Molecular analysis of anthocyanin-related genes in ornamental cabbage

Transcriptome-Wide Identification and Expression Analysis of bHLH Family Genes in Iris domestica under Drought and Cu Stress

The role of bHLH transcription factors in plant response to abiotic stress and regulation of flavonoid metabolism is well documented. However, to date, the bHLH transcription factor family in Iris domestica remains unreported, impeding further research on flavonoid metabolism in this plant. To address this knowledge gap, we employed bioinformatics to identify 39 IdbHLH genes and characterised their phylogenetic relationships and gene expression patterns under both drought and copper stress conditions. Our evolutionary tree analysis classified the 39 IdbHLHs into 17 subfamilies. Expression pattern analysis revealed that different IdbHLH transcription factors had distinct expression trends in various organs, suggesting that they might be involved in diverse biological processes. We found that IdbHLH36 was highly expressed in all organs (Transcripts Per Million (TPM) > 10), while only 12 IdbHLH genes in the rhizome and four in the root were significantly upregulated under drought stress. Of these, four genes (IdbHLH05, -37, -38, -39) were co-upregulated in both the rhizome and root, indicating their potential role in drought resistance. With regards to copper stress, we found that only 12 genes were upregulated. Further co-expression analysis revealed that most bHLH genes were significantly correlated with key enzyme genes involved in isoflavone biosynthesis. Thereinto, IdbHLH06 showed a significant positive correlation with IdC4H1 and Id4CL1 (p < 0.05). Furthermore, a transient expression assay confirmed that the IdbHLH06 protein was localised in the nucleus. Our findings provide new insights into the molecular basis and regulatory mechanisms of bHLH transcription factors in isoflavone biosynthesis in I. domestica.

Research progress and applications of colorful Brassica crops

MAIN CONCLUSION

We review the application and the molecular regulation of anthocyanins in colorful Brassica crops, the creation of new germplasm resources, and the development and utilization of colorful Brassica crops. Brassica crops are widely cultivated: these include oilseed crops, such as rapeseed, mustards, and root, leaf, and stem vegetable types, such as turnips, cabbages, broccoli, and cauliflowers. Colorful variants exist of these crop species, and asides from increased aesthetic appeal, these may also offer advantages in terms of nutritional content and improved stress resistances. This review provides a comprehensive overview of pigmentation in Brassica as a reference for the selection and breeding of new colorful Brassica varieties for multiple end uses. We summarize the function and molecular regulation of anthocyanins in Brassica crops, the creation of new colorful germplasm resources via different breeding methods, and the development and multifunctional utilization of colorful Brassica crop types.

Genome-wide identification of bHLH transcription factors: Discovery of a candidate regulator related to flavonoid biosynthesis in Erigeron breviscapus

Erigeron breviscapus is a Compositae plant, and its rich flavonoids have shown strong preventative and curative effects in the treatment of cardio- and cerebrovascular diseases. bHLH genes play a crucial role in plant growth and development. There are 116 EbbHLH genes in E. breviscapus, and each gene has been named based on its chromosome location. Our phylogenetic analysis divided these genes into 18 subfamilies. To further investigate its function, EbbHLH80 was isolated from E. breviscapus leaves. Next, transcriptomic and metabolomic analyses of tobacco leaves were performed. Among 421 differentially accumulated compounds, 98 flavonoids were identified. In addition, differentially expressed genes were identified using RNA-seq, and further analysis suggested that EbbHLH80-OE could not only regulate the expression of some structural genes in the flavonoid biosynthesis pathway to achieve flavonoid accumulation but also be involved in the regulation of a series of downstream pathways, such as stress response, ABA and ethylene signal transduction, to affect plant growth and development. The results of our analysis provide new insights into the function of EbbHLH80 and lay the foundation for future functional studies on E. breviscapus.

