The Effects of Light and Photo‐ and Protein‐synthetic Inhibitors on the Sekiguchi Lesion Formation by Magnaporthe grisea in Rice cv. Sekiguchi‐asahi*

Abstract

The significance of light irradiation in Sekiguchi lesion (SL) formation by infection with Magnaporthe grisea on rice cv. Sekiguchi-asahi was investigated. When the leaf blades of cv. Sekiguchi-asahi inoculated with M. grisea spores were kept under different wavelengths of light. SLs were formed under visible light regardless of the compatibility between fungal race and cv. Sekiguchiasahi. On the contrary, typical blast and or nectrotic spot lesions were formed under near ultraviolet radiation from the black light fluorescent lamps and near infrared radiation from infrared fluorescent lamps. The effective wavelength for light-dependent SL formation was 400-700 nm. Furthermore,thelongerthe wavelength of radiation, the bigger were the SLs. Such light-dependent induction of the SL was suppressed by pretreatment of 3-(3,4-dichlorophenyl)-l ,1-dimethylurea (DCMU) and cycloheximide (CY). These results suggested that photosynthetic and protein synthetic activities were involved in SL formation. Zusammenfassung Die Einfliisse des Lichtes sowie Photo-und ProteinsyntheseInhibitoren auf die Bildung von "Sekiguchi-Lasionen" durch Magnaporthe grisea in Reis der Sorte Sekiguchi-asahiUntersucht wurde die Bedeutung des Lichtes bei der Bildung von "Sekiguchi-Lasionen" (SL) bei der Reissorte Sekiguchi-asahi nach einer Infektion mit Magnaporthe grisea. Nach einer M. grrw^a-Inokulation von Blattern der Sorte Sekiguchi-asahi, die bei unterschiedlichen Lichtwellenlangen anschlieBend inkubiert worden waren, wurden SLs im sichtbarem Lichtbereich gebildet, unabhangig von der Kompitabiitat der Pilzrasse mit der Sorte Sekiguchi-asahi. Im Gegensatz dazu wurden fypische *This study is part 13 in series. Studies oti host-selective infection mechanism of Magnaporthe grisea (Hebert) Barr. atid was supported in part by Grant-in-aid for Research (Nos. 07660058 and 08660057) from the Ministry of Education. Science and Culture of Japan.Reisbrandflecken und/oder nekrotische Lasionen unter Nah-UV-Licht ("Schwarzlicht") bzw. Nah-InfrarotLicht gebildet. Die wirksame Wellenlange fur eine lichtabhangige SL-Bildung lag zwischen 400 und 700 nm. Es wurde auBerdem beobachtet, dafl je langer die Bestrahlungswellenlange, desto grofler die SLs waren. Diese lichtabhangige Induktion der SL-Bildung konnte durch eine Vorbehandlung mit 3-(3,4-Dichlorophenyl)-1,1 -Dimethylharnstoff (DCMU) sowie mit Cycloheximid (CY) unterdriickt werden. Diese Ergebnisse deuten daraufhin, daB sowohl photosynthetische als auch proteinsynthetishche Aktivitaten mit der SL-Bildung gekoppelt sind. IntroductionMagnaporthe grisea (Hebert) Barr (= Pyricularia oryzae Cavara) is the pathogen of rice blast disease which is one of the most important plant diseases in Japan. Resistance and susceptibility of rice plants to M. grisea are determined by the interaction between fungal race and rice cultivar (Yamada et al., 1976). When M. grisea infects rice leaves, it forms lesions which are brown and typically elliptical with more or less pointed ends. However, the mutant rice cv. Sekiguchi-asahi, whi...

Genetic and molecular characterization of a blue light photoreceptor MGWC-1 in Magnaporth oryzae

“…In addition, the authors reported that phytochrome (red-light receptor) is responsible for the systemic acquired resistance. In rice plant, pathogen-induced defense responses are influenced by light conditions (Arase et al, 1997;Guo et al, 1993;Park et al, 2000). Effects of light on pathogen physiology are far less understood.…”

Topology, Subcellular Localization, and Sequence Diversity of the Mlo Family in Plants

“…Examples are the Arabidopsis lsd1 and edr1 mutants, each exhibiting resistance to both virulent bacterial and fungal pathogens (3,4). In rice, the sl mutant confers resistance to the rice blast fungus, Magnaporthe grisea (5). Similarly, the barley mlo mutant confers broad spectrum resistance to the powdery mildew fungus, Erysiphe graminis f.sp.…”

DNA fragmentation in Sekiguchi lesion mutants of rice infected with Magnaporthe grisea

“…Although Sekiguchi lesion formation in the light is a resistant response of sl mutants to M. grisea infection, blast lesion formation in the dark is a susceptible response (Arase et al 1997). To elucidate the mechanism underlying the light-enhanced resistance of the sl mutants to M. grisea infection, DNA fragmentation and DNase activity involved in the cell death induction were investigated.…”

“…Sekiguchi lesions were induced in leaves of the sl mutant inoculated with M. grisea spores under visible light (400-700 nm), whereas blast lesions were induced in the dark or under near-ultraviolet (UV) light (290-330 nm) (Arase et al 1997). Furthermore, infection hypha formation and sporulation of M. grisea were significantly inhibited in the Sekiguchi lesions.…”