ACTION OF THE MELANIN BIOSYNTHESIS INHIBITORS, FTHALIDE AND TRICYCLAZOLE, ON APPRESSORIAL PENETRATION BY PYRICULARIA ORYZAE

摘要

Inhibitors of polyketide melanin biosynthesis and intermediates from this biosynthetic pathway were studied to determine their influence on the capacity of appressoria of Pyricularia oryzae to penetrate onion epidermal cell walls. Cerulenin, an inhibitor of fatty acid and polyketide biosynthesis was used to block the formation of cyclized intermediates of the melanin biosynthetic pathway in appressoria of both the wild type P. oryzae P-2 and the buff mutant P-2 m-1. When treated with 1.25 μg/ml of cerulenin, both strains formed hyaline appressoria which did not penetrate onion epidermall walls. Appressorial melanization and epidermal penetrating capacity were restored in both strains by addition of the melanin precursor, 1,8-dihydroxynaphthalene (1,8-DHN) but were restored only in the wild type strain by addition of the precursor, scytalone.