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:Although pear is an important edible fruit species, the current available genomic information is limited. Combining the Solexa/ Illumina RNA-seq high-throughput sequencing approach with Digital Gene Expression (DGE) analysis results in a powerful transcriptomic study. This publication reports the transcriptome profiling analysis of Pyrus bretschneideri Rehd. using RNA-seq and DGE in order to better understand the molecular mechanisms underlying biological aspects of pear, especially fruit development and maturation.Using high-throughput Illumina RNA-seq combined with a tag-based Digital Gene Expression (DGE) system, de novo transcriptome assembly and gene expression analysis of P. bretschneideri were performed at an unprecedented depth (5.47 gigabase pairs). Approximately 60.77 million reads were obtained, trimmed, and assembled into 90,227 unigenes. The unigenes comprised 17,619 contig clusters and 72,608 singletons and were an average length of 508 bp and had an N50 of 635 bp. Sequence similarity analyses against six public databases (Uniprot, NR and COGs at NCBI, Pfam, InterPro and KEGG) found 61,636 unigenes that could be annotated with gene descriptions, conserved protein domains, or gene ontology terms. 34.6% of the unigenes (31,215) were annotated against KEGG into 121 known metabolic or signaling pathways. DGE libraries of five different developmental fruit stages were constructed and analyzed, and the gene expression variations between two consecutive stages were compared. Thousands of genes showed significantly different expression levels based on the various comparisons. Extensive transcriptome and DGE profiling data have been obtained from the deep sequencing of the Chinese white pear, which can serve as an important public information platform for gene expression, genomic, and functional genomic studies in P. bretschneideri and which provides comprehensive gene expression information at the transcriptional level that could facilitate understanding of the molecular mechanisms in fruit development and maturation.

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