Functional Analyses of the Activation Loop of Phototropin2 in Arabidopsis
Functional Analyses of the Activation Loop of Phototropin2 in Arabidopsis
复制标题
DOI：
10.1104/pp.111.175943
复制
发表时间：
2011-05-01
期刊：
影响因子：
7.4
通讯作者：
Shimazaki, Ken-ichiro
中科院分区：
文献类型：
--
作者：
Inoue, Shin-ichiro;Matsushita, Tomonao;Shimazaki, Ken-ichiro
向光蛋白（phot 1和phot 2）是自磷酸化蓝光受体激酶，介导蓝光反应，如向光性，叶绿体积累，和气孔开放在拟南芥（拟南芥）。在强蓝光下，只有phot 2诱导叶绿体回避反应。phot 1中激酶激活环的丝氨酸（Ser）残基被蓝光自磷酸化，自磷酸化对于phot 1介导的反应是必不可少的。然而，phot 2中自磷酸化的作用仍有待确定。在这项研究中，我们取代丝氨酸761和丝氨酸763与丙氨酸（S761 A-S763 A）的phot 2激活环的保守残基，并通过调查phot 2介导的反应后，与此突变体phot 2基因转化phot 1 phot 2双突变体分析其功能。表达突变体phot 2蛋白的转基因植物表现出受损的反应，叶绿体运动，气孔开放，向光弯曲，叶片展平，和植物生长;和那些表达phot 2与S761 D-S763 D突变显示正常的反应。在phot 2中用丙氨酸取代Ser-761和Ser-763对植物中的激酶活性没有显著影响。从这些结果中，我们得出结论，丝氨酸-761和丝氨酸-763的磷酸化激活环可能是一个共同的主要步骤phot 2介导的反应。
Phototropins (phot1 and phot2) are autophosphorylating blue-light receptor kinases that mediate blue-light responses such as phototropism, chloroplast accumulation, and stomatal opening in Arabidopsis (Arabidopsis thaliana). Only phot2 induces the chloroplast avoidance response under strong blue light. The serine (Ser) residues of the kinase activation loop in phot1 are autophosphorylated by blue light, and autophosphorylation is essential for the phot1-mediated responses. However, the role of autophosphorylation in phot2 remains to be determined. In this study, we substituted the conserved residues of Ser-761 and Ser-763 with alanine (S761A S763A) in the phot2 activation loop and analyzed their function by investigating the phot2-mediated responses after the transformation of phot1 phot2 double mutant with this mutant phot2 gene. Transgenic plants expressing the mutant phot2 protein exhibited impaired responses in chloroplast movement, stomatal opening, phototropic bending, leaf flattening, and plant growth; and those expressing phot2 with S761D S763D mutations showed the normal responses. Substitution of both Ser-761 and Ser-763 with alanine in phot2 did not significantly affect the kinase activity in planta. From these results, we conclude that phosphorylation of Ser-761 and Ser-763 in the activation loop may be a common primary step for phot2-mediated responses.