This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (34) Citing Articles via Google Scholar Google Scholar Articles by Bednarski, M. A. Articles by Scheffer, R. P. Search for Related Content PubMed PubMed Citation Articles by Bednarski, M. A. Articles by Scheffer, R. P. Agricola Articles by Bednarski, M. A. Articles by Scheffer, R. P.

Articles

Reversible Effects of Toxin from Helminthosporium maydis Race T on Oxidative Phosphorylation by Mitochondria from Maize ^1,2

^a Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan 48824

Host-selective toxin from Helminthosporium maydis race T inhibited oxidative phosphorylation (AT³²P formation) and stimulated ATPase activity by mitochondria from male-sterile (T) but not from normal (N) cytoplasm maize (Zea mays L.). Toxin increased the rate of NADH oxidation, but succinate oxidation was slightly, and malate-pyruvate oxidation was strongly inhibited as the associated ATP formation was abolished. There was a 1-minute lag before toxin gave maximal stimulation of NADH oxidation; the responses to 2,4-dinitrophenol and valinomycin were immediate. There was also a delay in the effect of toxin on ATP formation. T mitochondria were more sensitive than were N mitochondria to uncoupling by nigericin plus K⁺; there was no evidence, however, that the action of toxin is related to that of nigericin or other ionophores. With NADH as the substrate, the degree of uncoupling increased with increases in toxin concentration up to a saturating level; kinetics of the response suggested reversibility. T mitochondria exposed to toxin for 5 minutes regained normal rates of respiration and of ATP formation when they were washed with toxin-free medium, showing that the uncoupling effect is reversible. Evidently HM-T toxin does not bind firmly to its site(s) of action, in contrast to reports for another hostselective toxin.

⁴ Present address: Department of Biology, Wayne State University, 410 W. Warren St., Detroit, Mich. 48202.

¹ Supported by National Science Foundation Grants GB-24962 and GB-37959.

² Journal Article No. 7757, Michigan Agricultural Experiment Station.

This article has been cited by other articles:

				R. P. Scheffer and R. S. Livingston Host-Selective Toxins and Their Role in Plant Diseases Science, January 6, 1984; 223(4631): 17 - 21. [Abstract] [PDF]