水稻bZIP转录因子OsbZIPX1在耐旱胁迫应答中的分子机理

bZIP transcription factor family plays an important role in the abiotic stress signaling pathway in plants, but its regulatory mechanism is poorly understood. Using large-scale gene expression and transgenic plant analyses, we obtained a member of bZIP transcription factor family, OsbZIPX1, which is specifically induced by mannitol and suggests it might act as a positive regulator in drought stress response of rice. Function analysis showed that OsbZIPX1 is a nuclear localized protein specifically binds to the G-box motif, but without transcriptional activity. In yeast two-hybrid experiment, OsbZIPX1 can form both homodimer or heterodimer with Group C of bZIP family members. Transgenic plant analysis showed that OsbZIPX1 over-expressing plants had dramatically improved drought tolerance and OsbZIPX1 RNAi lines showed sensitivity to drought. However, no significant difference in other agronomic traits between transgenic rice lines and wild-type was found. In this proposed study, we would like to investigate the mechanism of OsbZIPX1 involved in drought stress response by using genetics, molecular biology, and biochemistry means, and also explore its possible application in rice drought tolerance improvement.

干旱严重影响我国农业生产，克隆有重要应用价值的耐旱基因并培育耐旱作物新品种具有重要意义。bZIP转录因子家族在植物耐逆信号途径中起重要作用，但其调控机制知之甚少。通过大规模表达分析和高通量转基因水稻筛选，我们获得一特异性受甘露醇特异诱导的bZIP转录因子成员OsbZIPX1。研究表明，OsbZIPX1定位于细胞核，但自身并没转录激活活性。酵母实验表明，OsbZIPX1能结合G-Box，且既能形成同源二聚体，也可与bZIP家族其它成员形成异源二聚体。在正常条件下，过量表达OsbZIPX1转基因水稻显著提高了水稻耐受干旱胁迫能力，而RNAi水稻则表现出对干旱的敏感性。生物信息学预测及酵母双杂试验表明，OsbZIPX1可能受OsSnRK激酶调节。本申请拟进一步利用遗传学、分子生物学和生化等技术深入研究OsbZIPX1在响应干旱逆境胁迫中的分子机理，探索OsbZIPX1在水稻抗旱改良上的应用潜力。

干旱严重影响我国农业生产，因此，克隆具有重要应用价值的耐旱基因并培育耐逆作物新品种具有重要意义。bZIP转录因子家族在植物耐逆信号途径中起重要作用，但其调控机制仍知之甚少。通过大规模表达分析和高通量转基因水稻筛选，我们获得一特异性受干旱、PEG和ABA诱导的bZIP转录因子成员OsbZIP71。研究结果表明OsbZIP71定位于细胞核，但自身并没有转录激活活性。酵母实验表明，OsbZIP71既能形成同源二聚体，也能与bZIP家族的Group C亚家族成员以及OsMyb4形成异源二聚体结合G-Box。转基因实验表明，组成型过表达OsbZIP71 (p35S::OsbZIP71)及干旱诱导表达OsbZIP71 (RD29A::OsbZIP71)水稻株系极显著性地提高了水稻耐受干旱胁迫能力，而OsbZIP71 RNAi株系对干旱敏感，同时也对ABA超敏感。这些结果表明，OsbZIP71是一个参与ABA依赖途径的耐旱正调控因子。利用基因芯片技术获得了大量OsbZIP71下游调控基因，进一步利用Realtime技术验证了OsbZIP71逆境调控基因。ChIP-qPCR验证OsbZIP71直接结合OsNHX1 和COR413-TM1的含G-box的片段启动子区。总之，水稻遇到干旱时，OsbZIP71通过ABA依赖途径，与OsMyb4形成复合体，结合OsNHX1 和COR413-TM1的含G-box的片段启动子区，进而提高水稻对干旱的耐受能力。在应用方面，利用干旱诱导型启动子RD29A调控OsbZIP71，极显著地提高了水稻对干旱的耐受性，但对其它农业性状不受影响。这表明OsbZIP71对水稻耐旱的分子设计改良具有巨大的应用价值和潜力。