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Biochemistry and Cell Biology

Respiratory Characteristics in Pyricularia oryzae Exposed to a Novel Alkoxyiminoacetamide Fungicide. A. Mizutani, Aburahi Laboratories, Shionogi Co., Ltd., 1405 Gotanda, Koka-cho, Koka-gun Shiga 520-34 Japan; H. Yukioka, H. Tamura, N. Miki, M. Masuko, and R. Takeda. Aburahi Laboratories, Shionogi Co., Ltd., 1405 Gotanda, Koka-cho, Koka-gun Shiga 520-34 Japan. Phytopathology 85:306-311. Accepted for publication 28 November 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-306.

(E)-2-Methoxyimino-N-methyl-2-(2-phenoxyphenyl) acetamide (SSF-126) inhibited respiration of Pyricularia oryzae mycelia by blockade of the electron flux through the cytochrome bc1 segment of the mitochondrial respiratory chain. However, the mycelia again began to respire at 20 min after treatment. The recovered respiration was sensitive to salicylhydroxamic acid, a potent inhibitor of cyanide-resistant respiration, but not to potassium cyanide, indicating that SSF-126 had the ability to induce cyanide-resistant respiration in P. oryzae. The recovered respiration was partially linked to energy transduction because SSF-126 could not completely suppress the mycelial growth. SSF-126 caused a rapid depletion of ATP content, but the ATP levels showed recovery, resulting in improvement of energy charge values. However, the total adenylate pool gradually decreased, resulting in only 60% remaining 48 h after treatment. SSF-126 markedly suppressed the mycelial growth, the duration for mass doubling in cultures incubated with SSF-126 being 2.4 times that in the control ones. Thus, SSF-126 works deleteriously on the supply of metabolic energy in P. oryzae.

Additional keywords: adenine nucleotide, complex III, mitochondria, oxidative phosphorylation, submitochondrial particles.