THE PHEROMONES AND PHEROMONE GENES OF NEW STOCKS OF THE EUPLOTES-OCTOCARINATUS SPECIES COMPLEX

Two new stocks of the hypotrichous ciliate Euplotes octocarinatus isol ated in Florida and Maryland/USA were identified as members of mating type VI (mt(2)mt(3)), secreting pheromones 2 and 3 and mating type VII (mt(1)mt(1)), secreting pheromone 1. These are two out of the ten alr eady known mating types of Euplotes octocarinatus. Results of breeding experiments suggest that the new stocks belong to new syngens of this species complex. The analysis of the macronuclear molecules containin g the new pheromone 1, 2 and 3-encoding genes show that their structur e is very similar to those isolated before. Like in these genes the co ding regions are interrupted by three introns with a high degree of ho mology. A comparison of the deduced amino acid sequences of the new ph eromones with the known versions of the corresponding pheromones revea ls homologies of 76 to 93% for the secreted proteins whereas the leade r sequences are 98 to 100% identical. In both versions of pheromones 1 , 2 and 3 there are ten cysteine residues which are located at strictl y conserved positions. In spite of their differences both versions of pheromones 1, 2 and 3 show the same specific biological activity. This might be an indication that the unchanged residues participate in rec eptor binding.