Development of Novel Markers and Creation of Non-Anthocyanin and Anthocyanin-Rich Broccoli (Brassica oleracea var. italica) Cultivars

In broccoli, anthocyanin pigments can be accumulated in the flower bud epidermis, resulting in a purple-green head. This study aimed to create non-anthocyanin green broccoli varieties and anthocyanin-rich purple broccoli varieties using new F3′H and Pur7.1-K1 molecular markers, respectively. The breeding program started with crosses of the recipient (superior variety and line) LF02 line with the donor line SN60 carrying the recessive allele f3′h and the donor line BT126 carrying the dominant allele Pur7.1. The F1 hybrids were confirmed with molecular markers and backcrossed with the recurrent parent LF02, followed by cycles of foreground and background selection at each stage. A total of 161 green plants with the f3′hf3′h genotype and 152 purple plants with the Pur7.1Pur7.1 genotype were selected from the BC3F2 line. Among these, 34 green plants and 28 purple plants demonstrated >85% background recovery. The identified plants were selfed to obtain 301 green and 416 purple BC3F3 plants for assessment of major agronomic traits. After these investigations, two green broccoli lines without anthocyanin and three anthocyanin-rich purple lines with the best yield/quality characteristics were obtained. The development of these lines might help provide basic materials and the theoretical basis for breeding commercial broccoli varieties.

Comprehensive Transcriptome–Metabolome Analysis and Evaluation of the Dark_Pur Gene from Brassica juncea That Controls the Differential Regulation of Anthocyanins in Brassica rapa

Chinese cabbage (Brassica rapa) is a major vegetable crop in China. The accumulation of anthocyanins improves the quality and flavor of Brassica crops and is beneficial for human health. There has been great research interest in breeding purple Chinese cabbage, for which it is necessary to study the key genes and mechanisms of anthocyanin accumulation. Through distant hybridization between purple mustard (Brassica. juncea) and green Chinese cabbage (B. rapa), purple Chinese cabbage plants were obtained. Furthermore, the Dark_Pur gene was cloned in the purple Chinese cabbage plants, which came from purple mustard and may be responsible for the purple phenotype in purple Chinese cabbage plants. Through particle bombardment of isolated microspores from Chinese cabbage to transform the Dark_Pur gene, the transformed purple Chinese cabbage plant was obtained, thus verifying the function of the Dark_Pur gene. To further study the Dark_Pur gene regulatory mechanism of anthocyanin accumulation in Chinese cabbage, the purple/green Chinese cabbage lines and purple/green mustard lines were subjected to transcriptome–metabolome analysis. Three stages (cotyledon, seedling, and large-leaf stages) of the purple/green Chinese cabbage lines and purple/green mustard lines were selected for analysis. The results indicated that the expression level of the transcription factor genes BraA09g028560.3C, BraA03g019460.3C, and BraA07g035710.3C may be induced by the Dark_Pur gene and they play an important role in purple Chinese cabbage, and BjuB010898 and BjuO006089 may be responsible for anthocyanin accumulation in mustard. Studying the structural genes of the purple Chinese cabbage showed that PAL, C4H, 4CL, CHS, CHI, F3H, F3'H, FLS, DFR, ANS, and UGT were up-regulated in three growth periods. There were 22 and 10 differentially expressed metabolites (DEMs) in seedling and large-leaf stages between purple/green Chinese cabbage, respectively, and 12 and 14 differentially expressed metabolites (DEMs) in seedling and large-leaf stages between purple/green mustard, respectively, which may indicate that the Dark_Pur gene from purple mustard greatly regulates anthocyanin accumulation in purple Chinese cabbage. This study provides a foundation for further elucidating anthocyanin regulation.

Biochemical and transcriptomic analyses reveal that critical genes involved in pigment biosynthesis influence leaf color changes in a new sweet osmanthus cultivar 'Qiannan Guifei'

BACKGROUND

Osmanthus fragrans (Oleaceae) is one of the most important ornamental plant species in China. Many cultivars with different leaf color phenotypes and good ornamental value have recently been developed. For example, a new cultivar 'Qiannan Guifei', presents a rich variety of leaf colors, which change from red to yellow-green and ultimately to green as leaves develop, making this cultivar valuable for landscaping. However, the biochemical characteristics and molecular mechanisms underlying leaf color changes of these phenotypes have not been elucidated. It has been hypothesized that the biosynthesis of different pigments in O. fragrans might change during leaf coloration. Here, we analyzed transcriptional changes in genes involved in chlorophyll (Chl), flavonoid, and carotenoid metabolic pathways and identified candidate genes responsible for leaf coloration in the new cultivar 'Qiannan Guifei'.

