Zheng Hui, Torres-Montilla Salvador, Huang Xingqi, Rodríguez-Concepción Manuel, Lu Shan
Stake Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210023, China.
Institute for Plant Molecular and Cell Biology (IBMCP), CSIC-Universitat Politècnica de València, Valencia 46022, Spain.
Plant Physiol. 2025 May 30;198(2). doi: 10.1093/plphys/kiaf242.
The transition of chloroplasts into chromoplasts and gerontoplasts during fruit ripening and leaf senescence, respectively, involves chlorophyll breakdown and chloroplast deterioration. Chlorophyll removal is carried out by several enzymes. Among them, the Mg-dechelatase STAY-GREEN (SGR) catalyzes the first step of chlorophyll degradation. The tomato green-flesh (gf) and pepper chlorophyll retainer (cl) mutants are SGR loss-of-function mutants that maintain high levels of thylakoid structures during chromoplast development in ripening fruits. Here, by overexpressing SGR in nonilluminated Nicotiana benthamiana leaves, we demonstrated that SGR triggers the onset of chloroplast deterioration, resulting in the formation of orange-leaf sectors containing plastids with carotenoid-bearing structures, although carotenoid production is not induced. Metabolite, microscopy, and transcriptome analyses suggested the onset of chloroplast senescence, indicating a possible transitional plastid stage in SGR-overexpressing regions. Overall, our work demonstrates the remarkable ability of plant plastids to adapt their ultrastructure to accommodate the precise metabolic composition of various developmental and environmental contexts.
在果实成熟和叶片衰老过程中，叶绿体分别向有色体和老年质体的转变涉及叶绿素降解和叶绿体退化。叶绿素的去除由几种酶完成。其中，镁脱螯合酶保持绿色（SGR）催化叶绿素降解的第一步。番茄绿果肉（gf）和辣椒叶绿素保留（cl）突变体是SGR功能缺失突变体，在成熟果实的有色体发育过程中维持高水平的类囊体结构。在这里，通过在未光照的本氏烟草叶片中过表达SGR，我们证明SGR触发叶绿体退化的开始，导致形成含有具有类胡萝卜素结构的质体的橙色叶区，尽管类胡萝卜素的产生未被诱导。代谢物、显微镜和转录组分析表明叶绿体衰老开始，表明在SGR过表达区域可能存在过渡质体阶段。总体而言，我们的工作证明了植物质体具有显著能力来调整其超微结构，以适应各种发育和环境背景下的精确代谢组成。
