Characterization of genes of the pheromone pathway of zygomycetes

We are interested to analyse the mycoparasitic interaction between Parasitella parasitica and the host Absidia glauca. One specific feature of this system concerns the mating type dependent infection of Absidia strains. Only plus Parasitella strains are able to infect minus Absidia strains or vice versa. One idea is, that the pheromone system of the parasite may be also used for recognition of hosts. Arguments for this thesis are, at first the host range of Parasitella. Only species of the order of Mucorales were infected. Second, the mating type dependent infection of Absidia. Third, the formation of a plasmatic fusion state between host and parasite, forming an active horiziontal gene transfer system.

The biosynthesis of pheromones seems to be similar in the group of Mucorales. Pheromones isolated from Blakeslea trispora (Choanephoraceae) induce very well zygophores (the first state of sexual development) in Mucor mucedo (Mucoraceae). The sexual hormone is trisporic acid, a derivative of beta-carotene. Both mating types form different precursors of this molecule. The precursors of one mating type can be converted to trisporic acid, only by the action of the complementary mating type. In a feedback system trisporic acid induces its own biosynthesis and also the biosynthesis of beta-carotene.

We are interested to isolate genes of this pathway to create knock-out mutants of the parasite. Analysis of infection behaviour of this mutants may be give hints about the relation between sexual and parasitic recognition.

One of this genes encodes for a dehydrogenase catalyzing the formation of methyltrisporate from 4-dihydromethyltrisporate, the plus specific precursor. The enzymatic activity is specific for the minus mating type. After purification of this enzyme from Mucor mucedo, the protein were digested with endoprotease lysC and several peptide sequences were determined. Sequence data were used for creation of a set of oligonucleotides for PCR. The cloned PCR fragment were used as probe for isolation of a cDNA clone and the complete genomic gene from Mucor mucedo. DNA sequence comparison show that the gene is member of the multigene family of the aldo/ ketoreductases. The gene is present in both mating types of Mucor mucedo. Now we analyse the expression pattern of the gene and isolate the homlogous genes from other zygomycetes.

Contact

Anke Burmester
Tel.: +49 (0)3641 949318
Fax: +49 (0)3641 949312
e-mail: b5buan@rz.uni-jena.de