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Postharvest disease caused by fungi is a major issue that leads to quality decline and economic losses in mango fruit during storage and distribution. TGA transcription factors and pathogenesis-related proteins (PR) play crucial roles in modulating plant tolerance to pathogens. However, the roles of TGAs in the disease resistance of mango fruit remain unclear. Here, we investigated the impact of applying the antagonist Bacillus siamensis (N-1) on disease occurrence and the expression levels of MiTGA1 and MiPR1 genes in “Tainong No. 1” mango. We also explored the molecular mechanism of MiTGA1 interaction with MiPR1 gene. Results demonstrated that N-1 treatment significantly increased the level of hydrogen peroxide (H2O2) and effectively suppressed disease expansion during mango storage at 25 °C. Analyses of transcriptome data and qRT-PCR revealed the obvious up-regulation of MiTGA1 and MiPR1 genes in response to the N-1 treatment. Further subcellular localization identified the MiTGA1 protein as being located in the nucleus. Yeast one-hybrid (Y1H) and dual-luciferase reporter (DLR) assays confirmed that MiTGA1 could bind to the MiPR1 promoter and activate its transcription. Furthermore, transient over-expression of MiTGA1 in mango was found to enhance the accumulation of disease-resistant substances such as H2O2 by modulating MiPR1 expression, thereby bolstering the disease resistance of mango fruit. Our study suggests that MiTGA1 is a promising target gene and its interaction with MiPR1 may contribute to disease resistance induction and decay mitigation in postharvest mango fruit.

Pericarp browning, postharvest disease, and a short storage life are the leading causes of economic losses in the litchi industry globally. Energy metabolism plays an integral role in regulating browning, disease resistance, and the shelf-life of litchi fruit. The ability of Bacillus siamensis (N-1) to control postharvest diseases and maintain the quality of a variety of tropical fruits has previously been reported, however its effect on litchi fruit has not been explored. In the present study, we investigated the effect of Bacillus siamensis (N-1) on the postharvest energy metabolism of litchi fruit and its relation to pericarp browning, as well as the expression of energy-related genes. Results indicated that litchi fruit treated with Bacillus siamensis (N-1) exhibited a significant improvement in storability as evidenced by a decrease in the rate of the browning index (BI), color change, rate of weight loss, and laccase (LAC) and polyphenol oxidase (PPO) activity. There was also an increase in the energy status of litchi fruit due to the enhanced activity of Ca2+-ATPase, H+-ATPase, oxidase (CCO), cytochrome C, and succinic dehydrogenase (SDH), as well as the expression of their corresponding genes. LcVHA2 and LcVHA3, two major vacuolar-type H+-ATPase genes, were cloned and characterized. Phylogenetic analysis revealed that these genes are members of the V-ATPase subunit D and E gene family, respectively. Both heterologous (in tomato) and homologous (in litchi) transient overexpression (OE) assays indicated that both LcVHA2 and LcVHA3 have the potential to delay changes in fruit coloration and pericarp browning, but also increase ADP, ATP, and V-H+-ATPase activity, as well as the energy charge (EC) of fruit. Collectively, results indicated that the LcVHA2 and LcVHA3 play a critical role in preventing the browning and senescence of litchi fruit. This study provides new information on the ability of Bacillus siamensis (N-1), which has been previously demonstrated to be an effective postharvest biocontrol agent, to also improve the storage life of litchi fruit.