Effect of Ambient pH on Growth, Pathogenicity, and Patulin Production of Penicillium expansum.

Carelle Kouasseu Jimdjio,Huali Xue,Rui Zhang,Lan Li,Lumei Pu,Qili Liu,Yang Bi,Mina Nan

doi:10.3390/toxins13080550

Abstract

Penicillium expansum is an important postharvest pathogen of pomaceous fruit and a causal agent of blue mold or soft rot. In this study, we investigated the effect of ambient pH on growth, ultrastructure alteration, and pathogenicity of P. expansum, as well as accumulation of patulin and expression of genes involved in patulin biosynthesis. Under different pH, the fungus was routinely cultured and collected for growth, pathogenicity, patulin production, and gene expression studies using transmission electron microscopy, apple inoculation, HPLC, and RT-qPCR methods. Different ambient pH had significant impact on expression of genes and growth factors involved in patulin biosynthesis. Under same range of pH, gene expression profile, growth factors, and patulin accumulation (in vivo and in vitro) all showed similar changing trends. A well-developed cell was observed in addition to upregulation of genes at pH between pH 5.0 and 7.0, while the opposite was observed when pH was too basic (8.5) or too acid (2.5). Additionally, ambient pH had direct or indirect influence on expression of PecreaA, PelaeA, and PepacC. These findings will help in understanding the effect of ambient pH on growth, pathogenicity, and patulin production and support the development of successful methods for combating P. expansum infection on apple fruits.

Highlights

Penicillium expansum is a ubiquitous, opportunistic, and saprophytic fungus belonging to the Ascomycete sub-group and Trichomaceae family
The effect of pH on growth factors was established by culturing P. expansum in potato dextrose broth (PDB) modified at various pH and incubated at different periods
The results showed enormous expresFactors and Proteins Involved in Patulin Biosynthesis sion of genes at pH 5.0 followed by pH 7.0

Summary

Introduction

Penicillium expansum is a ubiquitous, opportunistic, and saprophytic fungus belonging to the Ascomycete sub-group and Trichomaceae family. It is one of the most important postharvest pathogens of pomaceous fruits (e.g., apples and pears) and a causal agent of blue mold or soft rot [1]. The fungus attacks fruits through injuries or mechanical wounds during postharvest handling and storage, leading to blue mold on fruits. The blue mold causes substantial economic loss around the world and leads to patulin contamination with public health consequences [2]. Patulin belongs to a shortlist of mycotoxins (including aflatoxins, ochratoxin A, zearalenone, fumonisins, and trichothecenes) found in foods and their contamination levels are controlled in many countries around the world.

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