Functional Analysis Of OsAREB1, A BZIP Transcription Factor In Rice (Oryza Sativa L.)

Drought, high salinity and extremely temperature are the most severe disasters of abiotic stresses harm to crops, and researchers have paid attention to the studies on these abiotic stresses for a long time. Plants sense the stresses and active corresponding signal transduction pathway to induce the expression of stress-responded genes, during these responding processes, transcription factors (TFs) plays a key role. Based on the structure character and DNA-binding specificity, TFs can be divided into several families, such as bZIP, AP2/EREBP, MYB,WRKY and so on in plants, all of these TFs functioned in stress responding processes. In this study, in order to study the relationship of transcription factors with anti-abiotic stresses in plants, a bZIP transcription factor gene OsAREB1 was cloned from rice, which encoded a protein with a whole open reading frame (ORF).The expression patterns of OsAREB1 were detected in diverse tissues of rice and with different treatments by RT-PCR. The results indicated that OsAREB1 was mainly expressed in root of rice, and can be induced by ABA, PEG, NaCl and heat, but not by cold.TFs can regulate the gene expression by combining to the cis-element in the promoter region of target functional genes. Yeast one- hybrid essay was used to test the binding ability between OsAREB1 and ABRE cis-element, and the results shown they could combine to each other normally.Analysis of over expressing OsAREB1 in transgenic plant suggested that over-expression of OsAREB1 in transgenic Arabidopsis made the cotyledon insensitive to ABA and root hypersensitive to ABA. With high water content and low water lose rate, transgenic plants display drought resistance. Additionally, transgenic plants also exhibit heat stress tolerance. The results of RT-PCR for RD29A, RD29B and AtNCED3 genes implied that OsAREB1 over-expressed plants had a high expression level of these genes compared to the WT plants, and drought and heat treatments could enlarge these differences. Surprisingly, the expression of heat shock proteins (HsfA2,HSP70 and HSP80) which play important roles in heat stress had higher expression levels of these HSPs in transgenic plants than that of WT before heat treatment. But there're no differences between WT and transgenic plants in HSPs expression level after heat treatment.It is reasonable to presume that OsAREB1 participates in ABA-dependent signaling transducation pathway and can enhance drought and heat tolerances for transgenic Arabidopsis based on research results. But more work need to do to elucidate the mechanism of OsAREB1 in drought and heat tolerances in plant.