Ciliate pheromone structures and activity: a review

Abstract

As in animals and other multicellular organisms, protozoan ciliates communicate via diffusible signalling pheromones. These pheromones have been identified in the culture supernatant of various species. However, their isolation and definitive structural characterization have been achieved only in species of Blepharisma and Euplotes. With the exception of the two B. japonicum pheromones represented by a tryptophan-related molecule and a glycoprotein, all the other pheromones isolated from Euplotes species are proteins that vary in extension between 38 and 109 amino acids. They form species-specific families of structurally homologous members, in full accord with their multi-allelic determination at an apparently single genetic locus. The determination of the Nuclear Magnetic Resonance (NMR) solution structures of E. raikovi and E. nobilii pheromones has provided direct evidence that, although structurally unique, Euplotes pheromones adopt a common, speciesspecific three-helix folding. This close structural homology among members of the same family well accounts for the pheromone capacity to compete with one another in cell receptor binding reactions and elicit context-dependent, autocrine (growth-promoting) or paracrine (mating-inducing) cell responses.

Ciliates in Planktonic Food Webs: Communication and Adaptive Response

“…Irrespective of minor specific differences, there is no reason to assume that the basic principles of information exchange during conjugation deciphered with Tetrahymena, Euplotes, Blepharisma and a few other model species (Dini and Nyberg 1993;Hausmann et al 1996;Luporini et al 2015;Nanney 1980) in the laboratory do not apply to natural populations.…”

“…The most obvious example of ciliate-ciliate communication originates from sexual recombination. Since Sonneborn's seminal studies with Paramecium (Sonneborn 1936(Sonneborn , 1937, mating in ciliates has been extensively studied (reviewed by Dini and Nyberg 1993;Luporini et al 2015; see Chapter 'Pheromone Signalling' by Luporini). In outbreeding ciliates, sexual recombination can be identified relatively easily by observing conjugating specimens (Fig.…”

“…The pheromone peptides and proteins belong to one of the three classes of secondary metabolites synthesised by ciliates (reviewed by Guella et al 2010;Luporini et al 2015; see Chapter 'Pheromone Signalling' by Luporini). The second class of products comprises compounds of mixed biosynthetic origin broadly defined as pigments.…”

Predator-Prey Interactions in Ciliated Protists

“…Whittaker [2] originally defined protists as those "organisms which are unicellular or unicellular-colonial and which form no tissues," and for this reason they must carry out at the cellular level all the basic functions which can be observed in multicellular eukaryotes. Among these functions, self-nonself recognition mechanisms are represented by a large repertoire in protists and can trigger either autocrine or paracrine processes in some ciliates (see [3] for a review), together with the capability to detect prey (food) or predators in others. In this regard, it is known that protists have developed a variety of strategies of feeding behaviors especially in response to different environmental factors, together with a diverse kind of food available in micro-habitats.…”

Gamete signalling underlies the evolution of mating types and their number

“…The number of mating types in the genus Euplotes varies from five to 12 [ 87 ]. Many species, including E. octocarinatus , E. raikovi , E. patella and E. woodru , secrete mating-type-specific substances [ 87 , 88 ]. Individual cells grow vegetatively when binding to their own pheromone secreted continuously in the extracellular environment.…”