Enhancement of disease resistance against Alternaria alternata in winter jujube fruit by phenyllactic acid through regulating Ca2+ signaling transduction and mitogen-activated protein kinase cascades

Abstract

Alternaria rot caused by Alternaria alternata is one of destructive fungal diseases of postharvest winter jujubes. This study performed to evaluate the potential mechanisms participated in the enhancement disease resistance of winter jujubes by phenyllactic acid (PLA). Results demonstrated that PLA reduced the lesion diameter of A. alternata-inoculated winter jujubes. Additionally, PLA treatment led to an up-regulation in the transcription levels of ZjCML23/28, ZjCIPK11/12/20, ZjCDPK1/3/5, ZjMAPKKK18, ZjMAPKK6, and ZjMAPK7/19 as well as ZjNPR1 and ZjWRKY14/22/44/55/64 in fruit. Conversely, the transcription levels of ZjMAPK15 and ZjMAPKKK17 were down-regulated. Simultaneously, PLA enhanced the gene transcription levels and enzymatic activities of peroxidase, β-1,3-glucanase, and chitinase in winter jujubes, while facilitating the deposition of lignin, flavonoids, and total phenolics. Overall, these findings suggest that PLA enhances the resistance of winter jujube fruit via positively modulating the transcription of key Ca2+ receptor protein, activating the mitogen-activated protein kinase cascades, and potentially involving NPR1 and WRKY transcription factors.