Inada Sayaka, Ohgishi Maki, Mayama Tomoko, Okada Kiyotaka, Sakai Tatsuya
RIKEN Plant Science Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
Plant Cell. 2004 Apr;16(4):887-96. doi: 10.1105/tpc.019901. Epub 2004 Mar 18.
Phototropin 1 (phot1) and phot2, which are blue light receptor kinases, function in blue light-induced hypocotyl phototropism, chloroplast relocation, and stomatal opening in Arabidopsis (Arabidopsis thaliana). Previous studies have shown that the proteins RPT2 (for ROOT PHOTOTROPISM2) and NPH3 (for NONPHOTOTROPIC HYPOCOTYL3) transduce signals downstream of phototropins to induce the phototropic response. However, the involvement of RPT2 and NPH3 in stomatal opening and in chloroplast relocation mediated by phot1 and phot2 was unknown. Genetic analysis of the rpt2 mutant and of a series of double mutants indicates that RPT2 is involved in the phot1-induced phototropic response and stomatal opening but not in chloroplast relocation or phot2-induced movements. Biochemical analyses indicate that RPT2 is purified in the crude microsomal fraction, as well as phot1 and NPH3, and that RPT2 makes a complex with phot1 in vivo. On the other hand, NPH3 is not necessary for stomatal opening or chloroplast relocation. Thus, these results suggest that phot1 and phot2 choose different signal transducers to induce three responses: phototropic response of hypocotyl, stomatal opening, and chloroplast relocation.
向光素1（phot1）和向光素2是蓝光受体激酶，在拟南芥中参与蓝光诱导的下胚轴向光性、叶绿体重新定位和气孔开放过程。先前的研究表明，RPT2（ROOT PHOTOTROPISM2）蛋白和NPH3（NONPHOTOTROPIC HYPOCOTYL3）蛋白在向光素下游转导信号以诱导向光性反应。然而，RPT2和NPH3是否参与由phot1和phot2介导的气孔开放和叶绿体重新定位尚不清楚。对rpt2突变体和一系列双突变体的遗传分析表明，RPT2参与由phot1诱导的向光性反应和气孔开放，但不参与叶绿体重新定位或由phot2诱导的运动。生化分析表明，RPT2与phot1和NPH3一样，在粗微粒体组分中被纯化，并且RPT2在体内与phot1形成复合物。另一方面，NPH3对于气孔开放或叶绿体重新定位不是必需的。因此，这些结果表明，phot1和phot2选择不同的信号转导因子来诱导三种反应：下胚轴向光性反应、气孔开放和叶绿体重新定位。
