BrRH37, a Cabbage (Brassica rapa) DEAD-Box RNA Helicase, Confers Drought Tolerance and ABA Response in Transgenic Arabidopsis Plants

Abstract

RNA helicases (RHs) are cellular proteins that help in the regulation of post-transcriptional mRNA metabolism, which is vital for the response of crops to abiotic stresses. In this study, we determined the functional role of a cabbage (Brassica rapa) DEAD-box RH, BrRH37, in abiotic stress and abscisic acid (ABA) responses using transgenic Arabidopsis plants. Although BrRH37 contains a putative chloroplast transit peptide and a potential nuclear localization signal, confocal analysis of the expression of the BrRH37-GFP protein in tobacco leaves revealed that BrRH37 is localized in the nucleus. The transcript levels of BrRH37 in cabbage were increased upon drought, cold, or ABA application, whereas its level was decreased by heat or UV stress. The transgenic Arabidopsis plants that constitutively express BrRH37 showed enhanced seedling and root growth or survival rate under drought stress or upon ABA application, whereas their growth and survival were decreased under cold or UV stress. Notably, transcript levels of ABA biosynthesis-related genes, including ABA1 and ABA3, were significantly increased in the transgenic plants compared with that in the wild type. Importantly, BrRH37 was found to recover the growth of the RNA chaperone-deficient Escherichia coli mutant at low temperature and had the ability to break up base pairs in RNA, suggesting that BrRH37 possesses RNA chaperone activity. Altogether, our results indicate that BrRH37 plays diverse functions in plant response to abiotic stress and ABA possibly via its RNA chaperone activity.