Project description:The Pacific oyster (Crassostrea gigas) is a kind of marine bivalve of great economic and ecological importance and is among the animals possessing the highest level of genome DNA variations. Despite large efforts made for the discovery of Pacific oyster SNPs in many research groups, challenge still remains as how to utilize SNPs in a high-throughput, transferable and economical manner. In the study, we constructed an oyster 190K SNP array with Affymetrix Axiom genotyping technology. A total of 190,420 SNPs were designed on the chip, which were selected from 54 M SNPs identified by re-sequencing of more than 400 Pacific oysters. Genotyping results from 96 wild oysters indicated that 133,984 (70.4%) SNPs were polymorphic and successfully converted on the chip. Carrying 133K polymorphic SNPs, the oyster 190K SNP array is the first high density SNP chip with the largest throughput currently in mollusc and is commercially available to the worldwide research community.
Project description:Although the importance of host plant chemistry in plant-insect interactions is widely accepted, the genetic basis of adaptation to host plants is poorly understood. Here, we investigate transcriptional changes associated with a host plant shift in Drosophila mettleri. While D. mettleri is distributed mainly throughout the Sonoran Desert where it specializes on columnar cacti (Carnegiea gigantea and Pachycereus pringleii), a population on Santa Catalina Island has shifted to coastal prickly pear cactus (Opuntia littoralis). We compared gene expression of larvae from the Sonoran Desert and Santa Catalina Island when reared on saguaro (C. gigantea), coastal prickly pear, and laboratory food. Consistent with expectations based on the complexity and toxicity of cactus relative to laboratory food, within population comparisons between larvae reared on these food sources revealed transcriptional differences in detoxification and other metabolic pathways. The majority of transcriptional differences between populations on the cactus hosts were independent of the rearing environment, and included a disproportionate number of genes involved in processes relevant to host plant adaptation (e.g. detoxification, central metabolism, and chemosensory pathways). Comparisons of transcriptional reaction norms between the two populations revealed extensive shared plasticity that likely allowed colonization of coastal prickly pear on Santa Catalina Island. We also found that while plasticity may have facilitated subsequent adaptive divergence in gene expression between populations, the majority of genes that differed in expression on the novel host were not transcriptionally plastic in the presumed ancestral state. mRNA profiles of third instar larvae from two different populations reared on three food types was sequenced on two lanes of an Illumina HiSeq 2000 Please note that the de novo assembly gives names to transcripts with the following convention: compXXX_cX_seqX. The first two identifiers (compXX_cX) are equivalent to a gene while the 'seq' identifier might refer to different isoforms or splice variants, etc. Therefore, for example, a gene might be comp123_c0, and this could have multiple sequences corresponding to different isoforms or splice variants. Since the analysis was carried out at the gene level, the program internally merged the multiple sequences together for each gene to generate the count matrix (AllGenesint.counts.matrix.txt) (i.e. it only includes comp123_c0), while the file from the assembly (i.e. Trinity.fasta) also include the individual sequences with the 'seq' identifier.
Project description:The systematic deep sequencing analysis provided a comprehensive understanding of the transcriptome complexity of 2n and 3n Fujian oyster. This information broadens our understanding of the mechanisms of C.angulata polyploidization and contributes to molecular and genetic research by enriching the oyster database. This is the first report on genome-wide transcriptional analysis of adductor muscle of diploid and triploid Fujian oyster and has demonstrated triploid oysters are morphologically almost identical to their diploid counterparts, but have faster growth, due to the reorientation of energetic allocation from gametogenesis to somatic investment. This study provides a foundation for further analysis of the gene expression patterns and signaling pathways which regulate the molecular mechanisms of diploid and triploid oyster.
Project description:The soybean (Glycine max) seed coat has distinctive, genetically programmed patterns of pigmentation and the recessive k1 mutation can epistatically overcome the dominant I and i-i alleles, which inhibit seed color by producing small interfering RNAs (siRNAs) targeting chalcone synthase (CHS) mRNAs. Small RNA sequencing of dissected regions of immature seed coats demonstrated that CHS siRNA levels cause the patterns produced by the i-i and i-k alleles of the I locus, which restrict pigment to the hilum or saddle region of the seed coat, respectively. To identify the K1 locus, we compared RNA-Seq data from dissected regions of two Clark isolines having similar saddle phenotypes mediated by CHS siRNAs but different genotypes (homozygous i-k K1 versus homozygous i-i k1). By examining differentially expressed genes, mapping information, and genome resequencing, we identified a 129-bp deletion in Glyma.11G190900 encoding Argonaute5 (AGO5), a member of the Argonaute family. Amplicon sequencing of several independent saddle pattern mutants from different genetic backgrounds revealed independent lesions affecting AGO5, thus establishing Glyma.11G190900 as the K1 locus. Non-functional AGO5 from k1 alleles leads to altered distributions of CHS siRNAs, thus explaining how the k1 mutation reverses the phenotype of the seed coat regions from yellow to pigmented, even in the presence of the normally dominant I or i-i alleles.
Project description:Hox and ParaHox genes encode transcription factors with conserved similar expression patterns in divergent animals. The Pdx (Xlox) homeobox gene, for example, is expressed in a sharp spatial domain in the endodermal cell layer of the gut in chordates, echinoderms, annelids and molluscs. The significance of comparable gene expression patterns is unclear because it is not known if downstream transcriptional targets are also conserved. We thus conducted experiments to show that a classic transcriptional target of Pdx1 in vertebrates, the insulin gene, is also a direct target of Pdx in the Pacific oyster. We report that oyster has a diversity of insulin-related genes including one co-expressed with Pdx in the endodermal layer of oyster digestive tissue. Transcriptome analysis reveals functional similarity of this tissue to vertebrate pancreas. Using ATAC-seq we identify a Pdx homeodomain binding site upstream of the endodermally-expressed oyster insulin-related gene and using cell culture demonstrate that oyster Pdx acts as a transcriptional activator through this site. These data argue that a classic homeodomain-target gene interaction dates back to the base of Bilateria.