The Arabidopsis thaliana CBF cold response pathway plays a central role in cold acclimation. It is characterized by rapid cold induction of genes encoding the CBF1-3 transcription factors, followed by expression of the CBF gene regulon, which imparts freezing tolerance. Our goal was to further the understanding of the cis-acting elements and trans-acting factors involved in expression of CBF2. We identified seven conserved DNA motifs (CM), CM1 to 7, that are present in the promoters of CBF2 and another rapidly cold-induced gene encoding a transcription factor, ZAT12. The results presented indicate that in the CBF2 promoter, CM4 and CM6 have negative regulatory activity and that CM2 has both negative and positive activity. A Myc binding site in the CBF2 promoter was also found to have positive regulatory effects. Moreover, our results indicate that members of the calmodulin binding transcription activator (CAMTA) family of transcription factors bind to the CM2 motif, that CAMTA3 is a positive regulator of CBF2 expression, and that double camta1 camta3 mutant plants are impaired in freezing tolerance. These results establish a role for CAMTA proteins in cold acclimation and provide a possible point of integrating low-temperature calcium and calmodulin signaling with cold-regulated gene expression.
Significant differences in seedling vigor exist among sugar beet (Beta vulgaris) hybrids; however, traditional approaches to breeding enhanced vigor have not proven effective. Seedling vigor is a complex character, but presumably includes efficient mobilization of seed storage reserves during germination and efficient seedling growth in diverse environments. The involvement of lipid metabolism during germination of sugar beet under stress conditions was suggested by the isolation at high frequency of Expressed Sequence Tags (ESTs) with similarity to isocitrate lyase (EC 4.1.3.1). High-level expression of this glyoxylate cycle enzyme during germination and seedling emergence was also suggested by nucleotide sequencing of cDNA libraries obtained from a well emerging sugar beet hybrid during germination under stress. Genes involved in carbohydrate and lipid catabolism were differentially expressed in a strongly emerging hybrid, relative to a weakly emerging hybrid, during stress germination. Stress markedly reduced the levels of alpha-amylase transcripts in the weakly emerging hybrid. In contrast, the strongly emerging hybrid exhibited only a moderate reduction in alpha-amylase transcript levels under the same conditions, and showed large increases in the expression of genes involved in lipid metabolism, suggesting compensation by lipid for carbohydrate metabolism in the better emerging hybrid. Differential activity of the glyoxylate cycle thus appears to be a physiological marker that distinguishes between high- and low-vigor sugar beet cultivars. This finding suggests, for the first time, a biochemical target for selection for enhanced germination and improved emergence in sugar beet.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.