叶绿素酶催化的叶绿素脱植基反应对番茄果实类胡萝卜素合成的影响

叶绿素降解是叶片衰老和果实成熟时的明显迹象之一。叶片中叶绿素降解的研究已较为透彻，脱镁叶绿素酶（PPH）而非叶绿素酶（CLH）是叶绿素脱植基的关键酶，但果实中叶绿素降解途径还不清楚。PPH沉默的番茄植株叶片完全滞绿而果实叶绿素部分降解，暗示其他基因也参与果实叶绿素的降解。我们前期研究发现CLH和PPH分别在果实后熟的第3天和6天时表达量达到高峰；在PPH功能丧失的gf1和gf2突变体果实中类胡萝卜素含量高于野生型番茄。我们推测CLH和PPH都参与了果实叶绿素的降解，果实中有色体的形成和类胡萝卜素的积累依赖于CLH参与的叶绿素脱植基反应。本项目从分子生物学、代谢途径以及遗传学角度明确CLH在番茄果实叶绿素降解中的关键作用，并探讨CLH催化的脱植基反应对有色体形成及类胡萝卜素积累的影响。研究成果可拓宽人们对果实叶绿素降解过程的认识，有利于人们从一个新的角度理解果实成熟过程中CLH的生物学功能。

Chlorophyll degradation is one of the most obvious signs of leaf senescence and fruit maturation. The research of chlorophyll degradation in leaf senescence has been thorough studied. It is the pheophytinase not the chlorophyllase is the key enzyme involved in chlorophyll degradation during leaf senescence; however, the chlorophyll degradation in fruit ripening is still not clear. In the PPH silenced plant, the chlorophyll was found completely and partially remained in tomato leaves and fruit during the course of leaves senescence or fruit ripening. The expression of chlorophyllase and pheophytinase reached the peak at 3 and 6 day during the wild type and mutant fruits, respectively. The content of carotenoid in the mutant which lack of the function of PPH were higher than that in wild type tomato. Therefore, we hypothesize that chlorophyllase and pheophytinase involve the chlorophyll degradation at the early and late stage during fruit ripening, and the chlorophyll metabolism catalyzed by chlorophyllase might be related to chromophore formation and carotenoid synthesis. This project view to identify the key role of chlorophyllase on chlorophyll degradation and analyze the effect of the chlorophyllide on chromophore formation and carotenoid accumulation through the methods of molecular biology, metabolism and genetics. The research results can broaden our understanding on chlorophyll degradation and help people to understand the biological function of CLH in fruit ripening from a new perspective.