Figure 8.

A novel pathway for the degradation of phospholipids and Pi recycling via a GPX-PDE-mediated pathway during phosphate limitation. Under Pi limitation, plant phospholipids (PC and PI) decrease. The degradation of PC mediated by either nonspecific phospholipase C (NPC4 and NPC5) or phospholipase D (PLDζ1 and PLDζ2) with the subsequent release of Pi is well documented (pathway in box). We propose an alternative phospholipid degradation and Pi recycling pathway that catabolizes PC and PI. PC and PI are deacylated into GPC and GPI by Pi deficiency-induced phospholipase A₂ (PLA2) and lysophospholipase. GPC and GPI are further hydrolyzed by Pi deficiency-induced GPX-PDE1 and GPX-PDE2 to glycerol-3-phosphate (G3P) and choline (Chol) or inositol (Ins). G3P is subsequently catalyzed by Pi deficiency-induced acid phosphatase (AP) to release Pi and glycerol. DGDG, Digalactosyldiacylglycerol; DGD, DGDG synthase; FA, fatty acid; LysoPtdC, lysophosphatidylcholine; LysoPtdIns, lysophosphatidylinositol; MGDG, monogalactosyldiacylglycerol; MGD, MGDG synthase; PA, phosphatidic acid; PChol, phosphocholine.