Abstract

Carrots ( Daucus carota L.) are plants rich in carotenoids, which are mainly stored in special plastids called chromoplasts. Fibrillin (FBN), a plastid lipid-associated protein, is involved in the structural composition of plastids and plays an important role in the storage of carotenoids. In this study, seven DcFBN genes were identified based on the carrot transcriptome and genome database distributing on 7 chromosomes, with molecular weight between 23.77 ~ 65.32 kDa and isoelectric point between 4.58 and 9.52. The 43 FBN proteins derived from 5 plant species were classified into 7 groups by conducting phylogenetic, conserved motif and gene structure analyses. In the analysis of promoter cis -acting elements, it was found that the promoter regions of DcFBN genes were rich in various light-responsive elements and hormone-responsive elements. In addition, we also compared the changes of promoter activity under different hormone treatments by β-glucuronidase (GUS) histochemical staining and GUS gene quantitative real-time PCR (RT-qPCR). The results showed that the promoter of DcFBN10 had the strongest response to SA treatment, and the expression of GUS reporter gene was significantly increased, reaching 5.79-fold that of the control. RT-qPCR analysis of DcFBN genes showed that the expression levels of most members of DcFBN genes in leaves were higher than that in roots. The expression level in roots was high in yellow, purple and orange varieties, relatively lower in white. This study provided a potential reference for the function of DcFBN gene family, and provided basic information for the follow-up study of the role of DcFBN gene in carotenoid accumulation in chromoplasts.