1,721,063 research outputs found
Variabilità elettroforetica nel gruppo di specie marine Euplotes crassus-minuta-vannus (CILIOPHORA, HYPOTRICHIDA).
No full textThe pheromone genes of the self/non-self recognition mechanism of the ciliate Euplotes crassus generate multiple transcripts by an alternative splicing of ‘matryoshka’ introns
No full textIn ciliates, cell-type distinctive protein pheromones control a self/non-self recognition mechanism responsible for the cell switching between the vegetative and sexual stages of the life cycle. These signaling molecules are encoded by genes (pheromone genes) that in the cell somatic nucleus (macronucleus) represent the transcriptionally active versions of transcriptionally silent genes allelic at the same genetic locus mat of the cell germinal nucleus (micronucleus). In the course of evolution, in Euplotes, the native single multiallelic mat locus underwent duplication among species which, such as E. crassus, form the latest branching clade of the phylogenetic tree. Because of this duplication, E. crassus expresses two distinct families of pheromone genes instead of a single family, as is the case in species of earlier branching clades.
We analyzed the structure and expression of a number of E. crassus pheromone genes representative of the two families. Like their orthologs of other Euplotes species, these genes show 5’-leader regions that are much more extended than the coding regions, lack canonical regulatory sequences for gene transcription, and synthesize multiple transcripts (in addition to the pheromone-specific one) through the activity of two distinct transcription start sites and a mechanism of alternative intron splicing. These E. crassus introns have been found to be unique with respect to introns of all the other Euplotes pheromone genes. They can be distinguished between ‘matryoshka’ introns, residing one inside the other like Russian Dolls, and ‘non-matryoshka’ introns. While the former possess canonical GTA/TAG splicing sites, the latter possess CTA/TAC splicing sites complementary to the canonical GTA/TAG splicing sites. This strongly suggests that both the DNA strands of the E. crassus pheromone genes can be used as template for transcription. We are currently attempting to verify this hypothesis and assign a function to the products of the multiple E. crassus pheromone gene transcripts
The often overlooked coming out of ciliates: biological and experimental benefits from accepting genetically identical conspecifics as sexual partners
No full textCiliates usually manifest sex in the form of conjugation, a unique phenomenon in which cells temporarily unite two by two in mating pairs to perform a mutual exchange of gamete-nuclei derived from meiotic products of their germinal micronucleus. The native view of conjugation as a spontaneous manifestation associated with environmental famine conditions was eventually denied by the milestone Sonneborn’s finding (PNAS, 1937) that the most popular ciliate, Paramecium, actually controls conjugation through a genetic mechanism of mating types. Being only two in the Paramecium species studied by Sonneborn, these mating types were functionally equated to ‘male’ and ‘female’ sexes. And, as a consequence of this equation, conjugation was since thought of as a phenomenon committed to involve, as a rule, genetically distinct cells representing two ‘complementary’ mating types. However, this is a wrong tenet adverse the evidence that many ciliates conjugate with no discrimination between sex identity and diversity. And from this no discrimination both the ciliate biology and the students of ciliate biology draw benefit. The ciliate biology, because the homo-sexual pairs (yet ineffective to reshuffle the species gene pool) multiply the opportunity for cells to practice conjugation which, in every case, determines the initiation of a new life cycle and the replacement of the cell ‘old’ transcriptionally active somatic (macronuclear) genome with a completely new one generated from the permanently ‘young’ transcriptionally inert germinal (micronuclear) genome. The students of ciliate biology, because homo-sexual pairs form without requiring physical interactions between sexually/genetically different cells. They form as well in cultures of cells of the same identity previously suspended with filtrates from cultures of conspecific cells of different identity. Which immediately identifies species that interact sexually via water-borne mating signals (pheromones), and greatly facilitates the isolation and function-structure characterization of these signals directly from cell-culture filtrates
Competizione tra diversi feromoni di Euplotes raikovi nell'interazione con uno stesso recettore. Atti del 55° Congresso Nazionale U.Z.I.
No full textNot too big for its mouth: direct evidence of a macrodasyidan gastrotrich preyed in nature by a dileptid ciliate
Full text linkNearly ubiquitous and usually speciose in most aquatic habitats, the meiofaunal-sized gastrotrichs are recognized as an important component of marine and freshwater ecosystems. The common observations that gastrotrichs feed on bacteria, microalgae and biodetritus strongly imply that they play a relevant role in linking the microbial loop to the higher trophic levels. Which are the organisms that in turn prey on gastrotrichs is, however, a substantially unexplored question. Inspecting meiofauna samples collected from shallow sites of the Tyrrhenian coast, we had the chance to spot a wild case of a macrodasyidan gastrotrich predated by a dileptid ciliate. This case is documented here with a set of in-vivo photos, jointly with an unequivocal taxonomic identification of the preyed gastrotrich with Paraturbanella teissieri and a tentative identification of the predator ciliate with Pseudomonilicaryon marinus
Identification and initial characterization of the pheromone receptor of type-II cells of Euplotes raikovi. J. Protozool.
No full textOssidazione dei feromoni e invecchiamento cellulare in Euplotes raikovi. Atti del 59° Congresso Nazionale U.Z.I.
No full textIsolamento riproduttivo e variabilità elettroforetica nel gruppo di specie Euplotes crassus-minuta-vannus.
No full textElectrophoretic variations within the group of species Euplotes crassus, E. minuta and E. vannus.
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