New Insight Into Pathogenicity and Secondary Metabolism of the Plant Pathogen Penicillium expansum Through Deletion of the Epigenetic Reader SntB

Abstract

<i>Penicillium expansum</i> is one of the most harmful post-harvest pathogens of pomaceous fruits and the causal agent of blue rot disease. During infection, <i>P. expansum</i> produces the toxic secondary metabolites patulin and citrinin that can impact virulence and, further, render the fruit inedible. Several studies have shown that epigenetic machinery controls synthesis of secondary metabolites in fungi. In this regard, the epigenetic reader, SntB, has been reported to govern the production of multiple toxins in <i>Aspergillus</i> species, and impact virulence of plant pathogenic fungi. Here we show that deletion of <i>sntB</i> in <i>P. expansum</i> results in several phenotypic changes in the fungus including stunted vegetative growth, reduced conidiation, but enhanced germination rates as well as decreased virulence on Golden Delicious apples. In addition, a decrease in both patulin and citrinin biosynthesis <i>in vitro</i> and patulin in apples, was observed. SntB positively regulates expression of three global regulators of virulence and secondary metabolism (LaeA, CreA, and PacC) which may explain in part some of the phenotypic and virulence defects of the PeΔ<i>sntB</i> strain. Lastly, results from this study revealed that the controlled environmental factors (low temperatures and high CO₂ levels) to which <i>P. expansum</i> is commonly exposed during fruit storage, resulted in a significant reduction of <i>sntB</i> expression and consequent patulin and citrinin reduction. These data identify the epigenetic reader SntB as critical factor regulated in post-harvest pathogens under storage conditions and a potential target to control fungal colonization and decaying of stored fruit.