Project description:Ixodes pacificus, the vector of Borrelia burgdorferi (Bb) on the west coast, feeds on a variety of hosts including rodents, birds, and lizards. While rodents are reservoirs for Bb and can infect juvenile ticks, lizards are Bb-refractory. Despite the range of bloodmeals for I. pacificus, it is undetermined how larval host bloodmeal identity may affect future nymphal vector competence. Here, we conducted a transcriptome analysis on I. pacificus to determine whether and through what mechanisms host bloodmeal history affects vector competency of I. pacificus for the Lyme disease pathogen.
Project description:Understanding the conditions that promote the evolution of reproductive isolation, and thus speciation. Here we empirically test some of the key predictions of speciation theory (Coyne 2004; Kohn 2005) by experimentally evolving the initial stages of speciation in yeast. After allowing replicate populations to adapt to two divergent environments, we observed the consistent, de novo evolution of two forms of postzygotic isolation: reduced rate of mitotic reproduction and reduced efficiency of meiotic reproduction. In general, divergent selection resulted in greater reproductive isolation than parallel selection, as predicted by ecological speciation theory. Our experimental system allowed for the first controlled comparison of the relative importance of ecological and genetic mechanisms of isolation, and the novel ability to quantify the effects of antagonistic epistasis. For mitotic reproduction, hybrid inferiority was conditional upon the selective environments and was both ecological and genetic in basis. In contrast, isolation associated with meiotic reproduction was unconditional and was caused solely by genetic mechanisms. Overall, our results show that adaption to divergent environments promotes the evolution of isolation through antagonistic epistasis, providing evidence of a plausible common avenue to speciation and adaptive radiation in nature (Schluter 2000,2001: Funk 2006) Keywords: Speciation, antagonistic epistasis, divergent adaptation
Project description:Lizards cannot naturally regenerate limbs but are the closest known relatives of mammals capable of epimorphic tail regrowth. However, the mechanisms regulating lizard blastema derivation and chondrogenesis remain unclear. We utilized single-cell RNA sequencing analyses of regenerating lizard tails throughout the course of regeneration to assess diversity and heterogeneity in regeneating tail cell populations.
Project description:Background: The Dobzhansky-Muller (D-M) model of speciation by genic incompatibility is widely accepted as the primary cause of interspecific postzygotic isolation. Since the introduction of this model, there have been theoretical and experimental data supporting the existence of such incompatibilities. However, speciation genes have been largely elusive, with only a handful of candidate genes identified in a few organisms. The Saccharomyces sensu stricto yeasts have small genomes, can be easily cultured, and can mate interspecifically to produce sterile hybrids, are thus an ideal model for studying postzygotic isolation. Among them, only a single D-M pair has been found, between S. bayanus and S. cerevisiae, comprising the mitochondrially targeted product of a nuclear gene, AEP2, and a mitochondrially encoded locus, OLI1, the 5' region of whose transcript is bound by Aep2. Thus far, no D-M pair of nuclear genes has been identified between any sensu stricto yeasts. Methods: We report here the first detailed genome-wide analysis of rare F2 progeny from an otherwise sterile hybrid, and show that no classic D-M pairs of speciation genes exist between the nuclear genomes of the closely related yeasts S. cerevisiae and S. paradoxus. Instead, our analyses suggest that more complex interactions may be responsible for their post-zygotic separation. These interactions most likely involve multiple loci having weak effects, as there were multiple significant pairwise combinations of loci, with no single combination being completely excluded from the viable F2s. Conclusions: The lack of a nuclear encoded classic D-M pair between these two yeasts, yet the existence of multiple loci that may each exert a small effect through complex interactions, suggests that initial speciation events might not always be mediated by D-M pairs. An alternative explanation may be that "death by a thousand cuts" leads to speciation, whereby an accumulation of polymorphisms can lead to an incompatibility between the species "transcriptional and metabolic networks, with no single pair at least initially being responsible for the incompatibility. After such a speciation event, it is possible that one or more D-M pairs might subsequently arise following isolation. Genotypes for hybrids between S. cerevisiae and S. paradoxus. A genotyping experiment design type classifies an individual or group of individuals on the basis of alleles, haplotypes, SNP's.
Project description:Male offspring resulting from interbreeding of genetically diverged populations are frequently infertile or subfertile due to failures in chromosome pairing. The resulting reproductive isolation of the two populations represents an early step in speciation. In inter-subspecific mouse hybrids, the binding of the histone methyltransferase PRDM9 to both chromosome homologues at matching positions is important for successful chromosome pairing. This mechanistic property underpins Prdm9’s role as an important speciation gene, the only one yet identified in vertebrates. Here we show that this behaviour holds true for more distant evolutionary relationships across the species barrier. By altering PRDM9’s binding pattern, we restore fertility in hybrids of distinct species.
Project description:Insulators are considered as chromosome organizers. BEAF, one of the insulator proteins, is highly conserved in Drosophila speies but also limited to Drosophila spcies. BEAF associates with TSS of active genes. Comparative study of BEAF binding landscapes in four Drosophila species reveals BEAF association with gene pairs, and the results suggest the role of gain or loss of BEAF binding during the speciation of Drosophila species. DNA sample from ChIP for BEAF and input are collected for each of four Drosophila species