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

GÁRRIZ A, MC DALMASSO, M MARINA, EI RIVAS, OA RUIZ & FL PIECKENSTAIN

NEW PHYTOLOGIST

SpringerLink

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 the potential of polyamine biosynthesis inhibition for the control of ascospore-borne diseases in plants. • The effects 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. •α-Difluoromethylornithine inhibited ornithine decarboxylase and decreased free spermidine levels, but had no effect on ascospore germination. Both, the spermidine synthase inhibitor cyclohexylamine and the S-adenosyl-methionine decarboxylase inhibitor methylglyoxalbis-[guanyl hydrazone] decreased free spermidine levels, but only the latter inhibited ascospore germination, at concentrations of 5 mM or higher. Lesion development on leaf discs was reduced by cyclohexylamine and methylglyoxalbis-[guanyl hydrazone], but not byá-difluoromethylornithine. In the absence of inhibitors, dormant ascospores contained higher polyamine levels than mycelium. • 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-adenosylmethionine decarboxylase could be more suitable targets for fungicidal action. The relative insensitivity of ascospore germination to polyamine biosynthesis inhibitors may be caused by their high polyamine content.