CHI-Phe-Arg coating delays postharvest grape berry softening via the VviNAC25-VviNAC83-VviCESA5 module

Abstract

Table grapes (Vitis vinifera L.) are highly susceptible to postharvest softening and decay. This study investigated the preservative effects and molecular mechanisms of a composite coating consisting of chitosan (CHI) combined with phenylalanine (Phe) and arginine (Arg), designated as CHI-Phe-Arg, on ‘Kyoho’ table grapes. This composite coating significantly suppressed postharvest decay, berry abscission, and weight loss, inhibited the activities of cell wall-degrading enzymes (PG and Cx), and delayed fruit softening. To elucidate its molecular mechanism, transcriptome sequencing was performed on grape berries at 3 d, 6 d, and 9 d post-treatment. Transcriptome analysis identified two significantly upregulated NAC transcription factors, VviNAC25 and VviNAC83, as well as the cellulose synthase gene VviCESA5. Promoter analysis revealed the presence of NAC-binding sites (CATGTG/CGTA/TACG/CGTG) in the VviCESA5 promoter. Dual-luciferase and yeast one-hybrid assays confirmed that VviNAC25 and VviNAC83 directly bind to and activate the transcription of VviCESA5, exhibiting a synergistic effect. Luciferase complementation imaging (LCI) and bimolecular fluorescence complementation (BiFC) assays further confirmed the interaction between VviNAC25 and VviNAC83, supporting their formation of a transcription factor complex. Transient overexpression assays further demonstrated that co-expression of VviNAC25 and VviNAC83 significantly enhanced the expression of VviCESA5. In conclusion, the CHI-Phe-Arg composite coating delays grape softening by activating the VviNAC25/VviNAC83-VviCESA5 transcriptional module, providing a theoretical basis for developing chitosan-amino acid composite coating technologies for grape preservation.