METHODS

Leaf samples were collected from 'Qiannan Guifei' plants at the red (R), yellow-green (YG) and green (G) leaf stages. We compared the different-colored leaves via leaf pigment concentrations, chloroplast ultrastructure, and transcriptomic data. We further analyzed differentially expressed genes (DEGs) involved in the Chl, flavonoid, and carotenoid metabolic pathways. In addition, we used qRT-PCR to validate expression patterns of the DEGs at the three stages.

RESULTS

We found that, compared with those at the G stage, chloroplasts at the R and YG stages were less abundant and presented abnormal morphologies. Pigment analyses revealed that the leaves had higher flavonoid and anthocyanin levels at the R stage but lower Chl and carotenoid concentrations. Similarly, Chl and carotenoid concentrations were lower at the YG stage than at the G stage. By using transcriptomic sequencing, we further identified 61 DEGs involved in the three pigment metabolic pathways. Among these DEGs, seven structural genes (OfCHS, OfCHI, OfF3H, OfDFR, OfANS, OfUGT andOf3AT) involved in the flavonoid biosynthesis pathway were expressed at the highest level at the R stage, thereby increasing the biosynthesis of flavonoids, especially anthocyanins. Six putativeOfMYB genes, including three flavonoid-related activators and three repressors, were also highly expressed at the R stage, suggesting that they might coordinately regulate the accumulation of flavonoids, including anthocyanins. Additionally, expressions of the Chl biosynthesis-related genes OfHEMA, OfCHLG and OfCAO and the carotenoid biosynthesis-related genes OfHYB and OfZEP were upregulated from the R stage to the G stage, which increased the accumulation of Chl and carotenoids throughout leaf development. In summary, we screened the candidate genes responsible for the leaf color changes of 'Qiannan Guifei', improved current understanding of the regulatory mechanisms underlying leaf coloration and provided potential targets for future leaf color improvement in O. fragrans.

Regulatory Mechanisms of bHLH Transcription Factors in Plant Adaptive Responses to Various Abiotic Stresses

Basic helix-loop-helix proteins (bHLHs) comprise one of the largest families of transcription factors in plants. They have been shown to be involved in responses to various abiotic stresses, such as drought, salinity, chilling, heavy metal toxicity, iron deficiency, and osmotic damages. By specifically binding to cis-elements in the promoter region of stress related genes, bHLHs can regulate their transcriptional expression, thereby regulating the plant's adaptive responses. This review focuses on the structural characteristics of bHLHs, the regulatory mechanism of how bHLHs are involved transcriptional activation, and the mechanism of how bHLHs regulate the transcription of target genes under various stresses. Finally, as increasing research demonstrates that flavonoids are usually induced under fluctuating environments, the latest research progress and future research prospects are described on the mechanisms of how flavonoid biosynthesis is regulated by bHLHs in the regulation of the plant's responses to abiotic stresses.

Identification of cassava alternative splicing-related genes and functional characterization of MeSCL30 involvement in drought stress

Alternative splicing (AS) is an important post-transcriptional regulation strategy that can increase the proteome diversity and regulate mRNA level in eukaryote. Multi-exon genes can be alternative spliced to generate two or more transcripts, thereby increasing the adaptation to the external stress conditions in planta. However, AS-related proteins were less explored in cassava which is an important staple crop in the tropical area. A total of 365 genes encoding AS-related proteins were identified and renamed in the cassava genome, and the transcriptional and splicing changes of 15 randomly selected genes were systematically investigated in the tissues under diverse abiotic stress conditions. 13 out of 15 genes undergo AS in the tissues and under diverse environmental stress condition. Importantly, the greatest changes of splicing patterns were found in the leaf or in response to temperature stress, indicating that AS-related proteins had their tissue-specific regulation patterns and might be participated in the plant adaptation to temperature stress. We then found that overexpression of MeSCL30 in Arabidopsis enhanced the tolerance to drought stress through maintaining reactive oxygen species (ROS) homeostasis and increasing the expression of drought-responsive genes. Therefore, these findings refined the AS-related protein-coding genes and provided novel insights for manipulation of AS-related genes in order to enhance the resistance to environmental stress in plant.

