Conidia are common asexual spores for fungal reproduction. A number of studies have elucidated the regulation of conidiation in two model ascomycetes, Aspergillus nidulans and Neurospora crassa. These organisms are evolutionarily distant and their conidiation is morphologically distinct. To understand the evolutionary origins of asexual sporulation, it is critical to examine the conserved function of conidiation regulatory genes between these two species. We concentrated our interests on seven major genes fluG, flbC, flbD, abaA, wetA, medA, and stuA that are known as conidiation regulators in A. nidulans. Disruption of the genes resulted in conidiation defects in A. nidulans, but the degree of the defects in conidia production and conidiophore formation varies. By analysis of sequences of the A. nidulans conidiation genes, we identified seven orthologs in N. crassa. Disruption of flbC, medA, and stuA orthologs leads to macro-conidiation defects, whereas fluG, flbD, abaA, and wetA orthologs are not associated with macro-conidiation in N. crassa. Expression of N. crassa fluG, flbD, wetA, medA, and stuA orthologs complemented the conidiation defect for the corresponding A. nidulans mutant. This implies that the biochemical functions of these genes are conserved between the two species. In contrast, expression of N. crassa flbC and abaA did not complement conidiation defects in the corresponding A. nidulans mutants. Our data supports the independent evolution in the ascomycetes of conidiation regulatory networks, potentially from a common toolkit.
Full conference title:
26th Fungal Genetics Conference
- Fungal Genetics Conference 26th (2005)