Complementation of a stable Met2-1 mutant of the zygomycete Absidia glauca by the corresponding wild-type allele of the mycoparasite Parasitella parasitica, transferred during infection

Abstract

Compared with prokaryotes, where horizontal gene transfer events are frequently found and can be studied in the laboratory at the mechanistic level, few systems are known that allow direct experimental access to parasexual phenomena in eukaryotes. In zygomycetes, a basal lineage of fungi, several mycoparasitic fungi are known that inevitably form a cytoplasmic continuum with their hosts during infection. We provide evidence that, corresponding to the expectation suggested by the morphology of the infection process, gene transfer occurs from the parasite to the host. For analysing this parasexual system at the DNA level, we characterized interspecific recombinants obtained by infecting a stable methionine-auxotrophic Absidia glauca mutant with heavy rearrangements at the Met2-1 locus, which encodes homoserine acetyltransferase. Recipients were shown to be complemented by part of the corresponding gene from Parasitella parasitica. This foreign DNA is neither integrated at the putative Met2-2 locus in the recipient strain nor integrated at Met2-1, a locus encoding a hypothetical protein with amino acid similarity but with unknown function. Based on hybridization studies and on the phenotype of recipients that bear some mitotic instability of the acquired prototrophy, we propose that P. parasitica DNA is established in A. glauca recipients as extrachromosomally located replicons.

Complete Mitochondrial DNA Sequence of the Mucoralean Fungus Absidia glauca , a Model for Studying Host-Parasite Interactions

“…This biotrophic parasitism involves the fusion of specialized hyphal tips with the host A. glauca and other Mucor relatives ( 1 ). The transfer and expression of nuclear genes have been described for several genes involved in amino acid biosynthesis or that confer antibiotic resistance ( 2 , 3 ). After infection, auxotrophic mutants of A. glauca are complemented by their prototrophic counterparts of the parasite.…”

Complete Mitochondrial DNA Sequence of the Mucoralean Fusion Parasite Parasitella parasitica

“…Parasitism is thus necessarily linked with unidirectional transport of organelles from the parasite to the host. The transfer and expression of genes residing in nuclei have been verified for antibiotic resistance markers (2) and several genes involved in amino acid biosynthesis (2, 3). In order to initiate the analysis of mitochondrial information after transfer, we sequenced the mitochondrial DNA (mtDNA) of Parasitella parasitica .…”

Easy Access to a Cyclic Key Intermediate for the Synthesis of Trisporic Acids and Related Compounds

“…Furthermore several species of Mortierella (Mortierallale order) produce trisporoids that can induce sexual responses in Mucor mucedo and Phycomyces blakesleeanus [9]. Recently it has been demonstrated that the recognition between the parasite fungi Parasitella parasitica (Mocuraceae family) and the host Absidia glauca is mediated by trisporoids which are responsible for sexual phenomena [10,11]. Furthermore, evidence for the existence of genes of trisporoids synthesis in Glomus-like fungi (Phylum Glomeromycota) has been reported [12].…”