Transcriptome analysis reveals the mechanism of anthocyanidins biosynthesis during grains development in purple corn (Zea mays L.)

Anthocyanidins are important pigments that cause plant tissues to develop colors. They have attracted much attention due to their crucial regulatory roles in plant growth as well as their health benefits. In order to reveal the molecular mechanism of anthocyanidin synthesis and regulation in purple corn (Zea mays L.) in this study, purple corn 963 was used to compare differences in gene expression during three stages of grain development by transcriptome analysis. A total of 17,168 differentially expressed genes (DEGs) (7564 up-regulated and 9604 down-regulated DGEs) were identified. The DEGs were significantly enriched in "Phenylpropanoid biosynthesis", "Biosynthesis of secondary metabolites", and "Plant hormone signal transduction". In addition, 72 % of the structural genes that regulate anthocyanidin synthesis were up-regulated, and the transcription factors related to the accumulation of anthocyanidins were enriched during grain development. Moreover, the differential expression of phytohormone genes might also be an important factor in anthocyanidin accumulation. Transcriptomic analysis presents a molecular basis for the study of grain color changes in the three stages of grain development, and provides information for further research on the mechanism of anthocyanidin synthesis.

The novel gene BrMYB2, located on chromosome A07, with a short intron 1 controls the purple-head trait of Chinese cabbage (Brassica rapa L.)

Anthocyanins are important secondary metabolites in plants, but information on anthocyanin biosynthesis mechanisms in Chinese cabbage is limited. The new purple head Chinese cabbage cultivar 11S91 was analyzed, and an R2R3-MYB regulatory gene BrMYB2, located on chromosome A07, controlling the dominant purple-head trait was isolated. High expression of BrMYB2 generated a large accumulation of anthocyanins in 11S91, accompanied by highly upregulated BrTT8, BrF3'H, BrDFR1, BrANS1, BrUGTs, BrATs, and BrGSTs. 11S91 inherited the purple locus from purple trait donor 95T2-5, and they shared consensus CDSs and gDNAs with those of BrMYB2 (cBrMYB2 and gBrMYB2). Two SNPs in cBrMYB2 in 11S91 did not cause loss of function; in addition to several SNPs at both ends of intron 1, a large deletion had occurred in intron 1 of gBrMYB2 in 11S91. Genetic transformation of Arabidopsis showed that gBrMYB2 overexpression lines presented deeper purple color and higher expression than did the cBrMYB2 and cBrmyb2 lines, whereas gBrmyb2 with a long intron 1 did not cause the purple phenotype. We first show that BrMYB2 promotes anthocyanin biosynthesis under the control of the short intron 1 of gBrMYB2 in purple head Chinese cabbage, and gBrmyb2 with a long intron 1 represses anthocyanin production in white head Chinese cabbage. This evidence provides a new understanding of anthocyanin biosynthesis and purple germplasm generation in Brassica vegetables.

Transcriptomic profiling of purple broccoli reveals light-induced anthocyanin biosynthetic signaling and structural genes

Purple Broccoli (Brassica oleracea L. var italica) attracts growing attention as a functional food. Its purple coloration is due to high anthocyanin amounts. Light represents a critical parameter affecting anthocyanins biosynthesis. In this study, 'Purple Broccoli', a light-responding pigmentation cultivar, was assessed for exploring the mechanism underlying light-induced anthocyanin biosynthesis by RNA-Seq. Cyanidin, delphinidin and malvidin derivatives were detected in broccoli head samples. Shading assays and RNA-seq analysis identified the flower head as more critical organ compared with leaves. Anthocyanin levels were assessed at 0, 7 and 11 days, respectively, with further valuation by RNA-seq under head-shading and light conditions. RNA sequences were de novo assembled into 50,329 unigenes, of which 38,701 were annotated against four public protein databases. Cluster analysis demonstrated that anthocyanin/phenylpropanoid biosynthesis, photosynthesis, and flavonoid biosynthesis in cluster 8 were the main metabolic pathways regulated by light and had showed associations with flower head growth. A total of 2,400 unigenes showed differential expression between the light and head-shading groups in cluster 8, including 650 co-expressed, 373 specifically expressed under shading conditions and 1,377 specifically expressed under normal light. Digital gene expression (DGE) analysis demonstrated that light perception and the signal transducers CRY3 and HY5 may control anthocyanin accumulation. Following shading, 15 structural genes involved in anthocyanin biosynthesis were downregulated, including PAL, C4H, 4CL, CHS, CHI, F3H and DFR. Moreover, six BoMYB genes (BoMYB6-1, BoMYB6-2, BoMYB6-3, BoMYB6-4, BoMYBL2-1 and BoMYBL2-2) and three BobHLH genes (BoTT8_5-1, BoTT8_5-2 and BoEGL5-3) were critical transcription factors controlling anthocyanin accumulation under light conditions. Based on these data, a light-associated anthocyanin biosynthesis pathway in Broccoli was proposed. This information could help improve broccoli properties, providing novel insights into the molecular mechanisms underpinning light-associated anthocyanin production in purple vegetables.

