(600-09) Endoplasmic reticulum–chloroplast contact in phospholipid metabolism mediated by a pair of differentially localized lipid phosphate phosphatases in Arabidopsis
Postdoctoral Fellow RIKEN Center for Sustainable Resource Science Yokohama, Kanagawa, Japan
Body of Abstract: In plants, cellular membrane lipids are synthesized mainly in the plastids and endoplasmic reticulum (ER). However, the inter-organelle communication mechanism in the lipid biosynthesis is largely open to investigation. In this study, we explore a pair of uncharacterized lipid phosphate phosphatase (LPP) isoforms in Arabidopsisthaliana with differential subcellular localization that functionally cooperate in ER glycerolipid metabolism. The LPP pair, which catalyzes the conversion of phosphatidic acid (PA) to diacylglycerol (DAG) in glycerolipid metabolism, were differentially localized at ER and chloroplasts despite their similar tissue expression pattern. Genetic suppression of these LPPs affected male gametogenesis in reproductive organs and ER phospholipid biosynthesis, which indicates their functional redundancy. Of note, this pathway was predominant in seed, where major lipid flux goes toward triacylglycerol (TAG) accumulation following phospholipid metabolism. Overexpression of either isoform increased seed TAG, suggesting that this association may be functionally relevant. We suggest that ER glycerolipid metabolism may require a chloroplast-localized enzyme, representing the importance of inter-organelle communication in membrane lipid homeostasis.