Conspecific male animals fight for resources such as food and mating opportunities but typically stop fighting after assessing their relative fighting abilities to avoid serious injuries. Physiologically, how the fighting behavior is controlled remains unknown. Using the fighting fish Betta splendens, we studied behavioral and brain-transcriptomic changes during the fight between the two opponents. At the behavioral level, surface-breathing, and biting/striking occurred only during intervals between mouth-locking. Eventually, the behaviors of the two opponents became synchronized, with each pair showing a unique behavioral pattern. At the physiological level, we examined the expression patterns of 23,306 brain transcripts using RNA-sequencing data from brains of fighting pairs after a 20-min (D20) and a 60-min (D60) fight. The two opponents in each D60 fighting pair showed a strong gene expression correlation, whereas those in D20 fighting pairs showed a weak correlation. Moreover, each fighting pair in the D60 group showed pair-specific gene expression patterns in a grade of membership analysis (GoM) and were grouped as a pair in the heatmap clustering. The observed pair-specific individualization in brain-transcriptomic synchronization (PIBS) suggested that this synchronization provides a physiological basis for the behavioral synchronization. An analysis using the synchronized genes in fighting pairs of the D60 group found genes enriched for ion transport, synaptic function, and learning and memory. Brain-transcriptomic synchronization could be a general phenomenon and may provide a new cornerstone with which to investigate coordinating and sustaining social interactions between two interacting partners of vertebrates.

As an ancient seed plant, cycads are one of the few gymnosperms that develop a root symbiosis with cyanobacteria, which has allowed cycads to cope with harsh geologic and climatic conditions during the evolutionary process. However, the endophytic microbes in cycad roots remain poorly identified. In this study, using next-generation sequencing techniques, we investigated the microbial diversity and composition of both the coralloid and regular roots of Cycas bifida (Dyer) K.D. Hill. Highly diverse endophytic communities were observed in both the coralloid and regular roots. Of the associated bacteria, the top five families were the Nostocaceae, Sinobacteraceae, Bradyrhizobiaceae, Bacillaceae, and Hyphomicrobiaceae. The Nectriaceae, Trichocomaceae, and Incertae sedis were the predominant fungal families in all root samples. A significant difference in the endophytic bacterial community was detected between coralloid roots and regular roots, but no difference was observed between the fungal communities in the two root types. Cyanobacteria were more dominant in coralloid roots than in regular roots. The divergence of cycad root structures and the modified physiological processes may have contributed to the abundance of cyanobionts in coralloid roots. Consequently, the colonization of cyanobacteria inhibits the assemblage of other endophytes. Our results contribute to an understanding of the species diversity and composition of the cycad-endophyte microbiome and provide an abbreviated list of potential ecological roles of the core microbes present.

BackgroundComparative genomics provides insights into the diversification of bacterial species. Bacterial speciation usually takes place with lasting homologous recombination, which not only acts as a cohering force between diverging lineages but brings advantageous alleles favored by natural selection, and results in ecologically distinct species, e.g., frequent host shift in Xanthomonas pathogenic to various plants.ResultsUsing whole-genome sequences, we examined the genetic divergence in Xanthomonas campestris that infected Brassicaceae, and X. citri, pathogenic to a wider host range. Genetic differentiation between two incipient races of X. citri pv. mangiferaeindicae was attributable to a DNA fragment introduced by phages. In contrast to most portions of the genome that had nearly equivalent levels of genetic divergence between subspecies as a result of the accumulation of point mutations, 10% of the core genome involving with homologous recombination contributed to the diversification in Xanthomonas, as revealed by the correlation between homologous recombination and genomic divergence. Interestingly, 179 genes were under positive selection; 98 (54.7%) of these genes were involved in homologous recombination, indicating that foreign genetic fragments may have caused the adaptive diversification, especially in lineages with nutritional transitions. Homologous recombination may have provided genetic materials for the natural selection, and host shifts likely triggered ecological adaptation in Xanthomonas. To a certain extent, we observed positive selection nevertheless contributed to ecological divergence beyond host shifting.ConclusionAltogether, mediated with lasting gene flow, species formation in Xanthomonas was likely governed by natural selection that played a key role in helping the deviating populations to explore novel niches (hosts) or respond to environmental cues, subsequently triggering species diversification.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1369-8) contains supplementary material, which is available to authorized users.

Gene flow between species may last a long time in plants. Reticulation inevitably causes difficulties in phylogenetic reconstruction. In this study, we looked into the genetic divergence and phylogeny of 20 Lilium species based on multilocus analyses of 8 genes of chloroplast DNA (cpDNA), the internally transcribed nuclear ribosomal DNA (nrITS) spacer and 20 loci extracted from the expressed sequence tag (EST) libraries of L. longiflorum Thunb. and L. formosanum Wallace. The phylogeny based on the combined data of the maternally inherited cpDNA and nrITS was largely consistent with the taxonomy of Lilium sections. This phylogeny was deemed the hypothetical species tree and uncovered three groups, i.e., Cluster A consisting of 4 taxa from the sections Pseudolirium and Liriotypus, Cluster B consisting of the 4 taxa from the sections Leucolirion, Archelirion and Daurolirion, and Cluster C comprising 10 taxa mostly from the sections Martagon and Sinomartagon. In contrast, systematic inconsistency occurred across the EST loci, with up to 19 genes (95%) displaying tree topologies deviating from the hypothetical species tree. The phylogenetic incongruence was likely attributable to the frequent genetic exchanges between species/sections, as indicated by the high levels of genetic recombination and the IMa analyses with the EST loci. Nevertheless, multilocus analysis could provide complementary information among the loci on the species split and the extent of gene flow between the species. In conclusion, this study not only detected frequent gene flow among Lilium sections that resulted in phylogenetic incongruence but also reconstructed a hypothetical species tree that gave insights into the nature of the complex relationships among Lilium species.

The principal event underlying the development of prion disease is the conversion of soluble cellular prion protein (PrPC) into its disease-causing isoform, PrPSc. This conversion is associated with a marked change in secondary structure from predominantly α-helical to a high β-sheet content, ultimately leading to the formation of aggregates consisting of ordered fibrillar assemblies referred to as amyloid. In vitro, recombinant prion proteins and short prion peptides from various species have been shown to form amyloid under various conditions and it has been proposed that, theoretically, any protein and peptide could form amyloid under appropriate conditions. To identify the peptide segment involved in the amyloid core formed from recombinant full-length mouse prion protein mPrP(23–230), we carried out seed-induced amyloid formation from recombinant prion protein in the presence of seeds generated from the short prion peptides mPrP(107–143), mPrP(107–126), and mPrP(127–143). Our results showed that the amyloid fibrils formed from mPrP(107–143) and mPrP(127–143), but not those formed from mPrP(107–126), were able to seed the amyloidogenesis of mPrP(23–230), showing that the segment residing in sequence 127–143 was used to form the amyloid core in the fibrillization of mPrP(23–230).