Effect of Cinnamaldehyde and Citral Combination on Transcriptional Profile, Growth, Oxidative Damage and Patulin Biosynthesis of Penicillium expansum.

Yuan Wang,Kewei Feng,Tianli Yue,Zhiwei Zhang,Yahong Yuan,Haihua Yang

doi:10.3389/fmicb.2018.00597

Abstract

Penicillium expansum, as a main postharvest pathogen of fruits, can secrete patulin (PAT), causing fruit decay and health problems. In this study, the antifungal test, SEM (scanning electron microscope) observation, transcriptional profile, PAT biosynthesis, and physiological characters of P. expansum exposed to cinnamaldehyde and citral combination (Cin/Cit) were evaluated. Cin/Cit could inhibit the mycelial growth and spore germination of P. expansum in a dose-dependent manner. Besides, Cin/Cit caused spores and mycelia wrinkled and depressed by SEM observation. Gene expression profiles of P. expansum were conducted by RNA sequencing (RNA-seq) in the presence or absence of Cin/Cit treatment. A total of 1713 differentially expressed genes (DEGs) were obtained, including 793 down-regulated and 920 up-regulated genes. Most of the DEGs participated in the biosynthesis of secondary metabolites, amino acid metabolism, and oxidation-reduction process, etc. Cin/Cit induced the dysfunction of the mitochondrial membrane, causing the potential influence on energy metabolism and reactive oxidative species production. The changes of superoxide dismutase (SOD) and catalase (CAT) activities combing with the increase of hydrogen peroxide content indicated the oxidative stress on P. expansum induced by Cin/Cit, which corresponded well with the transcriptional results. Moreover, both the RNA-seq data and the qRT-PCR showed the remarkable down-regulation of genes included in the PAT biosynthetic pathway under the Cin/Cit treatment. These findings provided more useful information about the antifungal mechanism of Cin/Cit against P. expansum at molecular and gene levels and suggested that Cin/Cit is a potential candidate to control P. expansum.

Highlights

Fungal and mycotoxins contaminations are the major problems in agricultural products safety and human health
The extension of the colony radius and the accumulation of the biomass weight of P. expansum were completely inhibited by Cin/Cit at minimum inhibitory concentration (MIC) and 2 MIC during the whole incubation period (Figures 1A,B)
With regard to the spore germination rate of P. expansum at 12 h, spores treated with 1/4 MIC (84.1%) showed no significant difference compared with controls (87.6%)

Summary

Introduction

Fungal and mycotoxins contaminations are the major problems in agricultural products safety and human health. The dual combination of the trans-cinnamaldehyde-citral emulsion at 100 μg/ml was proved to inhibit Zygosaccharomyces bailii in apple juice stored at 20◦C for 27 days (Loeffler et al, 2014). Both cinnamaldehyde and citral exhibit direct inhibition to the pathogen, as well as indirectly control the pathogen growth by improving the host’s defense system (Fan et al, 2014; Jiang et al, 2015)

Methods

Results

Conclusion