STRESS RESPONSE SUPPRESSOR1 and STRESS RESPONSE SUPPRESSOR2, Two DEAD-Box RNA Helicases That Attenuate Arabidopsis Responses to Multiple Abiotic Stresses

摘要

Two genes encoding Arabidopsis (Arabidopsis thaliana) DEAD-box RNA helicases were identified in a functional genomics screennas being down-regulated bymultiple abiotic stresses.Mutations in either gene caused increased tolerance to salt, osmotic, andnheat stresses, suggesting that the helicases suppress responses to abiotic stress. The genes were therefore designated STRESSnRESPONSE SUPPRESSOR1 (STRS1;At1g31970) and STRS2 (At5g08620). In the strsmutants, salt, osmotic, and cold stresses inducednenhanced expression of genes encoding the transcriptional activators DREB1A/CBF3 and DREB2A and a downstreamnDREB target gene, RD29A. Under heat stress, the strs mutants exhibited enhanced expression of the heat shock transcriptionnfactor genes, HSF4 and HSF7, and the downstream gene HEAT SHOCK PROTEIN101. Germination of mutant seed wasnhyposensitive to the phytohormone abscisic acid (ABA), butmutants showed up-regulated expression of genes encodingABAdependentnstress-responsive transcriptional activators and their downstream targets. In wild-type plants, STRS1 and STRS2nexpression was rapidly down-regulated by salt, osmotic, and heat stress, but not cold stress. STRS expression was also reducednbyABA, but salt stress led to reduced STRS expression in bothwild-type andABA-deficient mutant plants. Taken together, ournresults suggest that STRS1 and STRS2 attenuate the expression of stress-responsive transcriptional activators and function innABA-dependent and ABA-independent abiotic stress signaling networks.