The Autophagic Degradation of Chloroplasts via Rubisco-Containing Bodies Is Specifically Linked to Leaf Carbon Status But Not Nitrogen Status in Arabidopsis
The Autophagic Degradation of Chloroplasts via Rubisco-Containing Bodies Is Specifically Linked to Leaf Carbon Status But Not Nitrogen Status in Arabidopsis
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DOI：
10.1104/pp.110.158519
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发表时间：
2010-11-01
期刊：
影响因子：
7.4
通讯作者：
Ishida, Hiroyuki
中科院分区：
文献类型：
--
作者：
Izumi, Masanori;Wada, Shinya;Ishida, Hiroyuki
自噬是一种细胞内的过程，促进细胞质成分的液泡降解，并在饥饿期间的营养循环中起重要作用。我们以前证明，叶绿体可以部分动员到液泡自噬通过球状体命名为Rubisco含体（RCBs）。尽管叶绿体含有约80%的叶片总氮，并且是新生长的主要碳和氮来源，但叶片营养状况与RCB产生之间的关系仍不清楚。我们研究了营养因子对表达基质靶向荧光蛋白的转基因拟南芥（Arabidopsis thaliana）叶片中RCB外观的影响。在离体叶片中，RCBs的出现受到代谢糖的抑制，这些糖是外部添加的或在光合作用过程中产生的。光合作用的抑制缓解了光介导的抑制。在一个昼夜循环，RCB生产抑制在一天结束时切除的叶片淀粉含量高。无淀粉突变体磷酸葡萄糖变位酶和ADP-Glc焦磷酸化酶1产生大量的RCB，而淀粉过量突变体淀粉过量1和麦芽糖过量1产生较少的RCB。在氮限制植物中，随着叶片碳水化合物的积累，RCB的产生受到抑制。我们认为自噬过程中叶绿体蛋白质的降解与叶片的碳源而非氮源状况密切相关。我们还发现，非RCB型自噬体的外观不受抑制的光，有点响应于氮在离体叶片，不像RCB。这些结果表明，叶绿体蛋白质的降解通过RCBs是专门控制自噬。
Autophagy is an intracellular process facilitating the vacuolar degradation of cytoplasmic components and is important for nutrient recycling during starvation. We previously demonstrated that chloroplasts can be partially mobilized to the vacuole by autophagy via spherical bodies named Rubisco-containing bodies (RCBs). Although chloroplasts contain approximately 80% of total leaf nitrogen and represent a major carbon and nitrogen source for new growth, the relationship between leaf nutrient status and RCB production remains unclear. We examined the effects of nutrient factors on the appearance of RCBs in leaves of transgenic Arabidopsis (Arabidopsis thaliana) expressing stroma-targeted fluorescent proteins. In excised leaves, the appearance of RCBs was suppressed by the presence of metabolic sugars, which were added externally or were produced during photosynthesis in the light. The light-mediated suppression was relieved by the inhibition of photosynthesis. During a diurnal cycle, RCB production was suppressed in leaves excised at the end of the day with high starch content. Starchless mutants phosphoglucomutase and ADP-Glc pyrophosphorylase1 produced a large number of RCBs, while starch-excess mutants starch-excess1 and maltose-excess1 produced fewer RCBs. In nitrogen-limited plants, as leaf carbohydrates were accumulated, RCB production was suppressed. We propose that there exists a close relationship between the degradation of chloroplast proteins via RCBs and leaf carbon but not nitrogen status in autophagy. We also found that the appearance of non-RCB-type autophagic bodies was not suppressed in the light and somewhat responded to nitrogen in excised leaves, unlike RCBs. These results imply that the degradation of chloroplast proteins via RCBs is specifically controlled in autophagy.