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

蕨类植物和包括苔藓在内的其他低等植物的许多光反应是由二色性光敏色素分子调节的。本文旨在阐明二色性光敏色素分子，并分析其趋光性和细胞内叶绿体光定位的调控过程。所得结果如下：1)二色性光敏色素介导的青苔（physcomitellla patens）叶绿体光定位运动：与蕨类植物原胞一样，首次发现小立藓原胞的叶绿体光定位运动既受二色性光敏色素调控，也受二色性蓝光受体调控。使用细胞骨架抑制剂对运动系统的进一步分析表明，光敏色素反应仅利用微管作为轨道，而蓝光反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差异调节从未被报道过，这与蕨类植物的情况形成了很好的对比，在蕨类植物中，光感受器都调节微丝系统，但不调节微管系统。2)蕨类植物Adiantum capillus-veneris二色性光敏色素基因的破坏：通过将二色性光敏色素候选基因PHY3的破坏结构引入原体细胞，获得了既缺乏光敏色素调节的趋光性又缺乏叶绿体光定位的菌株。该菌株仍然保留了蓝光诱导的反应。详细的分析仍在进行中。3)小气泡藻细胞过表达蕨类PHY3基因的分析：在苔藓细胞中引入蕨类PHY3基因，并通过35S启动子过度驱动。然而，对红光诱导的趋光性和叶绿体重新定位运动没有影响。4)二色性光敏色素取向改变突变体的分离：对二色性光敏色素胞内取向缺陷突变体进行了筛选，但目前尚未获得菌株。

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.