TEMPORAL TRANSCRIPTIONAL PATTERN OF 3 MELANIN BIOSYNTHESIS GENES, PKS1, SCD1, AND THR1, IN APPRESSORIUM-DIFFERENTIATING AND NONDIFFERENTIATING CONIDIA OF COLLETOTRICHUM-LAGENARIUM

A phytopathogenic fungus, Colletotrichum lagenarium, produces melanize d appressoria that display temperature sensitive differentiation. Coni dia incubated in water at 24 degrees C germinated, and germ tubes diff erentiated into melanized appressoria. On the other hand, conidia incu bated in water at 32 degrees C germinated and produced germ tubes that elongated without appressorium differentiation. Conidia in 0.1% yeast extract solution at 32 degrees C germinated and developed into vegeta tive hyphae. In this study,we investigated the temporal transcriptiona l pattern of cloned melanin biosynthesis genes, PKS1, SCD1, and THR1, in these differentiating and nondifferentiating conidia. During appres sorium differentiation, de novo transcripts of the three melanin biosy nthesis genes accumulated 1 to 2 h after the start of conidial incubat ion at 24 degrees C, and the amount of transcripts began to decrease a t 6 h. In conidia germinating in water at 32 degrees C, the transcript ional pattern of the PKS1, SCD1, and THR1 genes was similar to that of these genes in appressorium-forming conidia, although no appressoria were formed. However, in conidia in 0.1% yeast extract solution at 32 degrees C, transcripts of the three melanin biosynthesis genes hardly accumulated.