Patatin-like phospholipase A-induced alterations in lipid metabolism and jasmonic acid production affect the heat tolerance of Gracilariopsis lemaneiformis

Abstract

High temperatures seriously limit the growth and productivity of Gracilariopsis lemaneiformis. By hydrolyzing glycerolipids into lysophospholipids (LPs) and free fatty acids (FFAs), patatin-like phospholipase A (pPLA) plays an important role in stress responses. GlpPLA expression was up-regulated under heat stress, however, the regulation of pPLA in heat tolerance of G. lemaneiformis is unknown. In this study, G. lemaneiformis under heat stress was treated with bromoenololide (BEL), a chemical inhibitor of pPLA, to evaluate the cellular function of pPLA in this species. When pPLA was inhibited through BEL treatment, the sensitivity of G. lemaneiformis to heat stress increased and the biomass and maximum and effective quantum yield of photosystem II decreased. Moreover, BEL treatment resulted in a significant decrease in many lipid molecular species, all of which are mainly composed of 16C, 18C, and 20C fatty acids. Consistently, FFA levels and LPs contents in G. lemaneiformis under BEL treatment showed a significant decrease. The first step in the synthesis of jasmonic acid (JA) is the lipoxygenase (LOX)-mediated oxygenation of linolenic acid (C18:3). BEL treatment decreased JA and C18:3 accumulation and markedly downregulated the expression of GILOX under heat stress. Together, these results indicate that pPLA is closely related to the growth of G. lemaneiformis under heat stress, and pPLA is involved in the lipid metabolism and JA biosynthesis of G. lemaneiformis in response to heat stress. This research broadens the understanding of the heat stress adaptation mechanism of G. lemaneiformis.