Analysis of phototropin family signal pathway in chloroplast relocation movement

趋光素家族是叶绿体回避和积累运动、向光性和叶片扁平的光感受器。在拟南芥中，趋光素由两个LOV结构域和激酶组成。羊草中含有两个趋光素基因和一个独特的趋光素基因NEO1。NEO1的C末端与光敏素的全长序列有很高的同源性，尽管N端的前1/3类似于光敏色素的光吸收结构域。为了了解光敏蛋白在拟南芥中的功能，我们研究了光积累水平是否影响光敏蛋白调节的BL反应，包括叶绿体回避运动。回避速度随着光2-GFP融合蛋白的积累或照射剂量的增加而增加。这些结果表明，不仅在正常情况下，光信号通路的数量足够多，而且信号通路中的成分也已经充分积累。与叶绿体回避运动一样，光调节的向光性也被发现依赖于光2的积累。而P2G积累量小于光合量WT的转基因品系为叶片饱和扁平化水平。因此，新色素1的光敏色素光吸收区域表现出典型的红/远红光可逆性和PFR形式的暗回复，半衰期约为30min。光敏色素3的整个光敏区，包括光敏色素光吸收区和LOV结构域，表现出光可逆性，光敏色素的光转化不受LOV结构域的影响。尽管蓝光照射诱导了LOV结构域的光漂白和PFR的形成，但LOV结构域对PFR的形成没有贡献。这些结果表明，光敏色素的光吸收区域和LOV结构域对于光吸收是独立的。

Phototropin family is a photoreceptor for chloroplast avoidance and accumulation movement, phototropism and leaf flatting. In Arabidopsis, the phototropin consist with two LOV domain and kinase. In fern Adinatum capilus-veneris has two phototropin genes and unique phototropin gene, NEO1. The C-terminus of NEO1 shares high homology with the full length sequence of the phototropin, although the first third of the N-terminus is similar to the light-absorbing domain of phytochrome.To understand phot2 function in Arabidopsis, we examined whether phot2 accumulation levels affect phototropin-regulated BL responses including chloroplast avoidance movement. The avoidance velocity increased with the accumulation of more phot2-GFP fusion protein or with a rise in the fluence rate of irradiation. These results suggest that not only is the amount of phot2 normally enough but also the components of the signaling pathway have accumulated sufficiently. As with the chloroplast avoidance movement, phot2-regulated phototropism was also found to have a dependency on phot2 accumulation. However, the transgenic lines that showed P2G accumulation less than phot2 amounts of WT were saturated flatten level of leaves. Therefore, it is unknown that leaf flattening was dependent on phot2 amounts.The phytochrome-light-absorbing region of neochrome 1 with phytochromobilin showed typical red/far-red light photoreversibility and dark reversion of the Pfr form with a half life of about 30 min. The entire photosensory region of phytochrome 3, which consists of the phytochrome-light-absorbing region and the LOV domains showed photoreversibility and the phytochrome photoconversion was not affected by the LOV domains. Though blue light irradiation induced photobleaching of the LOV domains and Pfr formation, the LOV domains did not contribute to Pfr formation. These results indicate that the phytochrome light-absorbing region and LOV domains are independent for light absorption.