Abstract: Objective: This work aims to study the physiological function of V-ATPase membrane subunit H (VMAH) protein in the growth of the citrus green mold fungus Penicillium digitatum and to evaluate its feasibility as a target of anti-citrus green mold drugs through gene interference and overexpression. Methods: The effect of silencing and overexpression of the VMAH gene was investigated on the growth characteristics of P. digitatum cells under normal and stress conditions, as measured by mycelial growth and spore germination. Results: Under normal growth conditions, VMAH silencing significantly inhibited the growth of P. digitatum mycelia, while VMAH overexpression showed a significant promoting effect. Under different pH environments, VMAH silencing significantly inhibited the growth of P. digitatum hyphae, especially under acidic (pH lower than 2) and alkaline (pH higher than 8) conditions, while overexpression of the VMAH gene promoted mycelial growth to a certain extent, especially at pH 6. Compared with the wild-type strain, silencing of the VMAH gene increased the sensitivity to the stress of extracellular Ca2+, Cu2+, Fe2+ and other metal ions and to proton pump inhibitor fungicides, especially the V-ATPase specific inhibitor bafilomycin A1, while VMAH overexpression significantly reduced the sensitivity to proton pump inhibitor fungicides. Conclusion: VMAH plays an important role in the growth of P. digitatum and is a potential target for the development of low-resistant postharvest citrus fungicides.

Key words: Penicillium digitatum; V-ATPase subunit H; gene silencing; overexpression; growth characteristics