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Dynamics of protein and polar lipid recruitment during lipid droplet assembly in Chlamydomonas reinhardtii
Author(s) -
Tsai ChiaHong,
Zienkiewicz Krzysztof,
Amstutz Cynthia L.,
Brink Benedikt G.,
Warakat Jaruswan,
Roston Rebecca,
Benning Christoph
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12917
Subject(s) - chlamydomonas reinhardtii , chloroplast , lipid droplet , chlamydomonas , biogenesis , chloroplast membrane , biology , microbiology and biotechnology , biochemistry , membrane , cytosol , biophysics , thylakoid , gene , mutant , enzyme
Summary In plants, neutral lipids are frequently synthesized and stored in seed tissues, where the assembly of lipid droplets ( LD s) coincides with the accumulation of triacylglycerols ( TAG s). In addition, photosynthetic, vegetative cells can form cytosolic LD s and much less information is known about the makeup and biogenesis of these LD s. Here we focus on Chlamydomonas reinhardtii as a reference model for LD s in a photosynthetic cell, because in this unicellular green alga LD dynamics can be readily manipulated by nitrogen availability. Nitrogen deprivation leads to cellular quiescence during which cell divisions cease and TAG s accumulate. The major lipid droplet protein ( MLDP ) forms a proteinaceous coat surrounding mature LD s. Reducing the amount of MLDP affects LD size and number, TAG breakdown and timely progression out of cellular quiescence following nitrogen resupply. Depending on nitrogen availability, MLDP recruits different proteins to LD s, tubulins in particular. Conversely, depolymerization of microtubules drastically alters the association of MLDP with LD s. LD s also contain select chloroplast envelope membrane proteins hinting at an origin of LD s, at least in part, from chloroplast membranes. Moreover, LD surface lipids are rich in de novo synthesized fatty acids, and are mainly composed of galactolipids which are typical components of chloroplast membranes. The composition of the LD membrane is altered in the absence of MLDP . Collectively, our results suggest a mechanism for LD formation in C. reinhardtii involving chloroplast envelope membranes by which specific proteins are recruited to LD s and a specialized polar lipid monolayer surrounding the LD is formed.