Dataset Information

Identification of transcription factor genes involved in anthocyanin biosynthesis in carrot (Daucus carota L.) using RNA-Seq.

ABSTRACT:

Background

Anthocyanins are water-soluble colored flavonoids present in multiple organs of various plant species including flowers, fruits, leaves, stems and roots. DNA-binding R2R3-MYB transcription factors, basic helix-loop-helix (bHLH) transcription factors, and WD40 repeat proteins are known to form MYB-bHLH-WD repeat (MBW) complexes, which activates the transcription of structural genes in the anthocyanin pathway. Although black cultivars of carrots (Daucus carota L.) can accumulate large quantities of anthocyanin in their storage roots, the regulatory genes responsible for their biosynthesis are not well characterized. The current study aimed to analyze global transcription profiles based on RNA sequencing (RNA-Seq), and mine MYB, bHLH and WD40 genes that may function as positive or negative regulators in the carrot anthocyanin biosynthesis pathways.

Results

RNA was isolated from differently colored calli, as well as tissue samples from taproots of various black carrot cultivars across the course of development, and gene expression levels of colored and non-colored tissue and callus samples were compared. The expression of 32 MYB, bHLH and WD40 genes were significantly correlated with anthocyanin content in black carrot taproot. Of those, 11 genes were consistently up- or downregulated in a purple color-specific manner across various calli and cultivar comparisons. The expression of 10 out of these 11 genes was validated using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

Conclusions

The results of this study provide insights into regulatory genes that may be responsible for carrot anthocyanin biosynthesis, and suggest that future focus on them may help improve our overall understanding of the anthocyanin synthesis pathway.

SUBMITTER: Kodama M

PROVIDER: S-EPMC6225646 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Publications

Identification of transcription factor genes involved in anthocyanin biosynthesis in carrot (Daucus carota L.) using RNA-Seq.

Kodama Miyako M Brinch-Pedersen Henrik H Sharma Shrikant S Holme Inger Bæksted IB Joernsgaard Bjarne B Dzhanfezova Tsaneta T Amby Daniel Buchvaldt DB Vieira Filipe Garrett FG Liu Shanlin S Gilbert M Thomas P MTP

BMC genomics 20181108 1

<h4>Background</h4>Anthocyanins are water-soluble colored flavonoids present in multiple organs of various plant species including flowers, fruits, leaves, stems and roots. DNA-binding R2R3-MYB transcription factors, basic helix-loop-helix (bHLH) transcription factors, and WD40 repeat proteins are known to form MYB-bHLH-WD repeat (MBW) complexes, which activates the transcription of structural genes in the anthocyanin pathway. Although black cultivars of carrots (Daucus carota L.) can accumulate ...[more]

PMID: 30409110

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Project description:Purple carrots can accumulate large quantities of anthocyanins in their roots and -in some genetic backgrounds- petioles, and therefore they represent an excellent dietary source of antioxidant phytonutrients. In a previous study, using linkage analysis in a carrot F2 mapping population segregating for root and petiole anthocyanin pigmentation, we identified a region in chromosome 3 with co-localized QTL for all anthocyanin pigments of the carrot root, whereas petiole pigmentation segregated as a single dominant gene and mapped to one of these "root pigmentation" regions conditioning anthocyanin biosynthesis. In the present study, we performed fine mapping combined with gene expression analyses (RNA-Seq and RT-qPCR) to identify candidate genes controlling anthocyanin pigmentation in the carrot root and petiole. Fine mapping was performed in four carrot populations with different genetic backgrounds and patterns of pigmentation. The regions controlling root and petiole pigmentation in chromosome 3 were delimited to 541 and 535 kb, respectively. Genome wide prediction of transcription factor families known to regulate the anthocyanin biosynthetic pathway coupled with orthologous and phylogenetic analyses enabled the identification of a cluster of six MYB transcription factors, denominated DcMYB6 to DcMYB11, associated with the regulation of anthocyanin biosynthesis. No anthocyanin biosynthetic genes were present in this region. Comparative transcriptome analysis indicated that upregulation of DcMYB7 was always associated with anthocyanin pigmentation in both root and petiole tissues, whereas DcMYB11 was only upregulated with pigmentation in petioles. In the petiole, the level of expression of DcMYB11 was higher than DcMYB7. DcMYB6, a gene previously suggested as a key regulator of carrot anthocyanin biosynthesis, was not consistently associated with pigmentation in either tissue. These results strongly suggest that DcMYB7 is a candidate gene for root anthocyanin pigmentation in all the genetic backgrounds included in this study. DcMYB11 is a candidate gene for petiole pigmentation in all the purple carrot sources in this study. Since DcMYB7 is co-expressed with DcMYB11 in purple petioles, the latter gene may act also as a co-regulator of anthocyanin pigmentation in the petioles. This study provides linkage-mapping and functional evidence for the candidacy of these genes for the regulation of carrot anthocyanin biosynthesis.

Project description:BackgroundCarrots (Daucus carota L.) are among the 10 most economically important vegetable crops grown worldwide. Purple carrot cultivars accumulate rich cyanidin-based anthocyanins in a light-independent manner in their taproots whereas other carrot color types do not. Anthocyanins are important secondary metabolites in plants, protecting them from damage caused by strong light, heavy metals, and pathogens. Furthermore, they are important nutrients for human health. Molecular mechanisms underlying anthocyanin accumulation in purple carrot cultivars and loss of anthocyanin production in non-purple carrot cultivars remain unknown.ResultsThe taproots of the three purple carrot cultivars were rich in anthocyanin, and levels increased during development. Conversely, the six non-purple carrot cultivars failed to accumulate anthocyanins in the underground part of taproots. Six novel structural genes, CA4H1, CA4H2, 4CL1, 4CL2, CHI1, and F3'H1, were isolated from purple carrots. The expression profiles of these genes, together with other structural genes known to be involved in anthocyanin biosynthesis, were analyzed in three purple and six non-purple carrot cultivars at the 60-day-old stage. PAL3/PAL4, CA4H1, and 4CL1 expression levels were higher in purple than in non-purple carrot cultivars. Expression of CHS1, CHI1, F3H1, F3'H1, DFR1, and LDOX1/LDOX2 was highly correlated with the presence of anthocyanin as these genes were highly expressed in purple carrot taproots but not or scarcely expressed in non-purple carrot taproots.ConclusionsThis study isolated six novel structural genes involved in anthocyanin biosynthesis in carrots. Among the 13 analyzed structural genes, PAL3/PAL4, CA4H1, 4CL1, CHS1, CHI1, F3H1, F3'H1, DFR1, and LDOX1/LDOX2 may participate in anthocyanin biosynthesis in the taproots of purple carrot cultivars. CHS1, CHI1, F3H1, F3'H1, DFR1, and LDOX1/LDOX2 may lead to loss of light-independent anthocyanin production in orange and yellow carrots. These results suggest that numerous structural genes are involved in anthocyanin production in the taproots of purple carrot cultivars and in the loss of anthocyanin production in non-purple carrots. Unexpressed or scarcely expressed genes in the taproots of non-purple carrot cultivars may be caused by the inactivation of regulator genes. Our results provide new insights into anthocyanin biosynthesis at the molecular level in carrots and for other root vegetables.

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Dataset Information

Identification of transcription factor genes involved in anthocyanin biosynthesis in carrot (Daucus carota L.) using RNA-Seq.

Background

Results

Conclusions

Publications

Identification of transcription factor genes involved in anthocyanin biosynthesis in carrot (Daucus carota L.) using RNA-Seq.

Similar Datasets

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