Project description:<p><strong>BACKGROUND:</strong> Plants exhibit wide chemical diversity due to the production of specialized metabolites that function as pollinator attractants, defensive compounds, and signaling molecules. Lamiaceae (mints) are known for their chemodiversity and have been cultivated for use as culinary herbs, as well as sources of insect repellents, health-promoting compounds, and fragrance.</p><p><strong>FINDINGS:</strong> We report the chromosome-scale genome assembly of Callicarpa americana L. (American beautyberry), a species within the early-diverging Callicarpoideae clade of Lamiaceae, known for its metallic purple fruits and use as an insect repellent due to its production of terpenoids. Using long-read sequencing and Hi-C scaffolding, we generated a 506.1-Mb assembly spanning 17 pseudomolecules with N50 contig and N50 scaffold sizes of 7.5 and 29.0 Mb, respectively. In all, 32,164 genes were annotated, including 53 candidate terpene synthases and 47 putative clusters of specialized metabolite biosynthetic pathways. Our analyses revealed 3 putative whole-genome duplication events, which, together with local tandem duplications, contributed to gene family expansion of terpene synthases. Kolavenyl diphosphate is a gateway to many of the bioactive terpenoids in C. americana; experimental validation confirmed that CamTPS2 encodes kolavenyl diphosphate synthase. Syntenic analyses with Tectona grandis L. f. (teak), a member of the Tectonoideae clade of Lamiaceae known for exceptionally strong wood resistant to insects, revealed 963 collinear blocks and 21,297 C. americana syntelogs.</p><p><strong>CONCLUSIONS:</strong> Access to the C. americana genome provides a road map for rapid discovery of genes encoding plant-derived agrichemicals and a key resource for understanding the evolution of chemical diversity in Lamiaceae.</p>
Project description:Long-read genome assemblies for three species within the D. virilis sub-group: D. virilis, D. novamexicana, and D. americana Assembly
Project description:For many organisms the ability to cold acclimate with the onset of seasonal cold has major implications for their fitness. In insects, where this ability is widespread, the physiological changes associated with increased cold tolerance have been well studied. Despite this, little work has been done to trace changes in gene expression during cold acclimation that lead to an increase in cold tolerance. We used an RNA-Seq approach to investigate this in two species of the Drosophila virilis group. We found that the majority of genes that are differentially expressed during cold acclimation differ between the two species. Despite this, the biological processes associated with the differentially expressed genes were broadly similar in the two species. These included: metabolism, cell membrane composition, and circadian rhythms, which are largely consistent with previous work on cold acclimation / cold tolerance. In addition, we also found evidence of the involvement of the rhodopsin pathway in cold acclimation, a pathway that has been recently linked to thermotaxis. Interestingly, we found no evidence of differential expression of stress genes implying that long-term cold acclimation and short-term stress response may have a different physiological basis.
Project description:For many organisms the ability to cold acclimate with the onset of seasonal cold has major implications for their fitness. In insects, where this ability is widespread, the physiological changes associated with increased cold tolerance have been well studied. Despite this, little work has been done to trace changes in gene expression during cold acclimation that lead to an increase in cold tolerance. We used an RNA-Seq approach to investigate this in two species of the Drosophila virilis group. We found that the majority of genes that are differentially expressed during cold acclimation differ between the two species. Despite this, the biological processes associated with the differentially expressed genes were broadly similar in the two species. These included: metabolism, cell membrane composition, and circadian rhythms, which are largely consistent with previous work on cold acclimation/cold tolerance. In addition, we also found evidence of the involvement of the rhodopsin pathway in cold acclimation, a pathway that has been recently linked to thermotaxis. Interestingly, we found no evidence of differential expression of stress genes implying that long-term cold acclimation and short-term stress response may have a different physiological basis.
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:Prezygotic isolation mechanisms, particularly courtship behavior, play a significant role in the formation of reproductive barriers. The action of these mechanisms leads to the coexistence of numerous closely related insect species with specific adaptations in a shared or adjacent territory. The genetic basis of these mechanisms has been studied using closely related Drosophila species, such as the D. virilis group. However, the investigation of individual courtship behavior elements has been limited until recently, and the effect of genotype on the species-specific features of courtship as a whole has not been thoroughly examined. It should be noted that courtship behavior is not a typical quantitative trait that can be easily measured or quantified in both females and males, similar to traits like wing length or bristle number. Each courtship element involves the participation of both female and male partners, making the genetic analysis of this behavior complex. As a result, the traditional approach of genetic analysis for quantitative traits, which involves variance decomposition in a set of crosses, including parental species, F1 and F2 hybrids, and backcrosses of F1 to parental species, is not suitable for analyzing courtship behavior. To address this, we employed a modified design by introducing what we refer to as 'reference partners' during the testing of hybrid individuals from F1, F2, and backcrosses. These reference partners represented one of the parental species. This approach allowed us to categorize all possible test combinations into four groups based on the reference partner's sex (female or male) and their constant genotype towards one of the parental species (D. virilis or D. americana). The genotype of the second partner in the within-group test combinations varied from completely conspecific to completely heterospecific, based on the parental chromosomal sets. To assess the contribution of partner genotypes to the variability of courtship-element parameters, we employed structural equation modeling (SEM) instead of the traditional analysis of variance (ANOVA). SEM enabled us to estimate the regression of the proportion of chromosomes of a specific species type on the value of each courtship-element parameter in partners with varying genotypes across different test combinations. The aim of the current study was to analyze the involvement of sex chromosomes and autosomes in the formation of courtship structure in D. virilis and D. americana. The genetic analysis was complemented by video recording and formalization of courtship-ritual elements. D. virilis was found to be more sensitive to mate stimuli compared to D. americana. The majority of species-specific parameters, such as latency and duration of courtship elements (e.g., male and female song, following, licking, and circling), were shown to be influenced by the D. virilis genotype. However, not all of these parameters significantly impact copulation success, with the male song, licking, and following being the most significant. In females, the female song was found to have a significant relationship only with copulation duration. The influence of the female genotype on the species-specific parameters of courtship elements is primarily related to autosomes, while the male genotype is associated with the X chromosomes. The study suggests that sexual selection primarily occurs through acoustic and chemoreceptor channels.