Social dominance alters nutrition-related gene expression immediately: transcriptomic evidence from a monomorphic queenless ant.

Queen-worker differentiation in eusocial organisms may have originated from decoupling of maternal care and reproductive behaviours. Recent advances in sequencing techniques have begun to elucidate the molecular basis of queen-worker differentiation. However, current knowledge of the molecular basis of caste differentiation is limited, especially to species with morphological castes. It seems likely that at the dawn of eusociality morphologically undifferentiated, monomorphic females underwent physiological differentiation that yielded egg-laying and caretaking castes. The molecular basis of such physiological differentiation may provide evolutionary insight into the emergent state of eusociality. In this study, we identify genes associated with monomorphic caste differentiation, specifically focusing on the onset of queen-worker differentiation, using a monomorphic queenless ant, Diacamma sp., that secondarily lost morphological castes. Using individuals experimentally manipulated to become sterile or reproductive, we identified 1546 caste-biased transcripts in brain and 10 in gaster. Because caste differentiation occurs in Diacamma soon after eclosion via behavioural dominance, identified transcripts are interpreted as molecular agents responding immediately to dominance rank formation. Among identified genes, expression levels of genes involved in nutrition processing and storage, such as insulin signalling genes and hexamerins, were strongly altered soon after dominance rank formation. We conclude that the rapid modification of nutrition-related genes in response to social rank may be the fundamental mechanism underlying caste differentiation in Diacamma. Together with functional evidence from the literature, we show that a specific set of genes frequently plays a role in reproductive differentiation across systems with and without morphological castes.

Comparative transcriptomics reveals the conserved building blocks involved in parallel evolution of diverse phenotypic traits in ants.

BACKGROUND: Reproductive division of labor in eusocial insects is a striking example of a shared genetic background giving rise to alternative phenotypes, namely queen and worker castes. Queen and worker phenotypes play major roles in the evolution of eusocial insects. Their behavior, morphology and physiology underpin many ecologically relevant colony-level traits, which evolved in parallel in multiple species. RESULTS: Using queen and worker transcriptomic data from 16 ant species we tested the hypothesis that conserved sets of genes are involved in ant reproductive division of labor. We further hypothesized that such sets of genes should also be involved in the parallel evolution of other key traits. We applied weighted gene co-expression network analysis, which clusters co-expressed genes into modules, whose expression levels can be summarized by their 'eigengenes'. Eigengenes of most modules were correlated with phenotypic differentiation between queens and workers. Furthermore, eigengenes of some modules were correlated with repeated evolution of key phenotypes such as complete worker sterility, the number of queens per colony, and even invasiveness. Finally, connectivity and expression levels of genes within the co-expressed network were strongly associated with the strength of selection. Although caste-associated sets of genes evolve faster than non-caste-associated, we found no evidence for queen- or worker-associated co-expressed genes evolving faster than one another. CONCLUSIONS: These results identify conserved functionally important genomic units that likely serve as building blocks of phenotypic innovation, and allow the remarkable breadth of parallel evolution seen in ants, and possibly other eusocial insects as well.

Caste-Specific and Sex-Specific Expression of Chemoreceptor Genes in a Termite.

The sophisticated colony organization of eusocial insects is primarily maintained through the utilization of pheromones. The regulation of these complex social interactions requires intricate chemoreception systems. The recent publication of the genome of Zootermopsis nevadensis opened a new avenue to study molecular basis of termite caste systems. Although there has been a growing interest in the termite chemoreception system that regulates their sophisticated caste system, the relationship between division of labor and expression of chemoreceptor genes remains to be explored. Using high-throughput mRNA sequencing (RNA-seq), we found several chemoreceptors that are differentially expressed among castes and between sexes in a subterranean termite Reticulitermes speratus. In total, 53 chemoreception-related genes were annotated, including 22 odorant receptors, 7 gustatory receptors, 12 ionotropic receptors, 9 odorant-binding proteins, and 3 chemosensory proteins. Most of the chemoreception-related genes had caste-related and sex-related expression patterns; in particular, some chemoreception genes showed king-biased or queen-biased expression patterns. Moreover, more than half of the genes showed significant age-dependent differences in their expression in female and/or male reproductives. These results reveal a strong relationship between the evolution of the division of labor and the regulation of chemoreceptor gene expression, thereby demonstrating the chemical communication and underlining chemoreception mechanism in social insects.

Museum samples reveal rapid evolution by wild honey bees exposed to a novel parasite.

