Abstract
Microbial secondary metabolites produced by Streptomyces are applied to control plant diseases. The metabolite, ε-poly-l-lysine (ε-PL), is a non-toxic food preservative, but the potential application of this compound as a microbial fungicide in agriculture is rarely reported. In this study, the effect and mode of action of ε-PL on two necrotrophic pathogenic fungi, Sclerotinia sclerotiorum and Botrytis cinerea, were investigated. The results showed that ε-PL effectively inhibited the mycelial growth of S. sclerotiorum and B. cinerea with EC50 values of 283 μg/mL and 281 μg/mL, respectively. In addition, ε-PL at the dose of 150 and 300 μg/mL reduced S. sclerotiorum sclerotia formation. The results of the RNA-seq and RT-qPCR validation indicated that ε-PL significantly regulated the gene expression of critical differential expressed genes (DEGs) involved in fungal growth, metabolism, pathogenicity, and induced an increase in the expression of the fungal stress responses and the detoxification genes. These results provided new insights for understanding the modes of action of ε-PL on S. sclerotiorum and B. cinerea and improved the sustainable management of these plant diseases.
Highlights
Differential expression analysis of ε-PL-Ss (S. sclerotinia treated with ε-PL) versus mockSs (S. sclerotinia treated with distilled water), and ε-PL-Bc (B. cinerea treated with εPL) vs. mock-Bc (B. cinerea treated with distilled water) were performed using the DEseq
The results showed that the increased concentrations of ε-PL at 400, 600 and 1200 μg/mL progressively inhibited the necrotic lesion formed by S. sclerotiorum (Figure 3)
We investigated the functions of ε-PL on the induction of host defense responses against the infection of the tobacco mosaic virus (TMV) [25], as well as the anti-fungal mechanisms of ε-PL on A. alternata [21]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. This fungal pathogen poses a threat to dicotyledonous crops such as sunflower, soybean, peanut, oilseed rape, lentils and various vegetables, and monocotyledonous species such as onion, tulip, and garlic [4] This fungus can produce sclerotia, which serve as long-term survival structures under adverse environments and play critical roles in disease progression [5,6]. The microbial source agent ε-PL significantly suppressed mycelial growth and regulated the expression of the critical genes involved in fungal growth, pathogenicity, and the stress responses and detoxification of necrotrophic fungi, S. sclerotiorum and B. cinerea. Such results provided new insights for the mode of action of ε-PL in the management of plant diseases caused by S. sclerotiorum and B. cinerea
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