Analyses on the dichroic phytochrome regulating phototropism and photorelocation of chloroplasts in ferns and mosses

在蕨类植物和包括苔藓在内的其他低等植物中，许多光反应都受到二色性光敏色素分子的调节。在本工作中，我旨在阐明二向色性光敏色素分子，并分析其向光性和细胞内叶绿体光位移的调控过程。获得的结果如下：1)二色光敏色素介导的苔藓叶绿体重定位运动：与蕨类原丝藻的情况一样，首次发现二色光敏色素和二色蓝光受体共同调控着光敏原生苔藓细胞的叶绿体光重定位运动。对使用细胞骨架抑制剂的运动系统的进一步分析表明，光敏色素反应仅使用微管作为轨迹，而蓝光响应同时使用微管和肌动蛋白微丝系统。光感受器对运动系统的不同调控以前从未见过报道，这与蕨类植物的情况形成了很好的对比，在蕨类植物中，两个光受体都调节微丝系统而不是微管系统。2)光敏素对蕨类植物二色性光敏色素的基因破坏：通过将二色性光敏色素候选基因PHY3的中断结构引入原丝状体细胞，我们获得了一株缺乏光敏性和受光敏色素调控的叶绿体光定位的菌株。该菌株仍保留蓝光诱导的反应。3)过表达蕨类植物PHY3基因的分析：将蕨类植物PHY3基因导入苔藓细胞，并由35S启动子调控。但对红光诱导的向光性或叶绿体移位没有影响。4)二色性光敏色素定向改变突变株的分离：对二色性光敏色素胞内定位缺陷的突变株进行了筛选，但到目前为止还没有得到菌株。

Many photoresponses are regulated by dichroic phytochrome molecules in ferns and other lower plants including mosses. In the present work, I aimed to elucidate the dichroic phytochrome molecule and to analyze its regulatory processes of phototropism and intracellular chloroplast photorelocation. Results obtained are as follows.1)Dichroic phytochrome-mediate chloroplast relocation movement in the moss, Physcomitrella patens : As in the case of fern protonemata, chloroplast photorelocation movement in Physcomitrella protonemal cells was shown, for the first time, to be regulated by dichroic phytochrome as well as by dichroic blue light receptor. Further analyses on the motile system using cytoskeletal inhibitors revealed that phytochrome responses utilize only microtubules as tracks while blue light responses use both microtubule and actin microfilament systems. The differential regulation of motile systems by photoreceptors has never been reported before and well contrasts with case of fern, where both photoreceptors regulate microfilament system but not microtubule system.2)Gene disruption of dichroic phytochrome in the fern Adiantum capillus-veneris : By introducing a disruption construct of PHY3, a candidate of dichroic phytochrome gene to a protonemal cell, we obtained a strain which lacks both phototropism and chloroplast photorelocation regulated by phytochrome. The strain still retained the blue light-induced responses. Detailed analyses are still on the way.3)Analyses on the Physcomitrella cells over-expressing fern PHY3 gene : Fern PHY3 gene was introduced and over-driven by 35S promoter in the moss cells. However, no effect on the red light-induced phototropism or chloroplast relocation movement was observed.4)Isolation of Adiantum mutant altered in the orientation of dichroic phytochrome : Screening of mutants which are defective in the intracellular orientation of dichroic phytochrome are performed, but so far, no strains are obtained.