title: Induced systemic resistance responses in perennial ryegrass against Magnaporthe oryzae elicited by semi-purified surfactin lipopeptides and live cells of Bacillus amyloliquefaciens.
abstract: The suppressive ability of several strains of cyclic lipopeptide-producing Bacillus rhizobacteria to grey leaf spot disease caused by Magnaporthe oryzae has been documented previously; however, the underlying mechanism(s) involved in the induced systemic resistance (ISR) activity in perennial ryegrass (Lolium perenne L.) remains unknown. Root-drench application of solid-phase extraction (SPE)-enriched surfactin and live cells of mutant Bacillus amyloliquefaciens strain FZB42-AK3 (produces surfactin, but not bacillomycin D and fengycin) significantly reduced disease incidence and severity on perennial ryegrass. The application of the treatments revealed a pronounced multilayered ISR defence response activation via timely and enhanced accumulation of hydrogen peroxide (H2O2), elevated cell wall/apoplastic peroxidase activity, and deposition of callose and phenolic/polyphenolic compounds underneath the fungal appressoria in naïve leaves, which was significantly more intense in treated plants than in mock-treated controls. Moreover, a hypersensitive response (HR)-type reaction and enhanced expression of LpPrx (Prx, peroxidase), LpOXO4 (OXO, oxalate oxidase), LpPAL (PAL, phenylalanine ammonia lyase), LpLOXa (LOX, lipoxygenase), LpTHb (putative defensin) and LpDEFa (DEFa, putative defensin) in perennial ryegrass were associated with SPE-enriched surfactin and live AK3 cell treatments, acting as a second layer of defence when pre-invasive defence responses failed. The results indicate that ISR activity following surfactin perception may sensitize H2O2 -mediated defence responses, thereby providing perennial ryegrass with enhanced protection against M. oryzae.
authors.affiliation: Department of Plant Pathology and Environmental Microbiology, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Alamgir
authors.initials: A
authors.lastname: Rahman
authors.affiliation: Department of Plant Pathology and Environmental Microbiology, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Wakar
authors.initials: W
authors.lastname: Uddin
authors.affiliation: Department of Plant Pathology and Environmental Microbiology, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Nancy G
authors.initials: NG
authors.lastname: Wenner
mesh_terms: D001407:Bacillus / Q000502:physiology*; D017343:Genes, Plant; D055666:Lipopeptides / Q000502:physiology*; D008129:Lolium / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D020082:Magnaporthe / Q000502:physiology*; D010456:Peptides, Cyclic / Q000502:physiology*
chemical_list: D055666:Lipopeptides; D010456:Peptides, Cyclic; C009365:surfactin peptide
keywords: H2O2 accumulation; hypersensitive response; peroxidase activity; real-time RT-PCR; solid-phase extraction (SPE)