Root Defense Responses to Fungal Pathogens: A Molecular Perspective

Abstract

This review will focus on the molecular and genetic mechanisms underlying defense responses of roots to fungal pathogens. Soil-borne pathogens, including Phytophthora, Pythium, Fusarium, and Bipolaris, represent major sources of biotic stress in the rhizosphere and roots of plants. Molecular recognition and signaling leading to effective resistance has been demonstrated to occur between host and Phytophthora, or Pythium. The hypersensitive response and apoptotic cell death, two oxidative processes that limit biotrophic pathogens, generally act to exacerbate disease symptoms induced by necrotrophic organisms. Although pathogenesis-related proteins can be expressed in roots during pathogen challenge, salicylic acid has not been implicated in root-mediated interactions. Jasmonic acid and ethylene have been found to mediate parallel as well as synergistic pathways that confer partial tolerance to necrotrophic pathogens, as well as induced systemic resistance to root and foliar pathogens. Genomics approaches are revealing new networks of defense-signaling pathways, and have the potential of elucidating those pathways that are important in root-defense responses.Abbreviations: CEVI -constitutive expression of VSPI (vegetative storage protein 1); COI1 -coronatineinsensitive 1; E -ethylene; EDS -enhanced disease susceptibility; EIN -ethylene-insensitive; ERF1ethylene response factor 1; ETR -ethylene resistant; fad -fatty acid desaturation; Ggt -Gaeumannomyces graminis var. tritici; HR -hypersensitive response; LRR -leucine-rich repeat protein motif; JA -jasmonic acid/jasmonate; NBS -nucleotide binding site protein motif; PR -pathogenesis-related; ROS -reactive oxygen species; SA -salicylic acid/salicylate; TLP thaumatin-like protein; PR-5 * FAX No: +1-509-335-7674.

Fusarium wilt of banana: biology, epidemiology and management

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More beneath the surface? Root versus shoot antifungal plant defenses

“…As if handling abiotic stress would not be already a substantial task, roots are also garrisoned at the frontline against pathogens and pests. Soil-borne pathogens such as Fusarium , Pythium , or Phytophthora are infamous for being vicious parasites that can devastate entire harvests (Okubara and Paulitz, 2005). However, the lack of a convenient accessibility of root systems renders the task of controlling such pathogens more than challenging.…”

Defense Proteins from Vigna Unguiculata Seed Exudates: Characterization and Inhibitory Activity Against Fusarium Oxysporum

“…Germinating seeds and roots release compounds that may interfere with the development of surrounding microorganisms (Nobrega et al 2005;Okubara and Paulitz 2005). Several compounds exuded from seeds were identified and some of them have the ability to inhibit pathogen growth, thus preventing seed infection, and others have direct beneficial effects on the germination itself (Barbour et al 1991).…”