Sex chromosome conservation, DMRT1 phylogeny and gonad morphology in diploid Palearctic green toads (Bufo viridis subgroup).

Due to the prevailing sex chromosome homomorphy and large genome size, the knowledge on sex determination systems, sex chromosomes and sex-determining genes in amphibians remains scarce. Using 3 cross-amplifying sex-linked microsatellite markers, we uncover sex determination systems and sex chromosomes in purebred, diploid Palearctic green toads (Bufo viridis subgroup), which had so far only been characterized in laboratory-bred hybrids. Our data support an XY system in B. balearicus, B. viridis and B. variabilis. While females show recombination, it is strongly suppressed (or not detectable) in males. Markers corroborate the largest chromosome pair 1 (homologous to linkage group 1 of Xenopus tropicalis) to represent the sex chromosomes in diploid species of the B. viridis subgroup (B. siculus, B. shaartusiensis, B. balearicus, B. turanensis, B. variabilis, B. viridis, and probably B. boulengeri). This chromosome harbors DMRT1, a key gene of the sexual pathway in deeply divergent animal taxa. However, our phylogenetic analysis of a 600-bp fragment of that gene in diploid green toad taxa reveals that X and Y alleles cluster by species and not by gametolog. This suggests that XY-sequence similarity stems from occasional XY recombination within DMRT1, and we preliminarily reject its role as the master sex determination gene, pending future extension of this evidence to the entire DMRT1 gene. We further create a chain of evidence, which supports the hypothesis that linkage group 1 of X. tropicalis appears to be maintained as the largest chromosome (1), and thus is homologous in anuran karyotype evolution from pipid to hylid, bufonid and ranid anurans

Supplementary Material for: Sex Chromosome Conservation, <b><i>DMRT1</i></b> Phylogeny and Gonad Morphology in Diploid Palearctic Green Toads (<b><i>Bufo viridis </i></b>Subgroup)

Due to the prevailing sex chromosome homomorphy and large genome size, the knowledge on sex determination systems, sex chromosomes and sex-determining genes in amphibians remains scarce. Using 3 cross-amplifying sex-linked microsatellite markers, we uncover sex determination systems and sex chromosomes in purebred, diploid Palearctic green toads (<i>Bufo viridis</i> subgroup), which had so far only been characterized in laboratory-bred hybrids. Our data support an XY system in <i>B. balearicus</i>, <i>B. viridis</i> and <i>B. variabilis</i>. While females show recombination, it is strongly suppressed (or not detectable) in males. Markers corroborate the largest chromosome pair 1 (homologous to linkage group 1 of <i>Xenopus tropicalis</i>) to represent the sex chromosomes in diploid species of the <i>B. viridis</i> subgroup <i>(B. siculus, B. shaartusiensis, B. balearicus, B. turanensis, B. variabilis, B. viridis</i>, and probably <i>B. boulengeri)</i>. This chromosome harbors <i>DMRT1</i>, a key gene of the sexual pathway in deeply divergent animal taxa. However, our phylogenetic analysis of a 600-bp fragment of that gene in diploid green toad taxa reveals that X and Y alleles cluster by species and not by gametolog. This suggests that XY-sequence similarity stems from occasional XY recombination within <i>DMRT1</i>, and we preliminarily reject its role as the master sex determination gene, pending future extension of this evidence to the entire <i>DMRT1 </i>gene. We further create a chain of evidence, which supports the hypothesis that linkage group 1 of <i>X. tropicalis</i> appears to be maintained as the largest chromosome (1), and thus is homologous in anuran karyotype evolution from pipid to hylid, bufonid and ranid anurans

Host-specific assemblages typify gut microbial communities of related insect species

Zakee L Sabree12* and Nancy A Moran13 Author Affiliations 1 Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA 2 Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA 3 Section of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USAMutualisms between microbes and insects are ubiquitous and facilitate exploitation of various trophic niches by host insects. Dictyopterans (mantids, cockroaches and termites) exhibit trophisms that range from omnivory to strict wood-feeding and maintain beneficial symbioses with the obligate endosymbiont, Blattabacterium, and/or diverse gut microbiomes that include cellulolytic and diazotrophic microbes. While Blattabacterium in omnivorous Periplaneta is fully capable of provisioning essential amino acids, in wood-feeding dictyopterans it has lost many genes for their biosynthesis (Mastotermes and Cryptocercus) or is completely absent (Heterotermes). The conspicuous functional degradation and absence of Blattabacterium in most strict wood-feeding dictyopteran insects suggest that alternative means of acquiring nutrients limited in their diet are being employed. A 16S rRNA gene amplicon resequencing approach was used to deeply sample the composition and diversity of gut communities in related dictyopteran insects to explore the possibility of shifts in symbiont allegiances during termite and cockroach evolution. The gut microbiome of Periplaneta, which has a fully functional Blattabacterium, exhibited the greatest within-sample operational taxonomic unit (OTU) diversity and abundance variability than those of Mastotermes and Cryptocercus, whose Blattabacterium have shrunken genomes and reduced nutrient provisioning capabilities. Heterotermes lacks Blattabacterium and a single OTU that was 95% identical to a Bacteroidia-assigned diazotrophic endosymbiont of an anaerobic cellulolytic protist termite gut inhabitant samples consistently dominates its gut microbiome. Many host-specific OTUs were identified in all host genera, some of which had not been previously detected, indicating that deep sampling by pyrotag sequencing has revealed new taxa that remain to be functionally characterized. Further analysis is required to uncover how consistently detected taxa in the cockroach and termite gut microbiomes, as well as the total community, contribute to host diet choice and impact the fate of Blattabacterium in dictyopterans.Integrative [email protected]