Cytosporone B as a Biological Preservative: Purification, Fungicidal Activity and Mechanism of Action against Geotrichum citri-aurantii.

Chunxiao Yin,Hongxin Liu,Yang Shan,Weimin Zhang,Vijai Gupta,Liang Gong,Haibo Tan,Yueming Jiang

doi:10.3390/biom9040125

Abstract

To prevent citrus decay caused by Geotrichum citri-aurantii, 12 natural products were isolated from two endophytic fungi, in which cytosporone B was shown to have excellent bioactivity for control of G. citri-aurantii with median effect concentration (EC50) of 26.11 μg/mL and minimum inhibitory concentration (MIC) of 105 μg/mL, and also significantly reduced the decay of sugar orange during the in vivo trials. In addition, cytosporone B could alter the morphology of G. citri-aurantii by causing distortion of the mycelia and loss of membrane integrity. Differentially expressed genes (DEGs) between cytosporone B-treated and -untreated samples were revealed by Illumina sequencing, including 3540 unigenes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that most DEGs were related to metabolic production and cell membrane. These findings suggest cytosporone B is a promising biological preservative to control citrus decay and reveal the action mechanism of cytosporone B in relation to the destruction of the fungal cell membrane at both morphological and molecular levels.

Highlights

Citrus is one of the most important fruit crops with a global production of 146.4 million tons in2016 [1]
Previous studies have focused on the application of natural products for the control of G. citri-aurantii, demonstrating that essential oils and/or plant organic extracts can be effective in preventing postharvest citrus sour rot diseases [5,6] and that yeasts secreting hydrolytic enzymes have great potential for control of G. citri-aurantii [7]
The phytochemical study on the EtOAc extract of the fungi Phomopsis phyllanthicola A658 and Cytospora rhizophorae A761 resulted in the isolation of the twelve known compounds (Figure 1), including four octaketides—cytosporone B (1) [10], cytosporone M (2) [24], dothiorelone A

Summary

Introduction

Citrus is one of the most important fruit crops with a global production of 146.4 million tons in2016 [1]. Over 25% of produced citrus fruits are lost by postharvest decay, much of which is caused by fungal infections [2]. Biomolecules 2019, 9, 125 but long-term use of a single synthetic fungicide may induce pathogen resistance against many site-specific fungicides [4] It is well-recognized that the use of chemical and synthetic fungicides to control plant pathogens has many disadvantages and limitations, especially with respect to environmental and residual issues. Previous studies have focused on the application of natural products for the control of G. citri-aurantii, demonstrating that essential oils and/or plant organic extracts can be effective in preventing postharvest citrus sour rot diseases [5,6] and that yeasts secreting hydrolytic enzymes have great potential for control of G. citri-aurantii [7]. Microbial, plant and animal-derived compounds have been proposed as potential alternatives to synthetic fungicides for reducing the decay of postharvest citrus [8,9]

Methods

Results

Conclusion