Pigment variation and transcriptional response of the pigment synthesis pathway in the S2309 triple-color ornamental kale (Brassica oleracea L. var. acephala) line

Ornamental kale is popular because of its colorful leaves and few studies have investigated the mechanism of color changes. In this study, an ornamental kale line (S2309) with three leaf colors was developed. Analysis of the anthocyanin, chlorophyll, and carotenoid contents and RNA-seq were performed on the three leaf color types. There was less chlorophyll in the white leaves and purple leaves than in the green leaves, and the anthocyanin content was greatest in the purple leaves. All the downregulated DEGs related to chlorophyll metabolism were detected only in the S2309_G vs. S2309_W comparison, which indicated that the decrease in chlorophyll content was caused mainly by the inhibition of chlorophyll biosynthesis during the leaf color change from green to white. Moreover, the expression of 19 DEGs involved in the anthocyanin biosynthesis pathway was upregulated. These results provide new insight into the mechanisms underlying the three-color formation.

Grown to be Blue-Antioxidant Properties and Health Effects of Colored Vegetables. Part II: Leafy, Fruit, and Other Vegetables

The current trend for substituting synthetic compounds with natural ones in the design and production of functional and healthy foods has increased the research interest about natural colorants. Although coloring agents from plant origin are already used in the food and beverage industry, the market and consumer demands for novel and diverse food products are increasing and new plant sources are explored. Fresh vegetables are considered a good source of such compounds, especially when considering the great color diversity that exists among the various species or even the cultivars within the same species. In the present review we aim to present the most common species of colored vegetables, focusing on leafy and fruit vegetables, as well as on vegetables where other plant parts are commercially used, with special attention to blue color. The compounds that are responsible for the uncommon colors will be also presented and their beneficial health effects and antioxidant properties will be unraveled.

Abscisic acid and ethylene biosynthesis-related genes are associated with anthocyanin accumulation in purple ornamental cabbage (Brassica oleracea var. acephala)

Purple ornamental cabbage (Brassica oleracea var. acephala) is a popular decorative plant, cultivated for its colorful leaf rosettes that persist in cool weather. It is characterized by green outer leaves and purple inner leaves, whose purple pigmentation is due to the accumulation of anthocyanin pigments. Phytohormones play important roles in anthocyanin biosynthesis in other species. Here, we identified 14 and 19 candidate genes putatively involved in abscisic acid (ABA) and ethylene (ET) biosynthesis, respectively, in B. oleracea. We determined the expression patterns of these candidate genes by reverse-transcription quantitative PCR (RT-qPCR). Among candidate ABA biosynthesis-related genes, the expressions of BoNCED2.1, BoNCED2.2, BoNCED6, BoNCED9.1, and BoAAO3.2 were significantly higher in purple compared to green leaves. Likewise, most of the ET biosynthetic genes (BoACS6, BoACS9.1, BoACS11, BoACO1.1, BoACO1.2, BoACO3.1, BoACO4, and BoACO5) had significantly higher expression in purple compared to green leaves. Among these genes, BoNCED2.1, BoNCED2.2, BoACS11, and BoACO4 showed particularly strong associations with total anthocyanin content of the purple inner leaves. Our results suggest that ABA and ET might promote the intense purple pigmentation of the inner leaves of purple ornamental cabbage.

