NtCML19 Is Recruited by Tobacco to Interact With the Deacetylase Protein RsDN3377 of Rhizoctonia solani AG3 ‐ TB , Inhibiting Fungal Infection

The necrotrophic fungal pathogen Rhizoctonia solani anastomosis group 3 (AG3‐TB) is a major cause of global tobacco crop yield losses. Secreted proteins produced by filamentous fungi, as important virulence factors, play a core role in the interaction between plants and pathogens. In this study, we identified a secretory protein, RsDN3377, which localised to the intercellular space and induced cell death in Nicotiana benthamiana . Heterologous expression in Escherichia coli coupled with matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry analysis confirmed RsDN3377 possessed deacetylase activity. In addition, RsDN3377 was an essential pathogenicity factor for mycelial development by double‐stranded RNA‐mediated gene silencing. Through yeast two‐hybrid and bimolecular fluorescence complementation assays, we demonstrated that RsDN3377 interacted with the calcium‐binding protein NtCML19. In addition, transgenic Yunyan 87 overexpressing NtCML19 exhibited enhanced resistance to R. solani AG3‐TB infection. Microscale thermophoresis analysis verified the calcium‐binding activity of NtCML19. These lines of evidence indicate that the deacetylase RsDN3377 is secreted by R. solani AG3‐TB, and this protein, critical for promoting fungal mycelial development and pathogenicity, was disrupted by its resistance‐related interaction with NtCML19.