Polyamine Biosynthetic Enzymes and the Effect of their Inhibition on the Growth of Some Phytopathogenic Fungi

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Studies were conducted on the distribution of two polyamine biosynthetic enzymes, ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), and the effect of their inhibitors on growth and polyamine biosynthesis in four phytopathogenic fungi, namely, Helminthosporium maydis, H. carbonum, Fusarium oxysporum f. sp. lycopersici and Ceratocystis ulmi. Three species had high level of ODC as compared to ADC activity; in C. ulmi on the other hand, ADC was predominant with very little or no ODC activity. DL-a-difluoromethylornithine (DFMO) significantly inhibited ODC activity in all species in vitro with little effect on ADC activity. ADC in all cases was inhibited by DL-a-difluoromethylarginine (DFMA) but not by DFMO. Mycelial growth of all fungi was inhibited by 1 to 5 mM concentrations of either DFMO or DFMA within two days except in H. maydis which remained unaffected even by the highest concentration (5 mM) of DFMA. In general, the inhibition was more pronounced with DFMO as compared to DFMA. Putrescine completely reversed the inhibitory effects of DFMO and DFMA in all species. Among the polyamines, spermidine was predominant in all fungi. The cellular concentrations of putrescine and spermidine were considerably lower in the presence of either of the inhibitors while spermine levels were higher than the control.
日本植物生理学会の論文