Department of Biology, Faculty of Sciences, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.
Plant Sci. 2013 Mar;201-202:93-7. doi: 10.1016/j.plantsci.2012.11.012. Epub 2012 Dec 7.
Phototropins (phot1 and phot2), blue light-receptor protein kinases in plants, mediate stomatal opening by activating the plasma membrane H(+)-ATPase in guard cells, but the signaling from phototropins to the H(+)-ATPase remains unknown. A recent study concluded that ROOT PHOTOTROPISM2 (RPT2) is involved in the primary step of this process. However, this conclusion is based solely on the determination of stomatal apertures in the epidermis. We investigated the role of RPT2 in blue light-dependent stomatal opening in more detail. We generated double mutants of rpt2 and phototropins (phot1 or phot2) in the Col ecotype background and obtained the typical phenotypes of rpt2 mutants, including the impairment in phototropism. In contrast, neither blue light-dependent H(+) pumping nor blue light-dependent H(+)-ATPase activation in guard cells was affected in the rpt2 mutants of rpt2, phot1 rpt2, and phot2 rpt2. Stomata in these rpt2 mutants opened widely by blue light in both epidermal peels and intact leaves, and no difference in the responses was found between the wild type and the mutants. From these results, we concluded that RPT2 gene disruption does not affect blue light-dependent stomatal opening.
光受体蛋白激酶（phot1 和 phot2）是植物中的蓝光受体蛋白激酶，通过激活保卫细胞中的质膜 H(+) -ATPase 来介导气孔开放，但光受体蛋白向 H(+) -ATPase 的信号传递仍然未知。最近的一项研究得出结论，ROOT PHOTOTROPISM2（RPT2）参与了这一过程的初始步骤。然而，这一结论仅仅是基于对表皮中气孔孔径的测定。我们更详细地研究了 RPT2 在蓝光依赖性气孔开放中的作用。我们在 Col 生态型背景下生成了 rpt2 和光受体蛋白（phot1 或 phot2）的双突变体，并获得了 rpt2 突变体的典型表型，包括向光性受损。相比之下，rpt2 突变体、phot1 rpt2 和 phot2 rpt2 中的蓝光依赖性 H(+)泵和蓝光依赖性 H(+) -ATPase 激活均不受影响。在这些 rpt2 突变体中，蓝光在表皮剥脱和完整叶片中均可使气孔广泛开放，并且在野生型和突变体之间没有发现响应差异。根据这些结果，我们得出结论，RPT2 基因缺失不影响蓝光依赖性气孔开放。
