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

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.

Modulation of extracellular Penicillium expansum-driven acidification by Papiliotrema terrestris affects biosynthesis of patulin and has a possible role in biocontrol activity

“…During its infection process P. expansum produces also the mycotoxin PAT, although its active role in pathogenesis is controversial ( Prusky and Yakoby, 2003 ; Hadas et al, 2007 ; Prusky et al, 2007 ; Puel et al, 2010 ; Sanzani et al, 2012 ; Barad et al, 2013 ; Barad, Sionov et al, 2016 ; Li et al, 2020 ; Bartholomew et al, 2021 ). Although many aspects of PAT biosynthesis have been elucidated, to date little is known about the effect of pH modulation on PAT biosynthesis in vivo , i.e., on apple fruits infected by P. expansum ( Moake et al, 2005 ; Jimdjio et al, 2021 ). Similarly, no reports exist on the effect of biocontrol agents on host tissue pH when they counteract the attack on fruits by P. expansum .…”

“…Another relevant factor affecting PAT biosynthesis is the extracellular pH. For the majority of P. expansum strains, acidic conditions promote higher PAT production than alkaline environments ( Jimdjio et al, 2021 ). Nevertheless, the optimum of PAT biosynthesis is achieved in the pH range 4.0–5.0, while its production decreases at higher and lower pH values ( Zong et al, 2015 ).…”

AaCaMKs Positively Regulate Development, Infection Structure Differentiation and Pathogenicity in Alternaria alternata, Causal Agent of Pear Black Spot

“…The spore morphology was observed under scanning electron microscope (SEM) (JSM-5600LV) at 3000 magnification. The hyphae morphology was characterized as described by Jimdjio et al [ 46 ]. Briefly, 2 µL of WT and ΔAaCaMKs spore suspension were inoculated on PDA, covered with sterile cellophane, and then incubated at 28 °C for 3 d. The hyphae growing at the edge of the cellophane were cut and placed on a slide, then observed under a electron microscope and photographed.…”

Isolation of Main Pathogens Causing Postharvest Disease in Fresh Codonopsis pilosula during Different Storage Stages and Ozone Control against Disease and Mycotoxin Accumulation

“…A 5.0 g frozen sample was ground in liquid nitrogen, then was transferred to a 50 mL centrifuge tube with extraction solvent to extract mycotoxin. For different kinds of mycotoxin, various purification and detection methods were employed, patulin (PAT) purification and detection was carried out as described by the method [ 25 ]; trichothecene purification and detection was performed according to the method [ 26 ].…”