Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.
Mol Plant. 2012 Nov;5(6):1375-88. doi: 10.1093/mp/sss080. Epub 2012 Aug 28.
Drought is one of the most serious environmental factors that limit the productivity of agricultural crops worldwide. However, the mechanism underlying drought tolerance in plants is unclear. WRKY transcription factors are known to function in adaptation to abiotic stresses. By screening a pool of WRKY-associated T-DNA insertion mutants, we isolated a gain-of-function mutant, acquired drought tolerance (adt), showing improved drought tolerance. Under drought stress conditions, adt accumulated higher levels of ABA than wild-type plants. Stomatal aperture analysis indicated that adt was more sensitive to ABA than wild-type plants. Molecular genetic analysis revealed that a T-DNA insertion in adt led to activated expression of a WRKY gene that encodes the WRKR57 protein. Constitutive expression of WRKY57 also conferred similar drought tolerance. Consistently with the high ABA content and enhanced drought tolerance, three stress-responsive genes (RD29A, NCED3, and ABA3) were up-regulated in adt. ChIP assays demonstrated that WRKY57 can directly bind the W-box of RD29A and NCED3 promoter sequences. In addition, during ABA treatment, seed germination and early seedling growth of adt were inhibited, whereas, under high osmotic conditions, adt showed a higher seed germination frequency. In summary, our results suggested that the activated expression of WRKY57 improved drought tolerance of Arabidopsis by elevation of ABA levels. Establishment of the functions of WRKY57 will enable improvement of plant drought tolerance through gene manipulation approaches.
干旱是全球范围内限制农业作物生产力的最严重环境因素之一。然而，植物耐旱性的机制尚不清楚。WRKY 转录因子已知在适应非生物胁迫中发挥作用。通过筛选一组 WRKY 相关的 T-DNA 插入突变体，我们分离到一个功能获得型突变体，获得耐旱性（adt），表现出增强的耐旱性。在干旱胁迫条件下，adt 积累的 ABA 水平高于野生型植物。气孔孔径分析表明，adt 比野生型植物对 ABA 更敏感。分子遗传分析表明，adt 中的 T-DNA 插入导致 WRKY 基因的激活表达，该基因编码 WRKR57 蛋白。WRKY57 的组成型表达也赋予了类似的耐旱性。与高 ABA 含量和增强的耐旱性一致，三个应激响应基因（RD29A、NCED3 和 ABA3）在 adt 中上调。ChIP 实验表明，WRKY57 可以直接结合 RD29A 和 NCED3 启动子序列的 W-box。此外，在 ABA 处理下，adt 的种子萌发和早期幼苗生长受到抑制，而在高渗条件下，adt 的种子萌发频率更高。总之，我们的结果表明，WRKY57 的激活表达通过提高 ABA 水平来提高拟南芥的耐旱性。WRKY57 功能的确立将通过基因操作方法提高植物的耐旱性。
