Transcriptome profiling of genes involving in carotenoid biosynthesis and accumulation between leaf and root of carrot (Daucus carota L.).

Carrot provides abundant carotenoid for human diet and is one of the most widely cultivated root vegetables in the world. However, the absence of the tissue-specific transcriptome of carrots hampers the investigation of the association of secondary metabolic mechanism with the different tissue types. In this study, we obtained 46,119,008/48,414,508 raw reads and 45,394,846/47,887,648 clean reads from the carrot leaf and root, respectively. Moreover, α- and β-carotene were found to accumulate in both tissues. Then, using Trinity assembly into contigs and mapped back to contigs, these reads were assembled to 56,267 and 62,427 leaf and root unigenes, respectively, after Ns removal and paired-end extension. In addition, a total of 18,354 DEGs were found between the carrot leaf and root unigenes, and 99 of these DEGs were found to be involved in carotenoid biosynthesis as revealed by integrated function annotation. In the carotenoid pathway DEGs, DcPSY1, DcZ-ISO, DcCISO2, DcLBCY, DcLECY, DcZEP1, DcZEP2, DcVDE1, DcVDE2, DcNSY1, DcNSY2, DcA8H-CYP707A1.2, DcAAO3a, DcCCD4, and DcMAX1 were expressed dramatically in the carrot leaf compared with in the root. This result was consistent with the results from the quantitative real-time PCR analysis of DEG expression profiles. Moreover, 67 more carotenoid biosynthesis-related genes were found in this transcriptome database. Most of these DEGs were up-regulated in the carrot leaf compared with those in the root. The expression of DEGs may be related to the higher carotenoid pathway flux in the carrot leaf than in the root. These results will help to further understand the carotenoid biosynthesis in carrot.