Of the three Aspergilli with fully sequenced and publicly available genomes, A. fumigatus, A. nidulans, and A. oryzae, A. nidulans encodes the fewest enzymes commonly attributed to RNA silencing related processes. For example, A. nidulans is predicted to have only one ’Dicer', one Paz and Piwi domain (PPD) protein and two RNA dependent RNA polymerases (RDRPs), while the other two sequenced Aspergilli, and most other studied filamentous ascomycetes, are predicted to have at least two Dicers, two PPD proteins, and three RDRPs. The reduced number of these types of genes in A. nidulans suggests that it is an ideal model organism to study the biological function of these genes in filamentous fungi. In previous studies we have shown that the predicted A. nidulans PPD protein (RsdA) is required for RNA silencing during the vegetative cycle but that its two RDRPs (RrpA and RrpB) are not required for the same process. Interestingly, the simple experiments required to determine that the one predicted Dicer (DcrA) is required for RNA silencing in A. nidulans have not yet been completed because of an abnormal level of difficulty encountered during our attempts to obtain a dcrA deletion strain. In addition to our continual pursuit of a dcrA deletion strain, we are currently investigating two peculiar phenotypes associated with RNA silencing related genes but not thought to be directly related to RNA silencing during the vegetative cycle. These include a ’slow-growth' phenotype associated with dcrA over-expression and a ’selfing proficient' but ’crossing deficient' phenotype associated with rrpB deletion.
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)