Certain highly-efficient gene conversion events have been shown to be dependent on a new class of "mobility endonucleases". Representing a minimum of three types of DNA-cleavage proteins based on their cleavage patterns and amino acid sequences, these endonucleases are found in association with group I introns, promoting conversion of intron-minus alleles to intron-plus. Sequence analysis of the mitochondrial genome of the filamentous fungus Podospora anserina predicts an unprecedented number of such endonucleases (10-30), providing an opportunity to 1) address the frequency of mobility endonucleases within the mitochondria of Podospora, 2) characterize selected endonucleases in regard to their substrate requirements and specificity and 3) study the expression and regulation of these proteins and their function in the mitochondria. The Podospora system additionally provides unique opportunities to study the potential involvement of mobility endonucleases in the phenomena of mitochondrially-related senescence and horizontal gene transfer. %%% The objective of this proposal is to 1) characterize and compare a selected endonucleases candidate gene in Podospora with a highly similar candidate in Neurospora, utilizing a variety of molecular and genetic techniques and assays, 2) expand this system to study other putative endonucleases, and 3) develop methods to evaluate their role in sentence, the Podospora life cycle and horizontal gene transfer.
