AUTHOR=Li Chunhong , Cao Shifeng , Wang Kaituo , Lei Changyi , Ji Nana , Xu Feng , Jiang Yongbo , Qiu Linglan , Zheng Yonghua 

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

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.646147

DOI=10.3389/fpls.2021.646147

ISSN=1664-462X

ABSTRACT=<p>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 <italic>VvHSP24</italic>, a class B HSP from <italic>Vitis vinifera</italic>, in β-aminobutyric acid (BABA)-induced priming defense against the necrotrophic fungus <italic>Botrytis cinerea</italic> in grapes. Grapes treated with 10 mmol L<sup>–1</sup> BABA exhibited transiently increased transcript levels of <italic>VvNPR1</italic> and several SA-inducible genes, including <italic>PR1</italic>, <italic>PR2</italic>, and <italic>PR5</italic>. Additionally, phytoalexins accumulated upon inoculation with the gray mold fungus <italic>B. cinerea</italic>, 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 <italic>VvHSP24</italic> cannot modulate the transcript of <italic>PR</italic> genes but does directly interact with <italic>VvNPR1 in vivo</italic> or <italic>in vitro</italic>. Furthermore, we found that <italic>VvHSP24</italic> overexpression enhanced the transcript levels of NPR1 and SA-responsive genes (<italic>PR1</italic>, <italic>PR2</italic>, and <italic>PR5</italic>) and increased the resistance of transgenic <italic>Arabidopsis thaliana</italic> to <italic>B. cinerea</italic> compared with wildtype Col-0. An opposite trend between CRISPR mutants of <italic>AtHSFB1</italic> (the orthologous gene of <italic>VvHSP24</italic> in <italic>Arabidopsis</italic>) and wildtype plants was observed. Hence, our results suggest that <italic>VvHSP24</italic> 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 <italic>VvHSP24</italic> to activate <italic>VvNPR1</italic> transcript, leading to <italic>PR</italic> gene expressions and resistance phenotypes.</p>