Polyamine metabolism during germination of Sclerotinia sclerotiorum ascospores

GARRIZ A, C DALMASSO, M MARINA, A KHOMUTOV, OA RUIZ, FL PIECKENSTAIN

Garriz A, C Dalmasso, M Marina, A Khomutov, OA Ruiz, FL Pieckenstain

Congreso; XXXVIII Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas; 2001

Fungal morphogenesis has been associated with changes in polyamine metabolism and the potencial of biosynthesis inhibitors as fungicides has been demonstrated. The fungus Sclerotinia sclerotiorum is the most important pathogen of sunflower in Argentina. We have previously shown that micelial growth (MG), sclerotial development (SD) and ascospores germination (AG) differ in their sensitivities to polyamine biosynthesis inhibitors, AG being insensitive to inhibitor concentrations up to 1 mM. In this work, we studied the effect of higher concentrations of inhibitors on AG, to explore the basis for AG insensitivity to inhibitors. We also evaluated the effect of 1-aminooxy-3-aminopropane (APA), an inhibitor of mammalian and bacterial ornithine decarboxylase (ODC), spermidine synthase (Spd Synt) and S-adenosyl-methionine decarboxylase (AdoMet DC). AG was more sensitive to Spd Synt and Ado Met DC inhibitors than to ODC inhibitors. Thus, spermidine level (or alternatively spermidine/putrescine ratio) seems to be critical for this differenciation process, as previously reported by us in relation to SD. APA strongly inhibited ODC and Spd Synt activities, as well as AG. Addicional data on the effect of APA on polyamine biosynthesis in S. sclerotiorum wil be presented. To our knowledge, this is the first report on the effect of APA on polyamine biosynthesis enzymes in fungi.