The role of Penicillium expansum histone deacetylases HosA and HosB in growth, development, and patulin production

Histone modifications are key epigenetic mechanisms for gene regulation in response to environmental stimuli. Histone acetylation is crucial for regulating chromatin accessibility and is controlled by histone-modifying enzymes: histone acetyltransferases (HATs) and histone deacetylases (HDACs). This study examined the roles of two HDACs, HosA and HosB, in the fungus Penicillium expansum. While the deletion of hosB did not affect the phenotype, HosA was found to play a crucial role in growth, development, and conidiation. The ΔhosA strain exhibited a characteristic fluffy phenotype and a significant reduction in conidiation. Expression analysis indicated that these differences were related to lower expression of the core regulatory gene wetA, and, to a lesser extent, brlA and abaA. Additionally, the growth of ΔhosA was negatively affected by the addition of calcofluor white and sodium chloride, while the deletion of hosA increased tolerance to sodium dodecyl sulfate and hydrogen peroxide on solid media. Furthermore, the ΔhosA strain showed an abnormal pattern of patulin production during in vitro growth, and reduced virulence likely due to growth retardation and impaired conidiation. These findings suggest that HosA is an epigenetic regulator of conidiation and plays an indirect role in secondary metabolite production and virulence in P. expansum.