Project description:Background: Germ-free or axenic organisms are valuable tools for studying immunity, digestion, and development in different hosts. Although most of these studies have been conducted on mice, recently, germ-free invertebrate models (e.g. Drosophila and Apis) are used due to their easy husbandry, low cost for production, maintenance and the high number of individuals per generation they produce. However, a limitation of using these insects is the simple bacterial community present in their guts. The gut of the American cockroach Periplaneta americana displays a complex gut bacterial community composed of hundreds of species. Using P. americana, we developed a germ-free omnivorous invertebrate model to investigate how gut bacteria stimulate and shape normal gut development and metabolism. To determine if the insect host is directly affected by the presence of specific members of their bacterial community, gnotobiotic cockroaches were generated by inoculating a set of various P. americana gut-endemic Gram-negative (Bacteroidetes; n=11) and Gram-positive (Firmicutes; n=2) bacterial strains into germ-free insects. Additionally, we were able to recover the ‘normal’ bacterial-induced gut phenotype by co-housing germ-free cockroaches with wildtype P. americana to produce gut-bacteria conventionalized insects. Changes in gene expression profiles from two distinct regions (midgut and hindgut) of P. americana guts were quantified by RNA-Seq analysis of the germfree, gnotobiotic and conventionalized insects. Basic transcriptomics description: High-resolution transcriptome profiling of germ-free, gnotobiotic, and conventionalized treated P. americana midgut and hindguts. Ca. 43 million reads were obtained for each treatment. A de-novo assembly of all sequence reads was performed by Trinity assembler. Transcriptome assembly yielded 369,082 gene models and 554,155 isoforms. After running Trinotate pipeline, 65,047 (12 %) these transcripts matched an annotated product in at least one of the reference databases used (Uniprot, pfam, KEGG, COG). Additionally, 1,008 putative bacterial genes were annotated in the P. americana genome and ultimately excluded from these analyses. After bacteria decontamination, 553,147 assembled isoforms were used for transcript quantification and differential expression analysis using the DESeq2 pipeline. DESeq2 analysis detected 6,730 and 3,958 differentially expressed transcripts among the germ-free, gnotobiotic and conventionalized treatments in P. americana hindgut and midgut, respectively.
Project description:In the fire ant Solenopsis invicta, a colony queen number is determined by the founding queen's genotypes at the 13 Mb supergene with the non-recombining variants SB and Sb. Single-queen colonies are always headed by SB/SB queens while multiple-queens colonies are always headed by SB/Sb queens. The two variants of the supergene, SB and Sb are completely linked to the two alleles (B and b) of the gene Gp-9. SB/SB and SB/Sb queens differ in many physiological traits including their maturation rate and odor. To explain why SB/SB and SB/Sb queens have different odors, and why SB/SB virgins mature faster and accumulate more fat, we measured expression of ~6000 genes in virgin queens 1 and 11 days after eclosion and in reproductive queens. Keywords: fire ants, Solenopsis invicta, Supergene, queen, Gp-9, social form, maturation, fat storage, queen odor, cuticular hydrocarbon, worker discrimination, monogyne, polygyne, transposon, chemical signaling