Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

Authors

Amélie Kelly, Max Planck Institute of Molecular Plant Physiology
Barbara Kalisch, University of Bonn
Georg Hölzl, University of Bonn
Sandra Schulze, Max Planck Institute of Molecular Plant Physiology
Juliane Thiele, Max Planck Institute of Molecular Plant Physiology
Michael Melzer, Leibniz Institute of Plant Genetics and Crop Plant Research
Rebecca L. Roston, University of Nebraska-LincolnFollow
Christoph Benning, Michigan State University
Peter Dörmann, University of Bonn

Date of this Version

2016

Citation

PNAS Early Edition

Comments

Copyright 2016 Kelly et al.

Abstract

Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol

(DGDG)] are the hallmark lipids of photosynthetic

membranes. The galactolipid synthases MGD1 and DGD1

catalyze consecutive galactosyltransfer reactions but localize to the

inner and outer chloroplast envelopes, respectively, necessitating

intermembrane lipid transfer. Here we show that the N-terminal

sequence of DGD1 (NDGD1) is required for galactolipid transfer

between the envelopes. Different diglycosyllipid synthases (DGD1,

DGD2, and Chloroflexus glucosyltransferase) were introduced into

the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions

(NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction

of DGDG synthesis in the outer envelope membrane was

observed only with diglycosyllipid synthase fusion proteins carrying

NDGD1, indicating that NDGD1 enables galactolipid translocation

between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes

and mediates PA-dependent membrane fusion in vitro.

These findings provide a mechanism for the sorting and selective

channeling of lipid precursors between the galactolipid pools of the

two envelope membranes.