Polyamines metabolism during the germination of Sclerotinia sclerotiorum ascospores and its relationship with host infection

GÁRRIZ, ANDRÉS; DALMASSO, MARÍA C; MARINA, MARÍA; RIVAS, ELISA I; RUIZ, OSCAR A; PIECKENSTAIN, FERNANDO L

NEW PHYTOLOGIST

Blackwell

Año: 2004 vol. 161 p. 847 - 854

0028-646X

        Polyamine biosynthesis inhibitors were used to study the role of polyamine metabolism during the germination of Sclerotinia sclerotiorum ascospores, and to carry out a preliminary evaluation of the potential of polyamine biosynthesis inhibition for the control of ascospore-borne diseases on plant hosts.        Inhibitors were added to the germination medium and ascospore germination, free polyamine levels and ornithine decarboxylase activity were determined. Development of disease symptoms on tobacco (Nicotiana tabacum) leaf discs inoculated with ascospores after treatment with the inhibitors was also evaluated.        Difluoromethylornithine inhibited ornithine decarboxylase and decreased free spermidine levels but had no effect on ascospore germination when used at concentrations lower than 10 mM. Both, the spermidine synthase inhibitor cyclohexylamine and the S-adenosyl-methionine decarboxylase inhibitor methylglyoxal bis-[guanyl hydrazone] decreased free spermidine levels, but only the latter inhibited ascospore germination, at concentrations of 5 mM or higher. Dormant ascospores contained higher polyamine levels than mycelium. Lesion development on leaf discs was reduced by cyclohexylamine and methylglyoxal bis-[guanyl hydrazone], but not by difluoromethylornithine.         Ascospore germination does not depend on ornithine decarboxylase activity and inhibitors of this enzyme will probably have a limited potential for the control of ascospore-borne plant diseases. On the contrary, spermidine synthase and S-adenosyl-methionine decarboxylase could be more suitable targets for fungicidal action. The relative insensitivity of ascospore germination to polyamine biosynthesis inhibitors may be due to the high content of free polyamines in dormant ascospores.