The Jasmonic Acid Biosynthetic Genes SmLOX4 and SmLOX5 Are Involved in Heat Tolerance in Eggplant.

High-temperature stress (HTS) affects the growth and production of vegetable crops, including eggplant (Solanum melongena L.). Jasmonic acid (JA) plays key roles in regulating resistance to biotic and abiotic stresses in plants. Nonetheless, reports on the role of JA in heat tolerance in eggplant are rare. Herein, the effects of JA on heat tolerance in eggplant and the functions of the JA biosynthetic genes SmLOX4 and SmLOX5 were analyzed. The results showed that the JA content increased under high-temperature treatment (HTT) and exogenous methyl jasmonate (MeJA) treatment reduced the damage caused by HTT to eggplant. The expression of SmLOX4 and SmLOX5 was induced by HTT and significantly positively correlated with JA biosynthesis. SmLOX4 and SmLOX5 were localized in chloroplasts. The silencing of SmLOX4 and SmLOX5 by virus-induced gene silencing suppressed the heat tolerance of eggplant, whereas the overexpression of SmLOX4 and SmLOX5 enhanced the heat tolerance of Arabidopsis thaliana. JA content and the expression of JA signaling-related genes decreased in the SmLOX4- and SmLOX5-silenced plants but increased in the OE-SmLOX4 and OE-SmLOX5 transgenic plants. These results revealed that SmLOX4 and SmLOX5 improved eggplant heat tolerance by mediating JA biosynthesis and JA signaling pathways.