The Plastoglobule-Localized Metallopeptidase PGM48 Is a Positive Regulator of Senescence in Arabidopsis thaliana
The Plastoglobule-Localized Metallopeptidase PGM48 Is a Positive Regulator of Senescence in Arabidopsis thaliana
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DOI：
10.1105/tpc.16.00745
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发表时间：
2016-12-01
期刊：
影响因子：
11.6
通讯作者：
van Wijk, Klaas J.
中科院分区：
文献类型：
--
作者：
Bhuiyan, Nazmul H.;Friso, Giulia;van Wijk, Klaas J.
质体球 (PG) 是类囊体相关的单层脂质颗粒，具有与 30 种 PG 核心蛋白、类异戊二烯和中性脂质相似的特定蛋白质组。在衰老过程中，PG 的大小会增加，反映了它们在拆除类囊体膜方面的作用。在这里，我们证明了唯一的 PG 定位肽酶 PGM48 正向调节叶片衰老。我们发现PGM48是M48肽酶家族的成员，具有PGM48同源物，形成仅在光合生物中发现的分支（M48D）。与 M48A、B 和 C 进化枝不同，M48D 成员没有跨膜结构域，这与其在 PG 中独特的亚细胞位置一致。体外测定显示锌依赖性蛋白水解活性和疏水性残基上游的底物裂解。 PGM48 的过度表达加速了叶片的自然衰老，而抑制则延迟了衰老。来自 PGM48 过表达系的衰老玫瑰花结的 PG 的定量蛋白质组学显示，类胡萝卜素裂解酶 4 (CCD4) 的水平显着降低，而衰老诱导的 ABC1 KINASE7 (ABC1K7) 和 PHYTYL ESTER SYNTHASE1 (PES1) 的水平显着增加。酵母双杂交实验确定 PG 核心蛋白 ABC1K3、PES1 和 CCD4 是 PGM48 相互作用蛋白，而其他几种 PG 定位蛋白和叶绿素降解酶不相互作用。我们讨论了 PGM48 可能加速衰老过程的机制。
Plastoglobuli (PG) are thylakoid-associated monolayer lipid particles with a specific proteome of similar to 30 PG core proteins and isoprenoid and neutral lipids. During senescence, PGs increase in size, reflecting their role in dismantling thylakoid membranes. Here, we show that the only PG-localized peptidase PGM48 positively regulates leaf senescence. We discovered that PGM48 is a member of the M48 peptidase family with PGM48 homologs, forming a clade (M48D) only found in photosynthetic organisms. Unlike the M48A, B, and C clades, members of M48D have no transmembrane domains, consistent with their unique subcellular location in the PG. In vitro assays showed Zn-dependent proteolytic activity and substrate cleavage upstream of hydrophobic residues. Overexpression of PGM48 accelerated natural leaf senescence, whereas suppression delayed senescence. Quantitative proteomics of PG from senescing rosettes of PGM48 overexpression lines showed a dramatically reduced level of CAROTENOID CLEAVAGE ENZYME4 (CCD4) and significantly increased levels of the senescence-induced ABC1 KINASE7 (ABC1K7) and PHYTYL ESTER SYNTHASE1 (PES1). Yeast two-hybrid experiments identified PG core proteins ABC1K3, PES1, and CCD4 as PGM48 interactors, whereas several other PG-localized proteins and chlorophyll degradation enzymes did not interact. We discuss mechanisms through which PGM48 could possibly accelerate the senescence process.