The lipoxygenase CmLOX13 from oriental melon enhanced severe drought tolerance via regulating ABA accumulation and stomatal closure in Arabidopsis

Abstract

Lipoxygenase (LOXs) play essential roles in responding to abiotic stresses in plants, however, the mechanisms of CmLOXs from oriental melon remain largely unknown. In this study, we aimed to explore the function and mechanism of CmLOX13 in drought stress. qRT-PCR analysis showed that CmLOX13 was upregulated dramatically by drought stress. Phenotypic and physiological analysis showed that heterologous overexpression of CmLOX13 (CmLOX13-OX) improved drought tolerance in Arabidopsis. Endogenous abscisic acid (ABA) contents significantly increased in the CmLOX13-OX lines after drought treatment. RNA-seq and qRT-PCR results showed that the transcription of NCED3 and NCED5, key genes in ABA biosynthesis process changed little, while the expression of four key genes CYP707A1 to CYP707A4 in ABA catabolism pathway were all significantly down-regulated in transgenic plants. However, jasmonic acid (JA) contents in CmLOX13-OX lines were lower than that in WT under control and drought conditions accompanied by the higher expression of the JA catabolism genes. Exogenous ABA and its inhibitor can alter drought stress resistance both in WT and CmLOX13-OX. In addition, physiological and transcriptome analysis indicated that stomatal closure was mediated by ABA signal transduction pathway. Our results demonstrated that CmLOX13 functioned as a positive regulator by modulating ABA level through decreasing catabolism related genes expression and ABA-induced stomatal closure in response to drought stress.