Molecular analysis of anthocyanin biosynthesis-related genes reveal BoTT8 associated with purple hypocotyl of broccoli (Brassica oleracea var. italica L.)

Broccoli (Brassica oleracea var. italica L.) is a highly nutritious vegetable that typically forms pure green or purple florets. However, green broccoli florets sometimes accumulate slight purplish pigmentation in response environmental factors, decreasing their market value. In the present study, we aimed to develop molecular markers to distinguish broccoli genotypes as pure green or purplish floret color at the early seedling stage. Anthocyanins are known to be involved in the purple pigmentation in plants. The purplish broccoli lines were shown to accumulate purple pigmentation in the hypocotyls of very young seedlings; therefore, the expression profiles of the structural and regulatory genes of anthocyanin biosynthesis were analyzed in the hypocotyls using qRT-PCR. BoPAL, BoDFR, BoMYB114, BoTT8, BoMYC1.1, BoMYC1.2, and BoTTG1 were identified as putative candidate genes responsible for the purple hypocotyl color. BoTT8 was much more highly expressed in the purple than green hypocotyls; therefore, it was cloned and sequenced from various broccoli lines, revealing SNP and InDel variations between these genotypes. We tested four SNPs (G > A; A > T; G > C; T > G) in the first three exons and a 14-bp InDel (ATATTTATATATAT) in the BoTT8 promoter in 51 broccoli genotypes, and we found these genetic variations could distinguish the green lines, purple lines, and F₁ hybrids. These novel molecular markers could be useful in broccoli breeding programs to develop a true green or purple broccoli cultivar.

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

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.

Transcriptome profiling of two contrasting ornamental cabbage (Brassica oleracea var. acephala) lines provides insights into purple and white inner leaf pigmentation

Background

Ornamental cabbage (Brassica oleracea var. acephala) is an attractive landscape plant that remains colorful at low temperatures during winter. Its key feature is its inner leaf coloration, which can include red, pink, lavender, blue, violet and white. Some ornamental cabbages exhibit variation in leaf color pattern linked to leaf developmental stage. However, little is known about the molecular mechanism underlying changes in leaf pigmentation pattern between developmental stages.

Results

The transcriptomes of six ornamental cabbage leaf samples were obtained using Illumina sequencing technology. A total of 339.75 million high-quality clean reads were assembled into 46,744 transcripts and 46,744 unigenes. Furthermore, 12,771 genes differentially expressed across the different lines and stages were identified by pairwise comparison. We identified 74 and 13 unigenes as differentially expressed genes related to the anthocyanin biosynthetic pathway and chlorophyll metabolism, respectively. Among them, three unigenes (BoC4H2, BoUGT9, and BoGST21) and six unigenes (BoHEMA1, BoCRD1, BoPORC1, BoPORC2, BoCAO, and BoCLH1) were found as candidates for the genes encoding enzymes in the anthocyanin biosynthetic pathway and chlorophyll metabolism, respectively. In addition, two unigenes (BoRAX3 and BoTRB1) as MYB candidates, two unigenes (BoMUTE1, and BHLH168-like) as bHLH candidates were identified for purple pigmentation in ornamental cabbage.

Conclusion

Our results indicate that the purple inner leaves of purple ornamental cabbage result from a high level of anthocyanin biosynthesis, a high level of chlorophyll degradation and an extremely low level of chlorophyll biosynthesis, whereas the bicolor (purple/green) outer leaves are due to a moderate level of anthocyanin biosynthesis, a high level of chlorophyll degradation and a very low level of chlorophyll biosynthesis. In white ornamental cabbage, the white inner leaves are due to an extremely low level or absence of anthocyanin biosynthesis, a high level of chlorophyll degradation and a very low level of chlorophyll biosynthesis, whereas the bicolor (white/green) leaves are due to a high level of chlorophyll degradation and a low level of chlorophyll biosynthesis and absence of anthocyanin biosynthesis. These results provide insight into the molecular mechanisms underlying inner and bicolor leaf pigmentation in ornamental cabbage and offer a platform for assessing related ornamental species.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5199-3) contains supplementary material, which is available to authorized users.