Overexpression of an ERF transcription factor TSRF1 improves rice drought tolerance.

One of the major limitations in rice production is a shortage of water. Conventional breeding as well as emerging genetic engineering methods may be used to improve plant stress tolerance. Some transcription factors regulating stress responsive genes have become important target genes for improving plant drought tolerance. Previously, we have shown that a tomato ethylene response factor (ERF) protein TSRF1 that binds to GCC box in the promoters of pathogenesis-related genes positively regulates pathogen resistance in tomato and tobacco, but negatively regulates osmotic response in tobacco. Here, we further report the ability of TSRF1 to regulate osmotic and drought responses in monocot rice. TSRF1 improves the osmotic and drought tolerance of rice seedlings without growth retardation, as determined by physiological analyses of root and leaf growth, leaf water loss and survival rate under stress. In addition, the amounts of proline and soluble sugars in transgenic rice lines increase by 30%-60% compared to those in wild-type plants. Moreover, TSRF1 activates the expression of a putative rice abscisic acid (ABA) synthesis gene SDR, resulting in enhanced ABA sensitivity in transgenic rice. TSRF1 also increases the expression of MYB, MYC and proline synthesis and photosynthesis-related genes, probably by binding to dehydration responsive element and GCC boxes in promoters of the target genes. These results demonstrate that TSRF1 enhances the osmotic and drought tolerance of rice by modulating the increase in stress responsive gene expression.