The CONSTANS-like 4 transcription factor, AtCOL4, positively regulates abiotic stress tolerance through an abscisic acid-dependent manner in Arabidopsis

The precise roles of the B-box zinc finger family of transcription factors in plant stress are poorly understood. Functional analysis was performed on AtCOL4, an Arabidopsis thaliana L. CONSTANS-like 4 protein that is a putative novel transcription factor, and which contains a predicted transcriptional activation domain. Analyses of an AtCOL4 promoter--glucuronidase (GUS) construct revealed substantial GUS activity in whole seedlings. The expression of AtCOL4 was strongly induced by abscisic acid (ABA), salt, and osmotic stress. Mutation in atcol4 resulted in increased sensitivity to ABA and salt stress during seed germination and the cotyledon greening process. In contrast, AtCOL4-overexpressing plants were less sensitive to ABA and salt stress compared to the wild type. Interestingly, in the presence of ABA or salt stress, the transcript levels of other ABA biosynthesis and stress-related genes were enhanced induction in AtCOL4-overexpressing and WT plants, rather than in the atcol4 mutant. Thus, AtCOL4 is involved in ABA and salt stress response through the ABA-dependent signaling pathway. Taken together, these findings provide compelling evidence that AtCOL4 is an important regulator for plant tolerance to abiotic stress.