In a mutagenic screening designed to obtain mutations altered in the nuclear transport of PacC we serendipitously isolated a conditional mutation leading to an accumulation of nuclei. The mutation mapped at a gene denoted as pprA because it encodes for a protein with several pentatricopeptide repeats (PPR). PPR proteins are abundant in plants and they play different functions; however, all of them appeared to be in a close relationship with mitochondria and chloroplasts. In A. nidulans, pprA is an essential gene and it is the first pentatricopeptide protein that has been characterized. The thermosensitive mutation, pprA1, causes a strong growth defect. Mutant hyphae are much shorter and thicker than those of the wild-type strain. At the restrictive temperature nuclei accumulate and have not apparent organisation. Consistent with this the mitotic spindles are formed in anomalous orientations. The actin cytoskeleton is also affected. The actin accumulation at the cell tip is less abundant, although still prominent, and actin cables are not observed. In Aspergillus and budding yeast, mitochondria interact with the actin cytoskeleton and use it to move throughout the cell. As expected from the actin cytoskeleton disturbance, caused by the pprA1 mutation, mitochondria appeared completely fragmented. We propose two different ways in which this essential protein could carry out its role. PprA could be acting either through the mitochondria integrity or directly, in the organisation of both cytoskeletons, which are required for hyphal growth and nuclear distribution maintenance.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)