title: Transcriptome sequencing and identification of cold tolerance genes in hardy Corylus species (C. heterophylla Fisch) floral buds.
abstract: BACKGROUND
  The genus Corylus is an important woody species in Northeast China. Its products, hazelnuts, constitute one of the most important raw materials for the pastry and chocolate industry. However, limited genetic research has focused on Corylus because of the lack of genomic resources. The advent of high-throughput sequencing technologies provides a turning point for Corylus research. In the present study, we performed de novo transcriptome sequencing for the first time to produce a comprehensive database for the Corylus heterophylla Fisch floral buds.
  
  
  RESULTS
  The C. heterophylla Fisch floral buds transcriptome was sequenced using the Illumina paired-end sequencing technology. We produced 28,930,890 raw reads and assembled them into 82,684 contigs. A total of 40,941 unigenes were identified, among which 30,549 were annotated in the NCBI Non-redundant (Nr) protein database and 18,581 were annotated in the Swiss-Prot database. Of these annotated unigenes, 25,311 and 10,514 unigenes were assigned to gene ontology (GO) categories and clusters of orthologous groups (COG), respectively. We could map 17,207 unigenes onto 128 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG) database. Additionally, based on the transcriptome, we constructed a candidate cold tolerance gene set of C. heterophylla Fisch floral buds. The expression patterns of selected genes during four stages of cold acclimation suggested that these genes might be involved in different cold responsive stages in C. heterophylla Fisch floral buds.
  
  
  CONCLUSIONS
  The transcriptome of C. heterophylla Fisch floral buds was deep sequenced, de novo assembled, and annotated, providing abundant data to better understand the C. heterophylla Fisch floral buds transcriptome. Candidate genes potentially involved in cold tolerance were identified, providing a material basis for future molecular mechanism analysis of C. heterophylla Fisch floral buds tolerant to cold stress.
authors.affiliation: Shandong Institute of Pomology, Shandong Provincial Key Laboratory of Fruit Tree Biotechnology Breeding, Tai'an, Shandong, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Shandong Institute of Pomology, Shandong Provincial Key Laboratory of Fruit Tree Biotechnology Breeding, Tai'an, Shandong, China.
authors.forename: Qingzhong
authors.initials: Q
authors.lastname: Liu
authors.affiliation: School of Forest Resources and Conservation, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China.
authors.forename: Tiantian
authors.initials: T
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China.
authors.forename: Guixi
authors.initials: G
authors.lastname: Wang
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D002681:China; D003080:Cold Temperature; D031211:Corylus / Q000235:genetics*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D059014:High-Throughput Nucleotide Sequencing; D056626:Inflorescence / Q000235:genetics*; D018895:Microsatellite Repeats; D058977:Molecular Sequence Annotation; D017422:Sequence Analysis, DNA; D059467:Transcriptome