Two Abscisic Acid-Responsive Plastid Lipase Genes Involved in Jasmonic Acid Biosynthesis in Arabidopsis thaliana .

Chloroplast membranes with their unique lipid composition are crucial for photosynthesis. Maintenance of the chloroplast membranes requires finely tuned lipid anabolic and catabolic reactions. Despite the presence of a large number of predicted lipid-degrading enzymes in the chloroplasts, their biological functions remain largely unknown. Recently, we described PLASTID LIPASE1 (PLIP1), a plastid phospholipase A1 that contributes to seed oil biosynthesis. The Arabidopsis thaliana genome encodes two putative PLIP1 paralogs, which we designated PLIP2 and PLIP3. PLIP2 and PLIP3 are also present in the chloroplasts, but likely with different subplastid locations. In vitro analysis indicated that both are glycerolipid A1 lipases. In vivo, PLIP2 prefers monogalactosyldiacylglycerol as substrate and PLIP3 phosphatidylglycerol. Overexpression of PLIP2 or PLIP3 severely reduced plant growth and led to accumulation of the bioactive form of jasmonate and related oxylipins. Genetically blocking jasmonate perception restored the growth of the PLIP2/3 -overexpressing plants. The expression of PLIP2 and PLIP3 , but not PLIP1 , was induced by abscisic acid (ABA), and plip1 plip2 plip3 triple mutants exhibited compromised oxylipin biosynthesis in response to ABA. The plip triple mutants also showed hypersensitivity to ABA. We propose that PLIP2 and PLIP3 provide a mechanistic link between ABA-mediated abiotic stress responses and oxylipin signaling.