Gene expression under cold stress in Arabidopsis

Abstract

Microarray analysis and mutational approaches were used to investigate regulation of freezing tolerance in plants. Using Arabidopsis, cold-responsive gene expression profiling was performed with Affymetrix GeneChip. Arabidopsis seedlings were cold-treated at 0°C for 0, 3, 6, and 24 hrs. A total of 681 cold-responsive genes were identified. Comparison of the expression profile of cold-responsive genes in the wild type to that of ice1, a mutant defective in cold stress signaling, showed altered transcript levels for many cold-responsive genes in the ice1 mutant even under non-stress conditions, which may explain its altered sensitivity to cold stress. To dissect the regulatory mechanism of cold-responsive gene expression, Arabidopsis plants expressing the luciferase gene driven by stress-responsive promoters were mutated and screened for altered luminescence. fro1 (frostbite 1),fro2 (frostbite 2), and stab1 (stabilized 1) were characterized and the genes responsible for the mutant phenotypes were identified. fro1 showed a lower expression of the stress-responsive RD29A promoter-driven luciferase transgene and endogenous RD29A gene under cold than the wild type. FRO1 encodes a component of complex I in the mitochondrial electron transport chain. These results suggested that cold-inducible gene expression is modulated by the functional status of mitochondria. fro2 was identified from Arabidopsis expressing the CBF3 promoter driven-luciferase transgene, because of its lower luminescence induction under cold. fro2 also showed lower expression of endogenous CBF genes under cold. FRO2 encodes a serine decarboxylase that converts serine to ethanolamine. This result indicated the importance of serine metabolism in CBF gene regulation. stab1 showed higher expression of RD29A promoter-controlled luciferase after stress, but the level of endogenous RD29A transcript was not different from that of the wild type after stress. Nuclear run-on assays suggested that this discrepancy was due to the enhanced stability of the luciferase mRNA. STAB1 encodes a splicing factor similar to the human U5 snRNP-associated 102-kDa protein. stab1 displayed hypersensitivity to cold and altered sensitivity to various stress. These results suggested that STAB1 is required for not only splicing but also the turnover of unstable transcripts and that it has an important role in plant tolerance to abiotic stresses, particularly cold.