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Title: Preillumination of rice blast conidia induces tolerance to subsequent oxidative stress

item AVERYANOV, ANDREY - Russian Institute Of Phytopathology
item LAPIKOVA, VERA - Russian Institute Of Phytopathology
item PASECHNIK, TATIANA - Russian Institute Of Phytopathology
item ABRAMOVA, OLGA - Russian Institute Of Phytopathology
item GAIVORONSKAYA, LUDMILLA - Russian Institute Of Phytopathology
item KUZNETSOV, VLADIMIR - Russian Institute Of Phytopathology
item Baker, Con

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2014
Publication Date: 12/1/2014
Citation: Averyanov, A.A., Lapikova, V.P., Pasechnik, T.D., Abramova, O.S., Gaivoronskaya, L.M., Kuznetsov, V., Baker, C.J. 2014. Preillumination of rice blast conidia induces tolerance to subsequent oxidative stress. Fungal Biology. 118:743-753.

Interpretive Summary: Fungal diseases of crops cause major losses for farmers each year. The first step is the germination of the fungal spore on the leaf surface. By learning to disrupt critical mechanisms that are involved in spore germination we could reduce the amount of disease. This study demonstrates the role that light can play in protecting fungal spores from reactive oxygen released by the plant. The study investigates conditions that might oppose this ‘light protection’ of the spores and thereby prevent disease. This information will be of use to plant scientists who are devising new strategies to improve disease resistance in plants.

Technical 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-hour and, to larger extent, 5-hour illumination. The effect was diminished by antioxidants and, therefore, suggests involve ment 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 H2O2, O2 -, or OH or to toxic diffusates 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 H2O2 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.