[Transcriptome analysis of Platycodon grandiflorum at different growth years and discovery of key genes for...

Platycodon grandiflorum is a medicinal and edible medicinal material. Our study is aimed to explore the differences in the gene expression of P. grandiflorum in different growth years, and the expression rules of key genes in the biosynthesis of the main active substances of P. grandiflorum. Illumina Hiseq 4000 sequencing platform was used to sequence the transcriptome of P. grandiflorum in different years. Then, 59 654 unigenes were obtained through filtering, assembly, splicing and bioinformatics analysis of the sequencing data, of which 1 671 unigenes were differentially expressed between at least two samples. The results of cluster analysis showed that there was a great difference in the gene expression of P. grandiflorum from one-year-old to two/three-year-old. There were 1 128 different genes between one-and three-year old P. grandiflorum, and only 57 different genes between two-and three-year-old P. grandiflorum. KEGG enrichment results showed that the differential genes of P. grandiflorum in different years were mainly concentra-ted in the biosynthesis of sesquiterpenes and triterpenes, and the biosynthesis of terpenoid skeletons. In the triterpenoid biosynthesis-related pathways, a total of 15 unigenes were identified, involving 5 enzymes. The expression levels of ACAT, HMGR, FDFT1, SQLE decreased with the increase of the growth year of P. grandiflorum. The expression of HMGS was the highest in the one-year-old P. grandiflorum, followed by the three-year-old sample. This study provides useful data for the development of P. grandiflorum, and also provides a basis for the study of related genes in the biosynthetic pathway of platycodin.