高光效转基因水稻结实率低的机理及优化研究

通过合成生物学和生物工程手段改造光呼吸通路可显著提升光合效率。申请人前期在水稻叶绿体中创建了两条光呼吸支路（GOC和GCGT支路），均显著提高了水稻的光合效率、生物量和产量，但结实率均降低，严重限制了产量的提升潜力，初步的分析结果显示，灌浆后期同化物在茎鞘中显著积累，未能及时转运到籽粒中，受到“流”的限制。本项目拟以GOC和GCGT水稻为材料：①通过多基因转化技术同时导入3个“畅流”关键基因，旨在进一步挖掘GOC和GCGT水稻的增产潜力；②采用验证式策略从细胞学、生理生化和分子水平系统解析高光效转基因水稻结实率低的机理，探求“光呼吸支路=>高光效=>增源=>扩库=>畅流=>超高产”同步协调的新策略，为高光效分子育种提供材料、理论依据和技术支撑。此外，本研究对于解决某些超级杂交稻结实率差的问题也具有指导作用。

Engineering photorespiration by using synthetic biology and biotechnological approaches can significantly increasing photosynthetic efficiency. In the preliminary study, we have successfully introduced two photorespiratory bypasses (GOC and GCGT bypass) into rice chloroplasts. The GOC and GCGT rice showed increased photosynthetic efficiency, biomass and grain yield. However, setting rates are negatively affected both in GOC and GCGT rice, such that their yield-increasing potential have not yet been maximized. Preliminary results showed that sucrose and starch content in stems significantly accumulated in GCGT plants at filling stage, this suggested that photosynthetic carbohydrates in stems were not timely or efficiently transported to grain, which was restricted by the "Flow". Aiming at this problem, we plan to further conduct following studies in this project: (i) by utilizing loxP/cre homologous recombination technology, simultaneously introduce three key genes into GOC and GCGT rice that promoting the assimilates transfer from stems to grains in time; (ii) after obtaining those transgenic rice, using a validated strategy to systematically analyze the mechanism that why the high photosynthetic efficiency transgenic rice has low seed setting rate from cytology, physiology, biochemistry, and molecular levels. We expect to propose a new strategy to further increase grain yield in rice, which is as follows "photorespiratory bypass => high photosynthetic efficiency => increasing “source” => increasing “sink” => expanding “flow” => increasing yield". The final objective of this study is to maximize the yield-increasing potential of GOC and GCGT rice, so as to provide material and technical support for molecular breeding of rice. In addition, this study may also provide guidance for answering some problems about why some super hybrid rice has poor seed setting rate.