Suppression of Sclerotinia sclerotiorum by the Induction of Systemic Resistance and Regulation of Antioxidant Pathways in Tomato Using Fengycin Produced by Bacillus amyloliquefaciens FZB42.

Ayaz Farzand,Xuewen Gao,Abdur Rashid Khan,Taha Majid Mahmood Sheikh,Muhammad Ayaz,Anam Moosa,Hafiz Abdul Samad Tahir,Venance Colman Massawe,Muhammad Zubair

doi:10.3390/biom9100613

Abstract

Lipopeptides from Bacillus species exhibit promising biological control activity against plant pathogens. This study aimed to explore the potential of purified fengycin to induce systemic resistance in tomato against Sclerotinia sclerotiorum. Bacillus amyloliquefaciens FZB42, its mutant AK1S, and their corresponding metabolites showed in vitro inhibition of S. sclerotiorum mycelium. Fengycin derived from an AK1S mutant was purified and identified through HPLC and MALDI-TOF-MS, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed structural deformities in the fungal mycelium. Moreover, fengycin induced the accumulation of reactive oxygen species (ROS) in S. sclerotiorum mycelium and downregulated the expression of ROS-scavenging genes viz., superoxide dismutase (SsSOD1), peroxidase (SsPO), and catalase (SsCAT1) compared to the untreated control. Furthermore, the lesion size was dramatically reduced in fengycin-treated tomato plants compared to plants infected with S. sclerotiorum only in a greenhouse experiment. Additionally, the transcriptional regulation of defense-related genes GST, SOD, PAL, HMGR, and MPK3 showed the highest upsurge in expression at 48 h post-inoculation (hpi). However, their expression was subsequently decreased at 96 hpi in fengycin + S. sclerotiorum treatment compared to the plants treated with fengycin only. Conversely, the expression of PPO increased in a linear manner up to 96 hpi.

Highlights

Biological control has emerged as the most effective, environment-friendly, and non-toxic option to control several plant pathogens [1,2]
The results of our study demonstrated that fengycin was perceived by the plants as a defense elicitor and induced induced systemic resistance (ISR) in tomato plants against S. sclerotiorum by upregulating the expression of genes involved in defense-related pathways
Our study revealed the possible mechanism of action of fengycin and elucidated the specific role of fengycin in the elicitation of ISR in tomato plants against S. sclerotiorum

Summary

Introduction

Biological control has emerged as the most effective, environment-friendly, and non-toxic option to control several plant pathogens [1,2]. Bacillus species are potential biological control agents against multiple soil-borne plant pathogens [3]. Bacillus species are considered as antimicrobial compound-manufacturing factories [4] with the potential to produce several broad-spectrum antifungal secondary metabolites [5,6]. A genome analysis of B. amyloliquefaciens FZB42 has revealed 10 gene clusters, covering approximately 10% of the whole genome, that are responsible for manufacturing secondary metabolites with strong antimicrobial activity. Among these secondary metabolites, cyclic lipopeptides are the most significant

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