Adverse environmental conditions such as drought stress greatly limit the growth and production of crops worldwide. In this study, SlGRAS4, a drought stress-responsive GRAS gene from tomato (Solanum lycopersicum) was functionally characterized. Repressing SlGRAS4 (SlGRAS4-RNAi) increased sensitivity to drought stress, whereas overexpressing SlGRAS4 (SlGRAS4-OE) in tomato enhanced tolerance of this stress. Under stress condition SlGRAS4-OE plants accumulated much less ROS than wild-type and SlGRAS4-RNAi plants. Numerous dehydration induced ROS-scavenging genes were upregulated in SlGRAS4-OE plants after drought stress, implying that SlGRAS4 confers drought tolerance by modulating ROS homeostasis. On the other hand, there are several abscisic acid (ABA)-responsive elements in SlGRAS4 promoter, the relative expression of ABA signaling genes including SlPYLs, SlPP2Cs and SlSnRK2s were verified in WT and transgenic plants both under normal and drought stress, the changed drought sensitivity of transgenic plants was mainly caused by SlSnRK2s, the positive regulators of ABA signaling. Our results suggested that SlGRAS4 directly binds to and activates SlSnRK2.4 promoter, belongs to subclass III SnRK2s, which play crucial role in ABA signaling. Protein studies revealed that SlSnRK2.4 interacts with SlAREB1 and SlAREB2, the major downstream transcription factors of ABA-dependent signaling pathway. SlGRAS4 therefore confers drought tolerance may be through SnRK2-AREB pathway.

诸如干旱胁迫等不利的环境条件极大地限制了全球农作物的生长和产量。在这项研究中，SlGRAS4（一种来自番茄（Solanum lycopersicum）的干旱胁迫响应性GRAS基因）的功能进行了表征。抑制SlGRAS4（SlGRAS4-RNAi）增加了对干旱胁迫的敏感性，而在番茄中过表达SlGRAS4（SlGRAS4- OE）增强了对这种胁迫的耐受性。在胁迫条件下，SlGRAS4- OE植物比野生型和SlGRAS4 -RNAi植物积累的ROS少得多。SlGRAS4中许多脱水诱导的ROS清除基因上调干旱胁迫后的-OE植物，这表明SlGRAS4通过调节ROS稳态来赋予抗旱性。另一方面，在SlGRAS4启动子中有几种脱落酸（ABA）响应元件，在正常和干旱胁迫下，干旱和干旱条件下，野生型和转基因植物中包括SlPYLs，SlPP2Cs和SlSnRK2s在内的ABA信号基因的相对表达都得到了验证转基因植物的敏感性主要是由ABA信号转导的正调控因子SlSnRK2s引起的。我们的研究结果表明SlGRAS4直接结合并激活SlSnRK2.4启动子，属于III类SnRK2s，在ABA信号传导中起关键作用。蛋白质研究表明，SlSnRK2.4与ABA依赖性信号传导途径的主要下游转录因子SlAREB1和SlAREB2相互作用。因此，SlGRAS4可能通过SnRK2-AREB途径赋予了耐旱性。