Advances in research on the carrot,an important root vegetable in the Apiaceae family

Carrots(Daucus carota L.),among the most important root vegetables in the Apiaceae family,are cultivated worldwide.The storage root is widely utilized due to its richness in carotenoids,anthocyanins,dietary fiber,vitamins and other nutrients.Carrot extracts,which serve as sources of antioxidants,have important functions in preventing many diseases.The biosynthesis,metabolism,and medicinal properties of carotenoids in carrots have been widely studied.Research on hormone regulation in the growth and development of carrots has also been widely performed.Recently,with the development of high-throughput sequencing technology,many efficient tools have been adopted in carrot research.A large amount of sequence data has been produced and applied to improve carrot breeding.A genome editing system based on CRISPR/Cas9 was also constructed for carrot research.In this review,we will briefly summarize the origins,genetic breeding,resistance breeding,genome editing,omics research,hormone regulation,and nutritional composition of carrots.Perspectives about future research work on carrots are also briefly provided.

Telomere-to-telomere carrot (Daucus carota) genome assembly reveals carotenoid characteristics

Carrot(Daucus carota)is an Apiaceae plant with multi-colored fleshy roots that provides a model system for carotenoid research.In this study,we assembled a 430.40 Mb high-quality gapless genome to the telomere-to-telomere(T2T)level of“Kurodagosun”carrot.In total,36268 genes were identified and 34961 of them were functionally annotated.The proportion of repeat sequences in the genome was 55.3%,mainly long terminal repeats.Depending on the coverage of the repeats,14 telomeres and 9 centromeric regions on the chromosomes were predicted.A phylogenetic analysis showed that carrots evolved early in the family Apiaceae.Based on the T2T genome,we reconstructed the carotenoid metabolic pathway and identified the structural genes that regulate carotenoid biosynthesis.Among the 65 genes that were screened,9 were newly identified.Additionally,some gene sequences overlapped with transposons,suggesting replication and functional differentiation of carotenoid-related genes during carrot evolution.Given that some gene copies were barely expressed during development,they might be functionally redundant.Comparison of 24 cytochrome P450 genes associated with carotenoid biosynthesis revealed the tandem or proximal duplication resulting in expansion of CYP gene family.These results provided molecular information for carrot carotenoid accumulation and contributed to a new genetic resource.

AgMYB1,an R2R3-MYB factor,plays a role in anthocyanin production and enhancement of antioxidant capacity in celery

Celery is rich in nutrients and cultivated worldwide.Anthocyanins are natural plant pigments with high antioxidant capabilities in the human diet.The accumulation of anthocyanins in celery results in the purple skin color of petioles.Here,an R2R3-MYB transcription factor(TFs),AgMYB1,was cloned from purple-skin celery.Phylogenetic analysis revealed that AgMYB1 belongs to the anthocyanin branch.Sequence alignment showed that AgMYB1 contains multiple anthocyanin-related motifs.Consistent with the activating role in anthocyanin production,AgMYB1 showed higher transcriptions in purple celery compared with non-purple celery.Transient expression of AgMYB1 in tobacco leaves promoted the accumulation of anthocyanins and produced red pigments in leaves.Heterologous expression of AgMYB1 in Arabidopsis activates anthocyanin production and generates dark-purple plants.The enhancement of anthocyanin biosynthetic genes transcripts and glycosylation capacities in transgenic Arabidopsis verified the activating roles of AgMYB1 at the gene and protein level,respectively.The antioxidant capacity of transgenic Arabidopsis was also increased compared to wild type Arabidopsis.Additionally,yeast two-hybrid assay proved that AgMYB1 interacted with bHLH TFs to regulate anthocyanin biosynthesis.Our results show that the overexpression of single R2R3-MYB gene,AgMYB1,without coexpression of other TFs,can improve anthocyanin production and antioxidant capacity in transgenic plants.This study presents new information for anthocyanin regulatory mechanisms in purple celery and provides a strategy for cultivating plants with high levels of anthocyanins.