THE 24-KDA PROTEIN FROM FUSARIUM-OXYSPORUM F-SP ERYTHROXYLI - OCCURRENCE IN RELATED FUNGI AND THE EFFECT OF GROWTH-MEDIUM ON ITS PRODUCTION

A 24-kDa protein that elicits ethylene production and necrosis in leav es of dicotyledonous plants was previously purified from culture filtr ates of Fusarium oxysporum Schlechtend:Fr. f.sp. erythroxyli. Antisera to the denatured 24-kDa protein detected 2.5 ng of the 24-kDa protein on Western blots at 100 000-fold dilutions. The antisera cross-reacte d with a 24-kDa protein on Western blots of culture filtrates from thr ee other F. oxysporum formae speciales. Of seven Fusarium species, onl y F. oxysporum, F. acuminatum Ellis and Kellerm., and F. avenaceum (Fr .:Fr.) Sacc. isolates produced an antigenically related 24-kDa protein . Although there were differences in the profiles of proteins extracte d from stems of coca (Erythroxylum coca var. coca L. Lam.) infected wi th F. oxysporum f.sp. erythroxyli compared with uninfected stems, anti sera to the 24-kDa protein did not cross-react with any proteins from the infected coca stems. For the fungal isolates studied, the best med ium tested for production of the 24-kDa protein contained 1% sucrose a nd 1% asparagine. Biological activity of the F. oxysporum culture filt rates on sweet basil leaves was consistently correlated with the prese nce of the 24-kDa protein. Production of the 24-kDa protein was limite d in cultures containing pectin or cellulose as the primary carbon sou rce, or in cultures lacking sucrose or casamino acids. Water-soluble e xtracts from coca stems inhibited production of the 24-kDa protein, wh ereas cellulose and pectin did not. Components produced by the plant m ay limit production of the 24-kDa protein in infected plant tissue and thereby limit the response of the plant to the fungus. These results suggest the 24-kDa protein does not function in the symptomatic phase of the F. oxysporum f.sp. erythroxyli - coca disease interaction.