Regulation of redox status contributes to priming defense against Botrytis cinerea in grape berries treated with β-aminobutyric acid

This study aimed to determine the specific form of the disease resistance using BABA elicitation and to illustrate the involvement of an alteration of the redox status in the BABA-activated defense response in grape berries. The BABA treatment at 10 mmol L-1 primed the grape berries for efficient disease resistance against Botrytis cinerea infection, as exhibited by the significantly enhanced levels of PR genes upon the B. cinerea challenge. In addition, the priming defense was associated with the onset of the SA-dependent SAR reaction. The BABA treatment induced higher activities of key enzymes in PPP and ascorbate-glutathione cycle, thus promoting the pools of GSH and NADPH and correspondingly elevating the [NADPH]/[NADP(+)] and [GSH]/[GSSG] ratios, which shifted the cellular redox towards a highly reductive condition. Meanwhile, the BABA-treated fruits also showed higher contents of intercellular redox signalling molecules, such as NO and SA, than those in the controls. This increase in the redox status coincided with the enhanced expression of a series of PR genes and with lower disease incidence. In contrast, 6-AN completely diminished the increases in the NADPH and GSH pools elicited by BABA in grape berries in parallel with an inhibitory effect on induction of the PR genes transcript levels. Thus, these findings indicated that BABA can prohibit the oxidation of the redox state necessary for the induction of a priming response in grape berries against B. cinerea infection.