Transcriptome Characterization For Genome Annotation And Functional Genomics In Pyrus spp

Pear (Pyrus spp.) is one of the leading cultivated temperate fruit crops and grown in different countries around the world. It ranks second after apple, as a deciduous tree fruit species, in commercial production (over 20 million tons per year) . Pear belongs to the subfamily Pomoideae of Rosaceae, and has at least 22 well-recognized primary species as well as several either natural or artificial interspecific hybrids classified as different species. Due to the high level of heterozygosity, the whole genome and transcriptomic sequences of pear have not yet been available until now. In this study, 12 different tissues including leaves, flowers, fruits, stems, and seeds at different stage of development from pear cultivar Dangshansuli (Pyrus bretschneideri Rehd.) were used for cDNA library construction. High-throughput Illumina sequencing and de novo transcriptome assembly were carried out using these cDNA libraries. A total of 7.8 Gb transcriptome reads was generated, and these were assembled into 84,939 unigenes with SOAPdenovo. Profiling of gene expression was used to identify candidate genes associated with formation of sclereids (stone cells) in fruit tissue, as well as sugar and acidity metabolic networks. This combined dataset will be used to annotate the pear genome sequence, serve as a resource to select functional candidate genes for targeted traits and pathways, and to develop EST-SSR markers.