THE ALTERNARIA-ALTERNATA MELANIN BIOSYNTHESIS GENE RESTORES APPRESSORIAL MELANIZATION AND PENETRATION OF CELLULOSE MEMBRANES IN THE MELANIN-DEFICIENT ALBINO MUTANT OF COLLETOTRICHUM-LAGENARIUM
Y. Takano et al., THE ALTERNARIA-ALTERNATA MELANIN BIOSYNTHESIS GENE RESTORES APPRESSORIAL MELANIZATION AND PENETRATION OF CELLULOSE MEMBRANES IN THE MELANIN-DEFICIENT ALBINO MUTANT OF COLLETOTRICHUM-LAGENARIUM, Fungal genetics and biology, 21(1), 1997, pp. 131-140
Colletotrichum lagenarium and Alternaria alternata produce a dark pigm
ent, melanin, The C. lagenarium PKS1 and A. alternata ALM genes are in
volved in polyketide synthesis in the melanin biosynthesis pathway, PK
S1 encodes a type I polyketide synthase, For functional comparison of
the ALM gene with the PKS1 gene, we examined whether the A. alternata
ALM gene could restore melanin synthesis in C. lagenarium albino mutan
t (Pks1(-)). The ALM gene transformed the albino mutant (Pks1(-))to me
lanin-producing phenotypes, designated CAL transformants. The pigment
intensity of both melanized colonies and appressoria of CAL transforma
nts was weaker than that of the wild type, Ultrastructural studies of
the cell walls of appressoria demonstrated that CAL transformants form
ed an outer melanized layer, as did the wild type. On the other hand,
the thin inner and middle layers were less electron-dense than those o
f the wild type, CAL transformants were able to penetrate cellulose me
mbranes as effectively as the wild type. By contrast, the penetration
frequency of CAL transformants on cucumber cotyledons was remarkably r
educed compared to that of the wild type. During conidial germination,
the PKS1 transcript accumulated de novo in both the wild-type and CAL
transformants after the start of conidial incubation, On the other ha
nd, ALM transcript accumulated in conidia of CAL transformants before
the start of conidial incubation. (C) 1997 Academic Press.