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Tung oil, the major product of tung tree ( Vernicia fordii) seeds, is one of the highest quality oils for industrial applications and has been considered for the production of biodiesel. Considering the poor agronomical traits of this crop, efforts have been made to breed tung trees for a higher fruit yield and oil property modification for biodiesel use or to engineer plants to produce a higher tung oil yield. However, these efforts have been hampered by a lack of molecular information, as there is no available genome and identified and characterized transcripts of this tree are scarce. Furthermore, there are still many knowledge gaps regarding tung oil biosynthesis. To provide a comprehensive and accurate foundation for molecular studies of tung tree, we present here a reference transcriptome dataset of mature tung seeds. A set of 43,081,927 reads were assembled into 47,585 unigenes. A homology search using blastx against the GenBank nonredundant protein database and the Swiss-Prot database resulted in the annotation of 96 and 81 % of these unigenes, respectively. We also systematically arranged a series of unigenes potentially associated with oil biosynthesis and degradation and examined the expression profile of a subset of those genes in samples from five different stages of seed development, providing a valuable source of genes and transcriptional information related to these pathways. This study represents the first large-scale transcriptome annotation of tung tree and will be useful in tung breeding for oil properties and other agronomical traits. [ABSTRACT FROM AUTHOR]

The tung tree is an important non-edible oilseed source and consists of two species Vernicia fordii and Vernicia montana native to southern China and southeast Asia. In this study, the frequency and distribution of simple sequence repeats (SSRs) in expressed sequence tags (ESTs) of V. fordii were characterized based on 2,407 available EST sequences from the National Center for Biotechnology Information database. Twenty-two EST-SSR markers were developed by screening the genomic DNAs of six individuals of V. fordii from three accessions and 120 individuals of V. montana from 30 indigenous V. montana accessions collected from different geographic areas in southwestern China and northern Laos. The 22 EST-SSR markers exhibited a moderate level of polymorphism in V. montana with an average of 3.36 alleles per locus and PIC of 0.401. Genetic relatedness investigation showed that there was not only distinct genetic differentiation among tung trees but also a distinct geographic pattern among V. montana accessions. The current study is the first report of the development of EST-SSRs and genetic relatedness investigation in tung trees. These EST-SSR markers reported here will be valuable resources for future genetic studies, like construction of linkage maps, diversity analysis, quantitative trait locus/association mapping, and molecular breeding of the tung tree. The genetic relatedness identified in V. montana would provide potential clues in choosing germplasms in interest as progenitors for cross breeding and variety improvement of V. montana in practice. [ABSTRACT FROM AUTHOR]