Non-specific phospholipase C5 and diacylglycerol promote lateral root development under mild salt stress in Arabidopsis

Developing a robust root system is crucial to plant survival and competition for soil resources. Here we report that the non-specific phospholipase C5 (NPC5) and its derived lipid mediator diacylglycerol (DAG) mediate lateral root (LR) development during salt stress in Arabidopsis thaliana. T-DNA knockout mutant npc5-1 produced few to no LR under mild NaCl stress, whereas overexpression of NPC5 increased LR number. Roots of npc5-1 contained a lower level of DAG than wild type, whereas NPC5 overexpressor exhibited an increase in DAG level. Application of DAG, but not phosphatidic acid, fully restored LR growth of npc5-1 to that of wild type under NaCl stress. NPC5 expression was significantly induced in Arabidopsis seedlings treated with NaCl. Npc5-1 was less responsive to auxin-mediated root growth than the wild type. These results indicate that NPC5 mediates LR development in response to salt stress and suggest that DAG functions as a lipid mediator in the stress signalling.