RNA Sequencing Reveals that Endoplasmic Reticulum Stress and Disruption of Membrane Integrity Underlie Dimethyl Trisulfide Toxicity against Fusarium oxysporum f. sp. cubense Tropical Race 4.

Cunwu Zuo,Weina Zhang,Zhongjian Chen,Yonghong Huang,Baihong Chen

doi:10.3389/fmicb.2017.01365

Abstract

Fusarium wilt of banana, a destructive disease that affects banana production, is caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4). In a previous study, we confirmed the strong inhibitory effects of Chinese leek (Allium tuberosum) on the incidence of this disease. Sulfur compounds are the primary antifungal constituents of Chinese leek. Among these, dimethyl trisulfide (DT) was the most abundant and exhibited the strongest inhibition of Foc TR4 growth and development. In the present study, the global gene expression profiles of Foc TR4 isolates treated with DT at 4,000-folds dilution (concentration of 1/4,000, v/v) for 1.5, 6, and 12 h were investigated by using RNA sequencing. The expression patterns of 15 DEGs were validated based on quantitative real-time PCR (qRT-PCR) assay. Untreated sample presented 2,556, 1,691, and 1,150 differentially expressed genes (DEGs) at 1.5, 6, and 12 h after the onset of the experiment, respectively, whereas DT-treated isolates presented 2,823, 3,546, and 6,197 DEGs. Based on Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, DEGs involved in endoplasmic reticulum (ER), glycosylation, and steroid biosynthesis were significantly inhibited by DT exposure. The similar expressional patterns of 15 DEGs between RNA-seq and qRT-PCR assays indicated the reliability of the RNA-seq data. In conclusion, ER stress related to glycosylation inhibition and damage to cell membrane integrity might contribute to the toxicity of DT against Foc TR4. As the results presented here evidenced changes in gene expression associated with DT exposure, which might be used to develop new approaches for controlling FWB.

Highlights

Fusarium oxysporum has been considered one of the most prevalent fungal pathogens, having a wide host range and causing severe losses in multiple crops such as tomato, cotton, maize, and banana (Dean et al, 2012; Aiyaz et al, 2016; Nirmaladevi et al, 2016)
Viability increased to 1.12, 1.49, 2.85, and 8.9-fold compared to the control at 6, 12, 24, and 36 h of culture, respectively, which were much lower than that of the untreated group at the same time point
With 1/2,000 dimethyl trisulfide (DT), the viability of Fusarium oxysporum f. sp. Cubense (Foc) TR4 conidia were decreased to 4% that of the untreated conidia at 6 h, and no conidia survived after 12 h incubation at this concentration

Summary

Introduction

Fusarium oxysporum has been considered one of the most prevalent fungal pathogens, having a wide host range and causing severe losses in multiple crops such as tomato, cotton, maize, and banana (Dean et al, 2012; Aiyaz et al, 2016; Nirmaladevi et al, 2016). Many antifungal secondary metabolites have been identified from plants and microorganism (Paiva et al, 2010; Coleman et al, 2011), and the identification of novel antifungal targets for use as control agents is currently becoming an important strategy (De Backer and Van Dijck, 2003; Walsh et al, 2010). Some of these targets include chitin, the major component of the fungal cell wall, and ergosterol, which is essential to membrane formation. It is urgent to identify alternative therapeutics for future use

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