Abstract:

Toona sinensis‘Heiyouchun’sprouts were rich in terpenoids that were mainly composed
of sesquiterpenoids such as dehydroaromadendrene，9,10-dehydroisolongifolene，and β-caryophyllene，
their contents were as high as 4 440.71，1 932.02 and 1 799.89 ng · g-1，respectively. To understand
terpenoids biosynthetic pathway，high-through RNA-seq technology was used to genernate the
transcriptome of Toona sinensis‘Heiyouchun’sprout and high-quality base data of 4.70 Gb and 86 870 transcripts were acquired. Furthermore，a total of 55 850 unigenes with average length of 1 013 bp was
obtained by de novo assembly. Sequence alignment analysis showed 39 408 unigenes in our transcriptomic
data had sequence homology with those of other species at different degrees and the highest matching ratio
of functional annotation to Citrus sinensis. Gene ontology analysis revealed that annotated 19 704 unigenes
were grouped into 54 different categories in terms of cellular component，molecular function and
biological process. Among them，the unigenes involved in metabolic process，cell composition，binding
and catalytic activity，and cell processes were predominant. Based on the cluster of orthologous groups，
14 186 unigenes were further annotated and grouped into 25 functional categories. Moreover，28 400 unigenes
were annotated to 135 KEGG pathway and broadly divided into 6 categories of 21 branches. Our data
indicated that 467 unigenes were mined and involved in terpenoids biosynthesis related to flavor formation
of Toona sinensis‘Heiyouchun’sprout，including 226 for terpenoid backbone biosynthesis，71 for
monoterpenoids biosynthesis ， 86 for sesquiterpenoids and triterpenoids biosynthesis ， and 84 for
diterpenoids biosynthesis，which laid a solid foundation for further study on the function of genes related
to terpenoids biosynthesis and the molecular mechanism of flavor compounds formation.

Key words: Toona sinensis, transcriptome, gene annotation, terpenoids metabolism