To investigate the effects of cell wall on the pigmentation and branching in Aspergillus nidulans, the ultrastructure and cytochemical composition of cell wall in wild type (FGSC4) and npgAI mutant (no pigmentation through the whole life cycle, WX17) were examined. Scanning electron microscope (SEM) showed that the hyphal surface and branching in WX17 were rough and poorly formed, in contrast to those in FGSC4 showing smooth and well developing, respectively. Transmission electron microscope (TEM) and carbohydrate staining showed that the hyphal wall of FGSC4 layered as H 1, H2, H3, and H4 were mainly composed of protein, chitin, B-glucan, and the complex of chitin and B-glucan respectively. However the hyphal wall of WX17 was lacking HI and H3 layers suggesting that the defect in pigmentation and hyphal branching of npgAI mutant might be due to the lack of the B-glucan layer in the cell wall. To study the function of the gene npgA in constructing cell wall structure, we isolated DNA fragment that was able to complement npgA 1 mutation from the genomic library of FGSC4. From its nucleotide sequence, we found that there was an open reading frame (ORF) in which the amino acid sequence was homologous to that of SLC1 gene which encoded fatty acyltransferase in Saccharomyces cerevisiae. The fragment was also capable of complementing the defect in a 1-acyl-sn-glycerol-3-phosphate-acyltransferase, encoded by the gene plsC, of Escherichia coli. From these results, it could be concluded that the npgA l -complementing element might play a role in constructing cell wall structure or depositing pigment.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)