Functional Analysis Of Rice AP2/EREBP Transcription Factor Gene OsASIE1

Abiotic stresses are major constraint of crop productivity. Identifying genes related to plant stresstolerance will provide genetic resource for breeding stress tolerance crop varieties by geneticengineering. In the evolution, plants have developed diverse mechanisms to adapt environmentalstresses at the molecular, cellular, physiological and biochemical level. Transcription factors are masterregulators that control gene clusters and play an important role in plant stress response. As one of themost important transcription factor families in plant, AP2/EREBP transcription factors play animportant role in plant development, hormone response, biotic and abiotic stress response.Ubiquitination involved in a variety of biological processes, recent studies indicate that it plays a role inabiotic stress. In order to discover AP2/EREBP transcription factor genes and E3 ligase genes involvedin stress response of rice, several drought stress-induced AP2/EREBP transcription factor genes and E3ligase genes identified by microarray were selected for the functional identification of stress tolerance inrice in this study. The main results are as follows:1. Expression profiles of eight drought stress-induced AP2/EREBP transcription factor genesidentified by microarray analysis were performed by using quantitative Real-time PCR. The resultshows that most of genes have the similar expression pattern in Nippobare (sensitive to drought and salt)IRAT109 (tolerant to drought), LTH (tolerant to cold stress) and FL478 (salt tolerant). But the genes ofOs03g08470 and Os07g42510 were shown down-regulated in Nippobare, but up-regulated in IRAT109under drought stress, indicating that they might be involved in specific stress response pathway inIRAT109. The expression of OsASIE1 was induced by drought, salt, cold stresses in both leaves androots. Further analysis indicated that OsASIE1 was immediately induced under drought and salt stress,implying that OsASIE1 was involved in early stress response of rice plant.2. Electrophoresis mobility shift assay (EMSA) was applied to identify if AP2 domain of threeAP2/EREBP transcription factor (Os03g08460, Os03g08470, OsASIE1) could bind DRE (dehydrationresponsiveelement) and GCC box (ethylene response element, ERE) in vitro. Results showed that theAP2 domain of OsASIE1 could bind both DRE and GCC box.3. Over-expression vectors of three AP2/EREBP genes (Os03g08460, Os03g08470, OsASIE1) andfour putative E3 ligase gene (Os07g47590, Os04g44820, Os04g01490, Os10g40490), and RNAisuppression vectors of two AP2/EREBP genes (Os03g08460, Os03g08470) and two putative E3 ligasegenes (Os04g44820,Os10g40490) were constructed. All vectors were transformed into Nippobare.Phenotypes analysis showed that these over-expression transgenic rice plants were shown improved salttolerance.In conclusion, our results indicated that the gene OsASIE1 was related to rice salt stress response. Theexpression of OsASIE1 was induced rapidly under salt stress, and then downstream genes involved inrice stress response were activated. However, the molecular mechanism of OsASIE1 involved in stressresponse need to be further elucidated.