The binding of host-selective toxin analogs to mitochondria from normal and 'Texas' male sterile cytoplasm maize

• Published in: Plant physiology (Bethesda) Vol. 83; no. 4; pp. 863 - 868
• Main Authors: Frantzen, K.A, Daly, J.M, Knoche, H.W
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.04.1987
• Subjects: Biological and medical sciences; CITOPLASMA; COCHLIOBOLUS; COCHLIOBOLUS HETEROSTROPHUS; Corn; CYTOPLASM; CYTOPLASME; ESTERILIDAD MASCULINA; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Helminthosporium; Ligands; MALE INFERTILITY; MITOCHONDRIA; MITOCHONDRIE; MITOCONDRIA; MYCOSPHAERELLA; MYCOSPHAERELLA ZEAE-MAYDIS; Oxidation; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Radioactive decay; Receptors; Respiration; STERILITE MALE; TOXINAS; TOXINE; TOXINS; ZEA MAYS; Binding; Monocotyledones; Zea mays; Mycosis; Bipolaris maydis; Host specificity; Vegetal microorganism relation; Molecular interaction; Host agent relation; Phytopathogen; Biological activity; Cereal crop; Fungi; Infection; Toxin; Mitochondria; Structure activity relation; Gramineae; Angiospermae; Male sterility; Spermatophyta; Fungi Imperfecti; Thallophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.83.4.863

Tritium-labeled toxin analogs were prepared by reduction with NaB3H4 of either the toxin from Helminthosporium maydis race T or a toxin component from Phyllosticta maydis. These reduced analogs had high radiochemical specific activities, high biological activities, and plant specificities identical to the native toxins. A filtration assay was developed to test the binding of these labeled analogs to isolated mitochondria. Binding was not energy dependent nor was there measurable matrical uptake. The analogs were shown to be lipophilic, a characteristic which gave rise to considerable nondisplaceable binding. Under conditions limiting nondisplaceable binding, the displaceable binding was shown to be linear with respect to toxin concentration and unsaturable. No significant differences were observed in the binding characteristics between the mitochondria from normal and male-sterile (Texas) cytoplasm maize. The findings suggest that, at physiologically relevant concentrations, these toxin analogs permeate the membranes of susceptible and resistant mitochondria alike. The lack of demonstrable specific binding does not rule out the involvement of a classical receptor site but does indicate that other kinds of molecular interactions may be involved in the mechanisms for toxicity and specificity.