Transcriptome of tung tree mature seeds with an emphasis on lipid metabolism genes

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 ofthis crop, efforts have been made to breed tung trees for ahigher 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 comprehensiveand accurate foundation for molecular studies of tung tree,we present here a reference transcriptome dataset of maturetung seeds. A set of 43,081,927 reads were assembled into 47,585 unigenes. A homology search using blastx againstthe GenBank nonredundant protein database and the Swiss-Prot database resulted in the annotation of 96 and 81 % of these unigenes, respectively. We also systematically arrangeda series of unigenes potentially associated with oil biosynthesisand degradation and examined the expression profileof a subset of those genes in samples from five different stages ofseed development, providing a valuable source of genes and transcriptional information related to these pathways. Thisstudy represents the first large-scale transcriptome annotation of tung tree and will be useful in tung breeding for oil properties and other agronomical traits.