Heat Shock Protein HSP24 Is Involved in the BABA-Induced Resistance to Fungal Pathogen in Postharvest Grapes Underlying an NPR1-Dependent Manner.

Although heat shock proteins (HSPs), a family of ubiquitous molecular chaperones, are well characterized in heat stress-related responses, their function in plant defense remains largely unclear. Here, we report the role of , a class B HSP from , in β-aminobutyric acid (BABA)-induced priming defense against the necrotrophic fungus in grapes. Grapes treated with 10 mmol L BABA exhibited transiently increased transcript levels of and several SA-inducible genes, including , , and . Additionally, phytoalexins accumulated upon inoculation with the gray mold fungus , which coincided with the action of a priming mode implicated in pathogen-driven resistance. Intriguingly, electrophoretic mobility shift (EMSA), yeast two-hybrid (Y2H) and His pull-down assays demonstrated that the nuclear chaperone cannot modulate the transcript of genes but does directly interact with or . Furthermore, we found that overexpression enhanced the transcript levels of NPR1 and SA-responsive genes (, , and ) and increased the resistance of transgenic to compared with wildtype Col-0. An opposite trend between CRISPR mutants of (the orthologous gene of in ) and wildtype plants was observed. Hence, our results suggest that has a potential role in NPR1-dependent plant resistance to fungal pathogen. BABA-induced priming defense in grapes may require posttranslational modification of the chaperone to activate transcript, leading to gene expressions and resistance phenotypes.