Polyamine metabolism during the germination of Sclerotinia sclerotiorum ascospores and its relation with host infection

ANDRÉS GÁRRIZ, MARÍA C. DALMASSO, MARÍA MARINA, OSCAR A. RUIZ & FERNANDO L. PIECKENSTAIN†.

NEW PHYTOLOGIST

Año: 2004 vol. 161 p. 847 - 854

0028-646X

Polyamine biosynthesis inhibitors were used to study polyamine metabolism during the germination of Sclerotinia sclerotiorum ascospores, and to evaluate of the potential of polyamine biosynthesis inhibition for the control of ascospore-borne diseases on plant hosts. The effect of inhibitors on ascospore germination, free polyamine levels, ornithine decarboxylase activity and development of disease symptoms on tobacco (Nicotiana tabacum) leaf discs inoculated with ascospores were determined. alfa-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-[guanylhydrazone] 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 alfa-difluoromethylornithine. Ascospore germination did 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 their high polyamine content.