Glycine betaine and MiWRKY53 enhance antioxidant capacity and disease resistance against Colletotrichum gloeosporioides in mango fruit

Abstract

Mangoes, a quintessential tropical fruit, are highly susceptible to senescence and spoilage caused by Colletotrichum gloeosporioides during postharvest storage. Glycine betaine (GB), a natural compound with broad applications in the food industry, was investigated for its effects on the postharvest physiology, quality characteristics, and antioxidant activity of “Tainong No.1” mangoes. This study further elucidated the regulatory role of MiWRKY53 in the GB-mediated response. Results revealed that 10 mM GB treatment significantly suppressed the increase in the disease index while preserving titratable acidity (TA) and ascorbic acid (Vc) contents compared to the control (P < 0.05). GB treatment also reduced respiration rate, cell membrane permeability, and malondialdehyde (MDA) content, maintaining fruit firmness and delaying softening during storage. Moreover, GB treatment enhanced the activities of antioxidant enzymes, including phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), chalcone isomerase (CHI), and catalase (CAT), which promoted the accumulation of antioxidant compounds such as total phenols, flavonoids, and lignin. An in vivo assay further demonstrated that GB disrupted fungal mycelium structure and inhibited spore germination in wounded mango fruit. Furthermore, GB treatment significantly upregulated the transcription levels of key genes, including MiPAL, Mi4CL, MiCHI, and MiWRKY53. MiWRKY53 was identified as a WRKY transcription factor that shows close evolutionary similarity to Pistacia vera based on Neighbor-joining phylogenetic tree analysis. Functional assays revealed that transient overexpression of MiWRKY53 enhanced CHI activity, reduced disease lesions, and maintained green pigmentation in mango discs and tobacco leaves. Conversely, virus-induced gene silence (VIGS) of MiWRKY53 resulted in adverse effects. This study highlights the potential of 10 mM GB treatment to control postharvest diseases and extend the shelf life of mangoes. The findings provide practical insights into leveraging natural compounds and genetic regulation for improving postharvest mango fruit quality.