Izumi Masanori, Nakamura Sakuya, Li Nan
Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan.
Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
Front Plant Sci. 2019 Mar 22;10:280. doi: 10.3389/fpls.2019.00280. eCollection 2019.
Photosynthetic reactions in chloroplasts convert atmospheric carbon dioxide into starch and soluble sugars during the day. Starch, a transient storage form of sugar, is broken down into sugars as a source for respiratory energy production at night. Chloroplasts thus serve as the main sites of sugar production for photoautotrophic plant growth. Autophagy is an evolutionarily conserved intracellular process in eukaryotes that degrades organelles and proteins. Numerous studies have shown that autophagy is actively induced in sugar-starved plants. When photosynthetic sugar production is inhibited by environmental cues, chloroplasts themselves may become an attractive alternative energy source to sugars their degradation. Here, we summarize the process of autophagic turnover of chloroplasts and its roles in plants in response to sugar starvation. We hypothesize that piecemeal-type chloroplast autophagy is specifically activated in plants in response to sugar starvation.
白天，叶绿体中的光合作用反应将大气中的二氧化碳转化为淀粉和可溶性糖。淀粉是糖的一种临时储存形式，在夜间被分解为糖，作为呼吸能量产生的来源。因此，叶绿体是光自养植物生长过程中糖产生的主要场所。自噬是真核生物中一种进化上保守的细胞内过程，可降解细胞器和蛋白质。大量研究表明，在糖饥饿的植物中自噬被积极诱导。当光合糖的产生受到环境因素抑制时，叶绿体本身可能成为糖降解的一种有吸引力的替代能源。在这里，我们总结了叶绿体自噬周转的过程及其在植物中对糖饥饿的响应作用。我们假设，在植物中，响应糖饥饿时，逐步型叶绿体自噬会被特异性激活。
