a Department of Plant Biology , Cornell University , Ithaca , NY , USA.
Plant Signal Behav. 2017 Jun 3;12(6):e1331197. doi: 10.1080/15592324.2017.1331197. Epub 2017 May 23.
Plastoglobules (PGs) in chloroplasts are monolayer lipid-protein particles attached to thylakoids. The size and number of PGs per chloroplast respond dynamically to abiotic environmental stresses and developmental transitions. During senescence, the thylakoid membranes and its constituents are dismantled in controlled fashion. Leaf senescence coincides with a dramatic increase in the size of PGs, which is consistent with a functional role of PG in remobilization of thylakoid membrane components. In a recent publication, we showed that PG-localized metallopeptidase PGM48 promotes natural senescence. In plants, PGM48 has homologs in mitochondria and the endomembrane system, but PGM48 evolved specifically in photosynthetic organisms. Extensive analysis of Arabidopsis transgenic lines either under- or overexpressing PGM48, showed that PGM48 is a positive regulator of senescence, and we proposed that PG-localized carotenoid cleavage enzyme 4 (CCD4) is a potential substrate of PGM48. Here, we discuss PGM48 function and how it may accelerate natural senescence.
质体小球（PGs）是附着在类囊体上的单层脂蛋白颗粒。每个叶绿体中 PG 的大小和数量对非生物环境胁迫和发育转变有动态响应。在衰老过程中，类囊体膜及其组成部分以受控的方式被拆除。叶片衰老与 PG 大小的显著增加相一致，这与 PG 在类囊体膜成分再动员中的功能作用一致。在最近的一篇出版物中，我们表明，定位于 PG 的金属肽酶 PGM48 促进了自然衰老。在植物中，PGM48 在线粒体和内质网系统中有同源物，但 PGM48 是在光合生物中特异性进化而来的。对过表达或低表达 PGM48 的拟南芥转基因系进行的广泛分析表明，PGM48 是衰老的正调节剂，我们提出定位于 PG 的类胡萝卜素裂解酶 4（CCD4）可能是 PGM48 的潜在底物。在这里，我们讨论了 PGM48 的功能以及它如何加速自然衰老。
