In protozoan ciliates, the mechanism of self/non-self recognition is evolutionarily associated with the genetic mechanism of mating types. Within a species, these mating types may either be only two like sexes, or multiple, with the number limited to four, seven or eight, or virtually unlimited. The nearly 100 species of Euplotes, the most ubiquitous and cosmopolitan ciliate, all appear to include virtually unlimited numbers of mating types that cells express by synthesizing water-borne signaling proteins, known as pheromones. The knowledge of the structures of these pheromones and of their coding genes has for long been based only on studies of Euplotes species (i. e. E. raikovi, E. octocarinatus and E. nobilii) that branch into different central positions of the Euplotes phylogentic tree. More recently, we had the opportunity to analyze the pheromone and pheromone-gene structures in two Euplotes species, i.e. E. petzi and E. focardii, that lie at the opposed extremities of the tree: E. petzi (together with E. sinicus) represents the earliest branch of the tree, while E. focardii (together with the E. crassus/E. minuta/E. vannus species complex) represents the latest branch. In E. petzi, we found that the pheromone sequences extend for 32 amino acids and that the pheromone genes have extremely reduced dimensions (715 nucleotides, telomeres included), because they practically lack the regulatory 5’ region (only 72 nucleotides). In E. focardii, at the opposite, pheromone sequences extend for 85 amino acids and pheromone genes include a long regulatory 5’ region (1357 nucleotides) for an overall gene extension of 1951 nucleotides. Since the dimensions of the known pheromone and pheromone-gene sequences of E. raikovi, E. octocarinatus and E. nobilii are intermediary between those of their homologs in E. petzi and E. focardii, it appears that an earmark of Euplotes pheromone and pheromone gene evolution is a progressive increase of structural complexity, which presumes a parallel increase in complexity of the pheromone activities and of the regulatory mechanisms of pheromone gene expression.
The earlier the smaller: evidence from the study of the pheromone and pheromone-gene structures in the protozoan ciliate Euplotes
DI GIUSEPPE, GRAZIANO;DINI, FERNANDO;
2014-01-01
Abstract
In protozoan ciliates, the mechanism of self/non-self recognition is evolutionarily associated with the genetic mechanism of mating types. Within a species, these mating types may either be only two like sexes, or multiple, with the number limited to four, seven or eight, or virtually unlimited. The nearly 100 species of Euplotes, the most ubiquitous and cosmopolitan ciliate, all appear to include virtually unlimited numbers of mating types that cells express by synthesizing water-borne signaling proteins, known as pheromones. The knowledge of the structures of these pheromones and of their coding genes has for long been based only on studies of Euplotes species (i. e. E. raikovi, E. octocarinatus and E. nobilii) that branch into different central positions of the Euplotes phylogentic tree. More recently, we had the opportunity to analyze the pheromone and pheromone-gene structures in two Euplotes species, i.e. E. petzi and E. focardii, that lie at the opposed extremities of the tree: E. petzi (together with E. sinicus) represents the earliest branch of the tree, while E. focardii (together with the E. crassus/E. minuta/E. vannus species complex) represents the latest branch. In E. petzi, we found that the pheromone sequences extend for 32 amino acids and that the pheromone genes have extremely reduced dimensions (715 nucleotides, telomeres included), because they practically lack the regulatory 5’ region (only 72 nucleotides). In E. focardii, at the opposite, pheromone sequences extend for 85 amino acids and pheromone genes include a long regulatory 5’ region (1357 nucleotides) for an overall gene extension of 1951 nucleotides. Since the dimensions of the known pheromone and pheromone-gene sequences of E. raikovi, E. octocarinatus and E. nobilii are intermediary between those of their homologs in E. petzi and E. focardii, it appears that an earmark of Euplotes pheromone and pheromone gene evolution is a progressive increase of structural complexity, which presumes a parallel increase in complexity of the pheromone activities and of the regulatory mechanisms of pheromone gene expression.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
