title: Pre-illumination of rice blast conidia induces tolerance to subsequent oxidative stress.
abstract: Many environmental factors, alone or combined, affect organisms by changing a pro-/antioxidant balance. Here we tested rice blast fungus (Magnaporthe oryzae) for possible cross-adaptations caused by relatively intense light and protecting from artificially formed reactive oxygen species (ROS) and ROS-dependent fungitoxic response of the host plant. Spore germination was found to be suppressed under 4-h and, to larger extent, 5-h illumination. The effect was diminished by antioxidants and, therefore, suggests involvement of ROS. One-hour of light did not affect spore germination, but stimulated their chemically assayed superoxide production. The illuminated spores were more tolerant (than non-illuminated ones) to artificially generated H(2)O(2), O(2)(-), or OH or to toxic diffusate of rice leaf. They also caused more severe disease symptoms if applied to leaves of the susceptible rice cultivar at low concentration. Spore diffusates decomposed hydrogen peroxide. They detoxified exogenous H(2)O(2) and superoxide radical as well as leaf diffusates. Spore illumination increased some of these protective effects. It is suggested that short-term light led to mild oxidative stress, which induced spore antioxidant capacity, enhancing spore tolerance to subsequent stronger oxidative stress and its aggressiveness in planta. Such tolerance depends partly on the antidotal action of spore extracellular compounds, which may also be light-stimulated. Therefore, a certain ROS-related environmental factor may adapt a fungus to other factors and so modulate its pathogenic properties.
authors.affiliation: Research Institute of Phytopathology, B. Vyazemy, Moscow Region 143050, Russia. Electronic address: andrey.a.averyanov@yandex.ru.
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Aver'yanov
authors.affiliation: Research Institute of Phytopathology, B. Vyazemy, Moscow Region 143050, Russia.
authors.forename: Vera P
authors.initials: VP
authors.lastname: Lapikova
authors.affiliation: Research Institute of Phytopathology, B. Vyazemy, Moscow Region 143050, Russia.
authors.forename: Tatiana D
authors.initials: TD
authors.lastname: Pasechnik
authors.affiliation: Russian People's Friendship University, 8 M. Maklay Str., Moscow 117813, Russia.
authors.forename: Olga S
authors.initials: OS
authors.lastname: Abramova
authors.affiliation: Russian People's Friendship University, 8 M. Maklay Str., Moscow 117813, Russia.
authors.forename: Ludmilla M
authors.initials: LM
authors.lastname: Gaivoronskaya
authors.affiliation: Russian People's Friendship University, 8 M. Maklay Str., Moscow 117813, Russia.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Kuznetsov
authors.affiliation: Agricultural Research Service USDA, Beltsville, MD 20705, USA.
authors.forename: C Jacyn
authors.initials: CJ
authors.lastname: Baker
mesh_terms: D004361:Drug Tolerance; D008027:Light; D020082:Magnaporthe / Q000502:physiology* / Q000528:radiation effects*; D012275:Oryza / Q000382:microbiology; D016877:Oxidants / Q000633:toxicity; D018384:Oxidative Stress; D010935:Plant Diseases / Q000382:microbiology; D013172:Spores, Fungal / Q000502:physiology* / Q000528:radiation effects*
chemical_list: D016877:Oxidants
keywords: Antioxidant capacity; Fungitoxicity; Light; Oxidative stress; Rice blast spores