Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
J Biol Chem. 2010 Mar 19;285(12):9190-201. doi: 10.1074/jbc.M109.051938. Epub 2010 Jan 20.
RPK1 (receptor-like protein kinase 1) localizes to the plasma membrane and functions as a regulator of abscisic acid (ABA) signaling in Arabidopsis. In our current study, we investigated the effect of RPK1 disruption and overproduction upon plant responses to drought stress. Transgenic Arabidopsis overexpressing the RPK1 protein showed increased ABA sensitivity in their root growth and stomatal closure and also displayed less transpirational water loss. In contrast, a mutant lacking RPK1 function, rpk1-1, was found to be resistant to ABA during these processes and showed increased water loss. RPK1 overproduction in these transgenic plants thus increased their tolerance to drought stress. We performed microarray analysis of RPK1 transgenic plants and observed enhanced expression of several stress-responsive genes, such as Cor15a, Cor15b, and rd29A, in addition to H(2)O(2)-responsive genes. Consistently, the expression levels of ABA/stress-responsive genes in rpk1-1 had decreased compared with wild type. The results suggest that the overproduction of RPK1 enhances both the ABA and drought stress signaling pathways. Furthermore, the leaves of the rpk1-1 plants exhibit higher sensitivity to oxidative stress upon ABA-pretreatment, whereas transgenic plants overproducing RPK1 manifest increased tolerance to this stress. Our current data suggest therefore that RPK1 overproduction controls reactive oxygen species homeostasis and enhances both water and oxidative stress tolerance in Arabidopsis.
RPK1（受体样蛋白激酶 1）定位于质膜，作为拟南芥脱落酸（ABA）信号的调节剂。在我们当前的研究中，我们研究了 RPK1 缺失和过表达对植物对干旱胁迫反应的影响。过表达 RPK1 蛋白的转基因拟南芥在根生长和气孔关闭方面表现出增加的 ABA 敏感性，并且表现出较少的蒸腾水损失。相比之下，缺乏 RPK1 功能的突变体 rpk1-1 在这些过程中对 ABA 具有抗性并且表现出增加的水损失。因此，这些转基因植物中 RPK1 的过表达增加了它们对干旱胁迫的耐受性。我们对 RPK1 转基因植物进行了微阵列分析，观察到除了 H2O2 响应基因外，几种应激响应基因，如 Cor15a、Cor15b 和 rd29A 的表达增强。此外，与野生型相比，rpk1-1 中 ABA/应激响应基因的表达水平降低。结果表明，RPK1 的过表达增强了 ABA 和干旱胁迫信号通路。此外，ABA 预处理后 rpk1-1 植物的叶片对氧化应激表现出更高的敏感性，而过表达 RPK1 的转基因植物对这种应激表现出更高的耐受性。因此，我们当前的数据表明，RPK1 的过表达控制活性氧物质的动态平衡，并增强拟南芥的水和氧化应激耐受性。
