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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.