elements. Taken together, these results demonstrate that MYC67 and MYC70, ICE1 interactors, negatively regulate cold-responsive genes and cold tolerance.
Highlights
Plant growth and development are highly affected by these environmental stresses, such as cold, drought, and salt stresses
Increased binding activity of ICE1 may enhance cold responsive gene transcription and tolerance. These results suggest that MYC67 or MYC70 inhibits interaction between ICE1 and MYC cis-elements, leading to negative regulation of cold tolerance
MYC-overexpression transgenic plants that were subjected to −6 °C for 4 hr after cold acclimation were more sensitive to freezing temperature than wild-type plants (Fig. 3C,D). These results indicate that MYC67 and MYC70 negatively regulate cold tolerance
Summary
Plant growth and development are highly affected by these environmental stresses, such as cold, drought, and salt stresses. Many tropical plants are cold-sensitive and significant losses of yield are observed under freezing temperatures, most temperate plants have ability to tolerate to freezing temperatures following a period of exposure to non-freezing temperatures This process is known as cold acclimation. The CBF (CRT-binding factor)/DREB1 (DRE-binding protein) proteins are a family of AP2-type transcription factors, which binds to the core sequence CCGAC of CRT/DRE cis-elements to induce expression of cold- and dehydration-responsive genes[4,5]. Increased binding activity of ICE1 may enhance cold responsive gene transcription and tolerance. These results suggest that MYC67 or MYC70 inhibits interaction between ICE1 and MYC cis-elements, leading to negative regulation of cold tolerance
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