Naslov
The Plastoglobule-Localized Metallopeptidase PGM48 is a Positive Regulator of Senescence in Arabidopsis thaliana

Autori
Bhuiyan, Nazmul H. ; Friso, Giulia ; Rowland, Elden ; Majsec, Kristina ; van Wijk, Klaas J.

Izvornik
The Plant cell (1040-4651) 28 (2016); 3020-3037

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Radovi u časopisima, članak, znanstveni

Ključne riječi
plastoglobule, m48 metallopeptidase, senescence

Sažetak
Plastoglobuli (PG) are thylakoid-associated monolayer lipid particles with a specific proteome of ~30 PG core proteins and isoprenoid- and neutral lipids. During senescence, PG 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 ENZYME 4 (CCD4), and significantly increased levels of the senescence-induced ABC1 kinase 7 (ABC1K7) and PHYTYL ESTER SYNTHASE 1 (PES1). Yeast-2-hybrid experiments identified PG core proteins ABC1 KINASE 3, 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.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

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