Analytical study on the importance and the mechanism of chloroplast photorelocation movement

植物叶绿体回避反应的重要性。利用叶绿体回避运动缺陷的不同类型的突变体phot2和chup1，我们发现这些突变体比野生型植物更容易在强光下受到坏死损伤。我们得出结论，叶绿体回避运动实际上减少了叶绿体对光的吸收，因此可能对植物在自然生长条件下的生存起重要作用。光敏色素3在蕨类植物中的作用。在一些蕨类植物中，趋光性和叶绿体光定位受红光和蓝光控制，但光感受器尚未确定。我们发现光敏色素3 （phy3）是光敏色素和趋光素的嵌合体，具有红光诱导的向光性和叶绿体光定位的功能。由于phy3极大地增强了定向叶片和叶绿体对白光的敏感性，这种嵌合光感受器可能在低光冠层条件下蕨类植物的分化和繁殖中发挥了关键作用。CHUP1功能用于细胞器定位和运动。CHUP1编码一种包含多个结构域的蛋白质，如肌动蛋白结合结构域和脯氨酸丰富区域。在叶片细胞中表达的CHUP1与GFP融合蛋白靶向叶绿体外包膜，表明CHUP1定位于叶绿体。CHUP1在体外与F-actin结合。因此，CHUP1被确定为植物细胞中细胞器定位和运动所需的蛋白质。PHOT2的功能域。通过瞬时表达非突变体AcPHOT2 cDNA，可以恢复该蕨类植物叶绿体的避避运动，表明该植物的避避运动是由AcPHOT2蛋白介导的。Acphot2蛋白的进一步功能分析使用这种叶绿体避免运动的瞬时实验进行。结果表明，Acphot2的LOV2结构域对回避运动至关重要，而不是LOV1结构域。少

Importance of chloroplast avoidance response in plants.Using different classes of mutant, phot2 and chup1, defective in chloroplast avoidance movement, we show that these mutants are more susceptible to necrotic damage in high light than wild-type plants. We conclude that chloroplast avoidance movement actually reduces the amount of light absorption by chloroplasts, and might thus play an important role in the survival of plants under natural growth conditions.Function of phytochrome 3 in ferns.In some ferns, phototropism and chloroplast photorelocation are controlled by red light as well as blue light, but the photoreceptor had not been identified. We identify a function of phytochrome 3 (phy3), a chimera of phytochrome and phototropin, both for red light-induced phototropism and chloroplast photorelocation. Since phy3 greatly enhances the sensitivity to white light in orienting leaves and chloroplasts, this chimeric photoreceptor may have played a key role in the divergence and proli … More feration of fern species under low-light canopy conditions.CHUP1 function for organellar positioning and movement.CHUP1 encodes a protein containing multiple domains, such as an actin-binding domain and a proline-rich region. The fusion protein of CHUP1 and GFP expressed in leaf cells was targeted to the outer envelope of chloroplasts, suggesting CHUP1 localization in chloroplasts. CHUP1 was found to bind F-actin in vitro. CHUP1 is thus identified as a protein required for organellar positioning and movement in plant cells.Functional domain of PHOT2.The avoidance movement in Adiantum phot2 mutants could be restored by transient expression of non-mutant AcPHOT2 cDNA, indicating that the chloroplast avoidance movement in this fern is mediated by the Acphot2 protein. Further functional analyses of the Acphot2 protein were performed using this transient assay for chloroplast avoidance movement. The results obtained suggest that the LOV2, but not the LOV1, domain of Acphot2 is essential for avoidance movement. Less