Abstract
Anthracnose caused by Colletotrichum gloeosporioides is a major disease leading to postharvest loss of mango fruit. Melatonin (MT) is a natural bioactive molecule that has multiple physiological functions in plants. This study investigated the effect of exogenous MT on mango disease resistance against C. gloeosporioides and related molecular mechanism. MT treatment at 1 mmol L-1 limited the expansion of anthracnose in mango inoculated with C. gloeosporioides, which was associated with increased level of defense-related indexes, including activities of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL) and peroxidase (POD), expression of MiPAL, Mi4CL and MiPOD and contents of total phenolics, flavonoids and lignin. RT-qPCR analysis of 15 MiWRKY members revealed that MiWRKY45 had the highest expression in response to MT + C. gloeosporioides. MiWRKY45 transcription factor was identified as a nucleus-localized transcriptional activator based on subcellular localization and transcriptional activation assays. MiWRKY45 bound to W-box motif and activated the expression of MiPAL, Mi4CL and MiPOD, as verified by DNA affinity purification-seq (DAP-seq), yeast one-hybrid (Y1H) and dual-luciferase reporter (DLR) assays. Transient transformation analysis revealed that MiWRKY45 positively regulated phenylpropanoid pathway, thereby enhancing mango resistance. These results suggest that MiWRKY45, as a positive regulator, is involved in MT-induced resistance against anthracnose in mangoes.
Published Version
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