Lou Dengji, Wang Houping, Liang Gang, Yu Diqiu
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of SciencesKunming, China.
College of Life Sciences, University of Chinese Academy of SciencesBeijing, China.
Front Plant Sci. 2017 Jun 13;8:993. doi: 10.3389/fpls.2017.00993. eCollection 2017.
SNF 1-RELATED PROTEIN KINASE 2 (SnRK2) is a family of plant-specific protein kinases which is the key regulator of hyper-osmotic stress signaling and abscisic acid (ABA)-dependent development in various plants. Among the rice subclass-I and -II SnRK2s, osmotic stress/ABA-activated protein kinase 2 (SAPK2) may be the primary mediator of ABA signaling. However, SAPK2 has not been comprehensively characterized. In this study, we elucidated the functional properties of SAPK2 using loss-of-function mutants produced with the CRISPR/Cas9 system. The expression level was strongly upregulated by drought, high-salinity, and polyethylene glycol (PEG) treatments. The mutants exhibited an ABA-insensitive phenotype during the germination and post-germination stages, suggesting that SAPK2 had a pivotal role related to ABA-mediated seed dormancy. The mutants were more sensitive to drought stress and reactive oxygen species (ROS) than the wild-type plants, indicating that SAPK2 was important for responses to drought conditions in rice. An additional investigation revealed that SAPK2 increased drought tolerance in the following two ways: (i) by reducing water loss the accumulation of compatible solutes, promoting stomatal closure, and upregulating the expression levels of stress-response genes such as , , , , and slow anion channel (SLAC)-associated genes such as and ; (ii) by inducing the expression of antioxidant enzyme genes to promote ROS-scavenging abilities that will ultimately decrease ROS damages. Moreover, we also observed that SAPK2 significantly increased the tolerance of rice plants to salt and PEG stresses. These findings imply that SAPK2 is a potential candidate gene for future crop improvement studies.
蔗糖非发酵-1-相关蛋白激酶2（SnRK2）是一类植物特有的蛋白激酶家族，是多种植物中高渗胁迫信号传导和脱落酸（ABA）依赖性发育的关键调节因子。在水稻I类和II类SnRK2中，渗透胁迫/ABA激活蛋白激酶2（SAPK2）可能是ABA信号传导的主要介质。然而，SAPK2尚未得到全面表征。在本研究中，我们使用CRISPR/Cas9系统产生的功能缺失突变体阐明了SAPK2的功能特性。干旱、高盐和聚乙二醇（PEG）处理强烈上调了其表达水平。突变体在萌发和萌发后阶段表现出ABA不敏感表型，表明SAPK2在ABA介导的种子休眠中起关键作用。突变体比野生型植物对干旱胁迫和活性氧（ROS）更敏感，表明SAPK2对水稻干旱条件的响应很重要。进一步研究表明，SAPK2通过以下两种方式提高耐旱性：（i）通过减少水分流失、积累相容性溶质、促进气孔关闭以及上调应激反应基因如、、、、和慢阴离子通道（SLAC）相关基因如和的表达水平；（ii）通过诱导抗氧化酶基因的表达来提高ROS清除能力，最终减少ROS损伤。此外，我们还观察到SAPK2显著提高了水稻植株对盐和PEG胁迫的耐受性。这些发现表明，SAPK2是未来作物改良研究的一个潜在候选基因。
