The role of zinc in regulating tabtoxin production

Summary The phytotoxin, tabtoxinine--lactam, is produced by severalPseudomonas syringae pathovars if adequate Zn is available, otherwise its biologically inactive form, tabtoxin, is produced. The Zn is required for the action of a peptidase which cleaves tabtoxin, releasing the toxic -lactam.This research was supported in part by U.S.D.A. Competitive Research Grant No. 83-CRCR-1-1201.     

Reciprocal biological activities of the cyclic tetrapeptides chlamydocin and HC-toxin

Summary Chlamydocin, a potent cytostatic agent against cultured mammalian cells, and HC-toxin, a host-specific phytotoxin, are cyclic tetrapeptides containing the same epoxide -amino acid. We show here that these compounds have reciprocal biological activity; HC-toxin is cytostatic against cultured mastocytoma cells, and chlamydocin has host-specific toxin activity against maize. Chlamydocin and another related cyclic peptide, Cyl-2, are less host-specific than HC-toxin because maize tolerant to HC-toxin is more sensitive to chlamydocin and Cyl-2.     

Fijiensin,the first phytotoxin fromMycosphaerella fijiensis,the causative agent of Black Sigatoka disease

Summary Fijiensin, a novel phytotoxic metabolite, was isolated from a culture of the fungusMycosphaerella fijiensis, the causal agent of Black Sigatoka disease of banana. Fijiensin is phytotoxic on various banana cultivars, but not toward non-host plants. The structure of fijiensin was determined by X-ray analysis.     

Isolation and partial characterization of a phytotoxic glycoprotein from culture filtrates ofRhynchosporium secalis

Summary Rhynchosporium secalis (Oud.) Davis produces a phytotoxic compound with a mol. wt of 275×10³ which is able to induce chlorotic symptoms in both susceptible and resistant barley leaves. Collectively, the data suggest that the toxin is a glycoprotein. Mild base treatment, by elimination, indicates that threonine and serine are involved in o-glycosidic linkages with the carbohydrate moiety. Sugar residues occur in the molecule in the ratio of mannose, rhammnose, galactose, glucosamine 13.6111.Acknowledgments. We acknowledge the assistance of Mr M. McNeil and P. Albersheim in doing the sugar analyses shown in this report. Financial support for this project was provided by a BARD grant 1-31-79, the French government, and the Montana Ag. Expt. Station.