Sodium nitroprusside (SNP) generated nitric oxide delays senescence of cowpea (Vigna unguiculata (L.) Walp)

Cowpea (Vigna unguiculata (L.) Walp) is prone to water loss and shriveling after harvest. Sodium nitroprusside (SNP) as a generator of nitric oxide acts as a senescence retarding agent. In this study, the influence of SNP on cowpea senescence during storage at 15 °C for 8 d has been investigated. SNP treatment (0.3 mM) decreased the mass loss and maintained the hardness, total chlorophyll, and vitamin C content of the cowpeas. SNP suppressed the expression of the genes involved in ethylene signaling (SAM1, ETR2, ERFs), cell wall disassembly (PE2, PL5, PG), and the lignin synthesis genes (4CL, CCR, and CAD), while inducing the expression of defense and resistance-related genes (KCS, ABCG, BAK1, PR-4, and CpPR3). The major differentially accumulated metabolites in SNP-treated cowpeas were flavonoids, phenolic acids, and alkaloids. SNP-induced differentially expressed proteins that are involved in lignification (4CL, CAD, and POD), texture-related processes (PL5, PE, and EG), and disease resistance (PBSI, PR1, and SCP). Overall, the study revealed that SNP-generated NO suppressed ethylene signaling, inhibited lignin accumulation, regulated wax, suberin, and cuticle biosynthesis, and enhanced defense processes, resulting in higher-quality cowpeas than those of the untreated controls.