Transcriptional Profiling of Diffusible Lipopeptides and Fungal Virulence Genes During Bacillus amyloliquefaciens EZ1509-Mediated Suppression of Sclerotinia sclerotiorum

Abstract

Sclerotinia sclerotiorum is a devastating necrotrophic pathogen that infects multiple crops, and its control is an unremitting challenge. In this work, we attempted to gain insights into the pivotal role of lipopeptides (LPs) in the antifungal activity of Bacillus amyloliquefaciens EZ1509. In a comparative study involving five Bacillus strains, B. amyloliquefaciens EZ1509 harboring four LPs biosynthetic genes (viz. surfactin, iturin, fengycin, and bacilysin) exhibited promising antifungal activity against S. sclerotiorum in a dual-culture assay. Our data demonstrated a remarkable upsurge in LPs biosynthetic gene expression through quantitative reverse transcription PCR during in vitro interaction assay with S. sclerotiorum. Maximum upregulation in LPs biosynthetic genes was observed on the second and third days of in vitro interaction, with iturin and fengycin being the highly expressed genes. Subsequently, Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry analysis confirmed the presence of LPs in the inhibition zone. Scanning electron microscope analysis showed disintegration, shrinkage, plasmolysis, and breakdown of fungal hyphae. During in planta evaluation, S. sclerotiorum previously challenged with EZ1509 showed significant suppression in pathogenicity on detached leaves of tobacco and rapeseed. The oxalic acid synthesis was also significantly reduced in S. sclerotiorum previously confronted with antagonistic bacterium. The expression of major virulence genes of S. sclerotiorum, including endopolygalacturonase-3, oxalic acid hydrolase, and endopolygalacturonase-6, was significantly downregulated during in vitro confrontation with EZ1509.

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

“…Antibiosis is the main mechanism of biological control that has been well-studied genetically and biochemically [35]. In recent years, several studies have reported the inhibition of fungal pathogens by cyclic lipopeptides [6,37,38]. The excretion of antimicrobial compounds by Bacillus species is the primary cause of the formation of fungal growth inhibition zones in dual culture [39].…”

Novel Genetic Dysregulations and Oxidative Damage in Fusarium graminearum Induced by Plant Defense Eliciting Psychrophilic Bacillus atrophaeus TS1

“…A mycelial plug of 0.6 cm from fungus grown for 4 days was patched in the center of PDA medium plates and 5 µL of each bacterial suspension with optical density (OD) of 2.50 (at 600 nm) was inoculated 3 cm away from the patched mycelium. Sterilized LB media was also used in the same plate as control [7]. The plates were incubated at 25 • C and 15 • C for 4 days to observe the fungal inhibition zone at optimal growth temperature as well as at cold conditions.…”

“…are reported to be the most efficient biocontrol agents. These bacteria have the ability to survive and colonize complex environments and to produce a wide range of antifungal extracellular enzymes as well as antimicrobial secondary metabolites including lipopeptides (LPs) [6,7]. Bacillus can produce multiple low molecular-weight, amphiphilic, antimicrobial compounds synthesized by non-ribosomal peptide synthetase (NRPS) enzyme-complexes such as surfactin, iturins, and fengycin [8,9].…”

Combining Desirable Traits for a Good Biocontrol Strategy against Sclerotinia sclerotiorum

“…Among iturins, iturin A and C, bacillomycin D, F, L, LC, and mycosubtiline are the main variants of this chemical family that increase membrane permeability and therefore display strong antifungal activity [37]. This antifungal activity is based on the formation of pores in the fungal cell membranes that cause an osmotic imbalance, membrane disruption, and solubilization [51]. The antimicrobial effect of fengycin is high, especially against filamentous fungi [51], as this molecule interacts with the membrane lipid bilayer.…”

“…This antifungal activity is based on the formation of pores in the fungal cell membranes that cause an osmotic imbalance, membrane disruption, and solubilization [51]. The antimicrobial effect of fengycin is high, especially against filamentous fungi [51], as this molecule interacts with the membrane lipid bilayer. It causes its solubilization, modifies its structure and permeability, and creates ion-conducting channels that pass through it [37,51].…”