NUDX gene family identification and its potential role in carotenoid biosynthesis of carrot.

Carrot is an important root vegetable crop for its richness in carotenoids and other nutrients. The presence of terpenoids gives carrot a unique flavor and texture. Nudix hydrolases (NUDX) are widely present in living organisms. In plants, the NUDX members were involved in carotenoid biosynthesis, terpenoid metabolism, and plant immune responses. Till now, the little-known function of NUDX members in carrot. In this study, 33 carrot DcNUDX genes were identified and categorized into 9 subgroups based on the preferred substrates. The occurrence of tandem duplication and segmental duplication events facilitated the evolution and expansion of the DcNUDX family. Tertiary structure prediction showed that proteins with close evolutionary relationships had similar tertiary structures. Promoter element analysis of DcNUDX genes revealed their potential regulation by MYB or MYC transcription factors and responsiveness to plant hormones. Transcriptome data revealed that DcNUDX genes exhibited diverse transcript abundance during carrot taproot development. The expression patterns of the carrot homologs of Arabidopsis thaliana chloroplast-localized NUDX genes were detected in different colored carrot taproots. Combined with the prokaryotic expression system in E. coli, DcNUDX14, DcNUDX19a, and DcNUDX23 were preliminarily speculated to potentially influence carotenoid accumulation. This result facilitates further study of the specific functions of NUDX members in carrot.