Understanding genetic changes caused by novel pathogens and parasites can reveal mechanisms of adaptation and genetic robustness. Using whole-genome sequencing of museum and modern specimens, we describe the genomic changes in a wild population of honey bees in North America following the introduction of the ectoparasitic mite, Varroa destructor. Even though colony density in the study population is the same today as in the past, a major loss of haplotypic diversity occurred, indicative of a drastic mitochondrial bottleneck, caused by massive colony mortality. In contrast, nuclear genetic diversity did not change, though hundreds of genes show signs of selection. The genetic diversity within each bee colony, particularly as a consequence of polyandry by queens, may enable preservation of genetic diversity even during population bottlenecks. These findings suggest that genetically diverse honey bee populations can recover from introduced diseases by evolving rapid tolerance, while maintaining much of the standing genetic variation.

A first look at the Oxford Nanopore MinION sequencer.

Oxford Nanopore's third-generation single-molecule sequencing platform promises to decrease costs for reagents and instrumentation. After a 2-year hiatus following the initial announcement, the first devices have been released as part of an early access program. We explore the performance of this platform by resequencing the lambda phage genome, and amplicons from a snake venom gland transcriptome. Although the handheld MinION sequencer can generate more than 150 megabases of raw data in one run, at most a quarter of the resulting reads map to the reference, with less than average 10% identity. Much of the sequence consists of insertion/deletion errors, or is seemingly without similarity to the template. Using the lambda phage data as an example, although the reads are long, averaging 5 kb, at best 890 ± 1932 bases per mapped read could be matched to the reference without soft clipping. In the course of a 36 h run on the MinION, it was possible to resequence the 48 kb lambda phage reference at 16× coverage. Currently, substantially larger projects would not be feasible using the MinION. Without increases in accuracy, which would be required for applications such as genome scaffolding and phasing, the current utility of the MinION appears limited. Library preparation requires access to a molecular laboratory, and is of similar complexity and cost to that of other next-generation sequencing platforms. The MinION is an exciting step in a new direction for single-molecule sequencing, though it will require dramatic decreases in error rates before it lives up to its promise.

Astragalus saponins induce growth inhibition and apoptosis in human colon cancer cells and tumor xenograft.

Astragalus memebranaceus is used as immunomodulating agent in treating immunodeficiency diseases and to alleviate the adverse effects of chemotherapeutic drugs. In recent years, it has been proposed that Astragalus may possess anti-tumorigenic potential in certain cancer cell types. In this study, the anti-carcinogenic effects of Astragalus saponin extract were investigated in HT-29 human colon cancer cells and tumor xenograft. Our findings have shown that Astragalus saponins (AST) inhibit cell proliferation through accumulation in S phase and G2/M arrest, with concomitant suppression of p21 expression and inhibition of cyclin-dependent kinase activity. Besides, AST promotes apoptosis in HT-29 cells through caspase 3 activation and poly(ADP-ribose) polymerase cleavage, which is indicated by DNA fragmentation and nuclear chromatin condensation. Nevertheless, we also demonstrate the anti-tumorigenic effects of AST in vivo, of which the reduction of tumor volume as well as pro-apoptotic and anti-proliferative effects in HT-29 nude mice xenograft are comparable with that produced by the conventional chemotherapeutic drug 5-fluorouracil (5-FU). In addition, the side effects (body weight drop and mortality) associated with the drug combo 5-FU and oxaliplatin are not induced by AST. These results indicate that AST could be an effective chemotherapeutic agent in colon cancer treatment, which might also be used as an adjuvant in combination with other orthodox chemotherapeutic drugs to reduce the side effects of the latter compounds.

Effect of sinomenine on gene expression of the IL-1 beta-activated human synovial sarcoma.

Sinomenine is an alkaloid with pharmacological effects of anti-inflammation, anti-angiogenesis, anti-arthritis and immunosuppression. This study aimed to investigate the effect of sinomenine on gene expression of human synovial sarcoma cells (Hs701.T) activated by IL-1 beta. The proliferative effect of sinomenine was examined in the presence or absence of IL-1 beta by the [3H]-thymidine incorporation and MTT assay, respectively. Using DNA microarray technology and RT-PCR, the activating action of IL-1 beta and modulatory effect of sinomenine on Hs701.T were simultaneously determined. Results showed that IL-1 beta could stimulate the proliferation and gene expression of Hs701.T cells. Sinomenine could significantly inhibit proliferation of IL-1 beta-activated Hs701.T cells and suppress expression of 17 genes including IL-6, PlGF, Daxx, and HSP27. These genes were found to be important in tumor progression through the mediation of inflammation, cell adhesion, proliferation, apoptosis and angiogenesis. In conclusion, our study provides supplementary information for the further studies on the pharmacological effects of sinomenine acting on synovial sarcoma.