拟南芥叶绿体蛋白HPE1参与光合作用调控及其作用机理研究

The improvement of photosynthetic efficiency is very important for plant to promote growth and development. We previously found that two hpe1 mutants show high photosynthetic efficiency, significantly altered components of chlorophyll, higher utilization efficiency of photosynthetic energy, more abundances of photosystem I and photosystem II complex combined with chlorophyll. Moreover, both photosynthetic quantum yield and biomass in hpe1 mutants are increased obviously, indicating HPE1 involves in regulation of photosynthetic efficiency. It is more interesting that, as a new chloroplast protein containing RNA recognition motif (RRM), HPE1 interacts with chloroplast RNA splicing factors CAF1 and OTP51, and affects the splicing of chloroplast introns, suggesting HPE1 may be involved in regulation of photosynthetic efficiency mediated by RNA splicing. The goal of this project is to further study the regulation mechanism mediated by HPE1 in photosynthetic efficiency regulation. First, we will confirm the involvement of HPE1 in photosynthetic efficiency regulation in genetics, and then investigate the splicing efficiency of other chloroplast genes associated with the function of HPE1 in chloroplast RNA splicing. Finally, the association relationship between HPE1 and its target RNA will be analyzed. Collectively, this study will illuminate the role of a novel chloroplast protein HPE1 in chloroplast RNA splicing, and reveal the mechanism of regulation of photosynthesis mediated by chloroplast gene expression in plant growth and development.

光合作用效率的提高对于促进植物生长发育至关重要。我们前期鉴定到高光合效率突变体hpe1：叶绿素组分明显改变,光能利用效率显著提高,并且色素结合的光系统I和光系统II复合物丰度明显增多；更重要的是，hpe1突变体光合产量及生物量明显增加,提示HPE1参与光合效率调控。有趣的是，作为包含RNA识别结构域(RRM)的叶绿体新蛋白，HPE1与已知RNA编辑因子CAF1、OTP51互作，影响叶绿体trnK、atpF、rpoC1等内含子的剪接，提示HPE1可能通过RNA剪接参与光合效率调控，值得深入研究。本项目拟在确证HPE1参与光合效率调控的基础上，结合对叶绿体RNA剪接的影响，进一步探究HPE1对叶绿体基因的剪接机理，包括系统普查叶绿体其他基因剪接效率，并分析与靶基因之间的互作关系。本研究将鉴定一个新的叶绿体RNA剪接因子，并由此揭示植物中由叶绿体基因表达调控介导的光合效率及生长发育调控新机制。

植物光合作用效率的优化对于提高植物生物量及作物产量至关重要。本研究鉴定了一个新的光效调控基因HIGH PHOTOSYNTHETIC EFFICIENCY 1(HPE1)，该光效调控基因缺失后通过优化植物光捕获色素，有效增加了光合作用效率和生物量。较野生型拟南芥相比，hpe1突变体表现出更快的电子传递速率和增加的碳水化合物积累量。HPE1基因编码一个包含RNA识别结构域的叶绿体新蛋白，通过和trnK, rpoC1及atpF等靶标RNA直接结合，参与叶绿体RNA剪接。此外，HPE1与CAF1及OTP51等其他叶绿体剪接因子互作，协同参与叶绿体RNA剪接调控。HPE1缺失可能通过核质信号转导改变了细胞核编码的叶绿素相关基因的表达，从而在一定程度上降低了叶绿素a+b的整体含量，但是增加了叶绿素a/b的比例。有趣的是，这种光捕获色素的调整减小了天线大小，提高了光捕获，降低了光能损失，缓解了光系统损伤，最终增加了光合作用量子产量。综上，该研究鉴定了一个重要的光效调控基因HPE1，并由此揭示了一种通过优化捕光色素来提高高等植物光合作用效率和整体生物量的新策略。相关研究论文以第一作者发表于国际植物学权威期刊Plant Physiology。论文受到广泛关注，不仅是期刊的亮点文章，Plant Physiology杂志将该论文选为2016年度期刊热门话题（Best of 2016：Top Topics in Plant Physiology journal）。此外，该论文还被F1000作为“新发现”进行推荐。值得注意的是，本项目在完成转录后调控因子HPE1参与光效调控相关研究的基础上，又拓展了光效调控相关的功能研究，鉴定到质体基因表达调控因子DG238，通过转录调控影响叶绿体发育和光效调节，相关研究论文以通讯作者发表于Plant Cell & Physiology（期刊亮点论文）和Journal of Plant Biology。