The sodVI C gene from A. nidulans encodes a homologue of yeast, bovine and
human a-COP, which functions as part of the protein coat complex COPI  involved in vesicle production in the protein secretory pathway.
Phenotypic characterisation of the temperature sensitive sodVI C1 mutation showed that at 37°C a stable disomic for chromosome VI was produced. This was
confirmed genetically and the duplication of chromosome VI is proposed to act as a 'gene dosage' effect at the semi-restrictive temperature. Preliminary studies show that the sodVI C1 mutation may have an effect on secretion of certain classes of proteins from the hyphal tip.
Genetic characterisation of the sodVI C gene showed that the cloned gene was
indeed the bona fide sodVI C gene and not a multicopy suppressor of the
sodIV C1mutation. The sodVI C gene was also shown to be an essential gene and the sodVI C1 mutation identified as affecting the putative promoter region of the sodVI C gene. It is proposed that the socPCJ mutation in some way causes a down regulation of the transcription of the sodVI C gene, which is supported by the gene dosage effect seen at31°c.
The endomembrane system of A. nidulans was studied using GFP-tagged constructs. The endoplasmic reticulum of A. nidulans was studied in a mutant
background using an ER-localising GFP. It may be expected that the function of
COPI in the recycling of ER resident proteins from the Golgi to the ER is impaired by a mutation in the a-COP subunit, and therefore, would produce visible changes within ER morphology. However, this was not observed suggesting that the role of COPI within the secretory system is far more diverse, and the effect of the sodVI C1 mutation comes into play well before any visible changes in ER morphology occur. GFP-tagging of the sodVI C gene showed localisation to putative Golgi equivalents within A.nidulans.