CiPLDδ2 determines postharvest storage stability of pecan by regulating membrane lipid degradation and the antioxidant system

Abstract

The high oil content, combined with unsaturation, of pecan ( Carya illinoinensis ) kernels renders them prone to oxidation as well as hydrolysis during storage, thereby causing quality deterioration. Previous evidence indicates that Phospholipase D δ2 in C. illinoinensis ( CiPLDδ2 ) responds to reactive oxygen species while participating in lipid deterioration. In this study, analysis of storage stability across pecan varieties, together with CiPLD family members, showed that varieties with low CiPLDδ2 abundance yet high storage tolerance exhibited strong antioxidant capacity coupled with oil body stability, which contributed to maintaining low acid and peroxide values. Transient overexpression and silencing of CiPLDδ2 , along with heterologous overexpression in Arabidopsis, demonstrated that CiPLDδ2 positively regulates PLD activity, promotes phospholipid as well as triglyceride hydrolysis, elevates free fatty acids and lysophospholipids, thereby inducing accumulation of the lipid peroxidation product malondialdehyde. Together with metabolomics, the data further revealed that CiPLDδ2 modulates energy, phospholipid, as well as phenolic metabolism, disrupts the ascorbate-glutathione cycle, reduces ascorbate peroxidase activity while altering ascorbate and glutathione contents. In conclusion, CiPLDδ2 acts as a positive regulator of postharvest lipid deterioration in pecan kernels by hydrolyzing membrane lipids, disrupting oil body structure, inducing oxidative stress, and compromising the antioxidant system.