Identification of a Strong Anthocyanin Activator, VbMYBA, From Berries of Vaccinium bracteatum Thunb.

Wufanshu (Vaccinium bracteatum Thunb.), which is a wild member of the genus Vaccinium, accumulates high concentration of anthocyanin in its berries. In this study, the accumulated anthocyanins and their derivatives in Wufanshu berries were identified through UHPLC–MS/MS analysis. Candidate anthocyanin biosynthetic genes were identified from the transcriptome of Wufanshu berries. qRT-PCR analyses showed that the expression of anthocyanin structural genes correlated with anthocyanin accumulation in berries. The R2R3-MYB, VbMYBA, which is a homolog of anthocyanin promoting R2R3-MYBs from other Vaccinium species, was also identified. Transient expression of VbMYBA in Nicotiana tabacum leaves confirmed its role as an anthocyanin regulator, and produced a higher anthocyanin concentration when compared with blueberry VcMYBA expression. Dual-luciferase assays further showed that VbMYBA can activate the DFR and UFGT promoters from other Vaccinium species. VbMYBA has an additional 23 aa at the N terminus compared with blueberry VcMYBA, but this was shown not to affect the ability to regulate anthocyanins. Taken together, our results provide important information on the molecular mechanisms responsible for the high anthocyanin content in Wufanshu berries.

Whole-Genome Identification and Comparative Expression Analysis of Anthocyanin Biosynthetic Genes in Brassica napus

Anthocyanins contribute to most colors of plants and play protective roles in response to abiotic stresses. Brassica napus is widely cultivated worldwide as both an oilseed and a vegetable. However, only several high anthocyanin-containing cultivars have been reported, and the mechanisms of anthocyanin accumulation have not been well-elucidated in B. napus. Here, the phenotype, comparative whole-genome identification, and gene expression analysis were performed to investigate the dynamic change of the anthocyanin content and the gene expression patterns of anthocyanin biosynthetic genes (ABGs) in B. napus. A total of 152 ABGs were identified in the B. napus reference genome. To screen out the critical genes involved in anthocyanin biosynthesis and accumulation, the RNA-seq of young leaves of two B. napus lines with purple leaves (PL) or green leaves (GL), and their F1 progeny at 41, 91, and 101 days were performed to identify the differentially expressed genes. The comparative expression analysis of these ABGs indicated that the upregulation of TT8 together with its target genes (such as DFR, ANS, UFGT, and TT19) might promote the anthocyanin accumulation in PL at the early developmental stage (41–91 days). While the downregulation of those ABGs and anthocyanin degradation at the late developmental stage (91–101 days) might result in the decrease in anthocyanin accumulation. Our results would enhance the understanding of the regulatory network of anthocyanin dynamic accumulation in B. napus.

Integrated Analysis of the Metabolome and Transcriptome on Anthocyanin Biosynthesis in Four Developmental Stages of Cerasus humilis Peel Coloration

Cerasus humilis is a unique dwarf shrub and fruit color is an important trait in the species. In this study, we evaluated the transcriptomic and metabolomic profiles of the plant at different developmental stages to elucidate the mechanism underlying color formation. In a metabolomics analysis, 16 anthocyanin components were identified at four developmental stages, and high levels of cyanidin O-syringic acid and pelargonidin 3-O-beta-d-glucoside (callitephin chloride) were correlated with the reddening of the fruit peel. A co-expression analysis revealed that ANS and UFGT play key roles in pigmentation (PCC > 0.82). Additionally, transcriptome data showed that most anthocyanin biosynthetic genes and two MYB transcription factors were significantly up-regulated. QRT-PCR results for these differentially expressed genes were generally consistent with the high-throughput sequencing. Moreover, the overexpression of ChMYB1 (TRINITY_DN21536_c0_g1) in apple calli could contribute to the accumulation of anthocyanin. It was also found that UFGT (TRINITY_DN19893_c1_g5) and ChMYB1 (TRINITY_DN21536_c0_g1) have similar expression patterns. These findings provide insight into the mechanisms underlying anthocyanin accumulation and coloration during fruit peel development, providing a basis for the breeding of anthocyanin-rich C. humilis cultivars.

Anthocyanin Accumulation and Related Gene Expression Profile in ‘Red Zaosu’ Pear and Its Green Mutant

Red-skinned pear is a promising commercial fruit due to its attractive appearance and nutritious value. Anthocyanin is the determinant of the red coloration of the pear peel. However, differences in anthocyanin accumulation exist among red pear cultivars with different genetic backgrounds. In this study, we analyzed the anthocyanin content and gene expression patterns in the fruits and different tissues of the red pear ‘Red Zaosu’ at different developmental stages and found a difference in anthocyanin accumulation between ‘Red Zaosu’ pear and its green mutant. The data showed that the expression profiles of transcripts that encoded critical anthocyanin biosynthetic genes were basically consistent with a tendency to a decreased anthocyanin content during fruit development, indicating that a synergistic effect of these genes was responsible for anthocyanin biosynthesis and regulation. Tissue-specific expression analysis of anthocyanin biosynthetic genes showed that they could be expressed in all tissues but at different levels. PbF3H, PbDFR, and PbANS were mainly expressed during the early flowering period, which explained the reduced levels of anthocyanin content in petals. Additionally, the content of anthocyanins and the expression levels of PbDFR, PbANS, and PbMYB10 significantly decreased in the green mutant of ‘Red Zaosu’, suggesting that PbDFR, PbANS, and PbMYB10 probably play a decisive role in determining the skin coloration of ‘Red Zaosu’ and its green mutant.

Activation of PsMYB10.2 Transcription Causes Anthocyanin Accumulation in Flesh of the Red-Fleshed Mutant of ‘Sanyueli’ (Prunus salicina Lindl.)

Plum is one of the most important stone fruits in the world and anthocyanin-rich plums are increasingly popular due to their health-promoting potential. In this study, we investigated the mechanisms of anthocyanin accumulation in the flesh of the red-fleshed mutant of the yellow-fleshed plum ‘Sanyueli’. RNA-Seq and qRT-PCR showed that anthocyanin biosynthetic genes and the transcription factor PsMYB10.2 were upregulated in the flesh of the mutant. Functional testing in tobacco leaves indicated that PsMYB10.2 was an anthocyanin pathway activator and can activate the promoter of the anthocyanin biosynthetic genes PsUFGT and PsGST. The role of PsMYB10.2 in anthocyanin accumulation in the flesh of plum was further confirmed by virus-induced gene silencing. These results provide information for further elucidating the underlying mechanisms of anthocyanin accumulation in the flesh of plum and for the breeding of new red-fleshed plum cultivars.

Comparative transcriptome analysis reveals key genes associated with pigmentation in radish (Raphanus sativus L.) skin and flesh

Radish (Raphanus sativus) is an important vegetable worldwide that exhibits different flesh and skin colors. The anthocyanins responsible for the red and purple coloring in radishes possess nutritional value and pharmaceutical potential. To explore the structural and regulatory networks related to anthocyanin biosynthesis and identify key genes, we performed comparative transcriptome analyses of the skin and flesh of six colored radish accessions. The transcript profiles showed that each accession had a species-specific transcript profile. For radish pigmentation accumulation, the expression levels of anthocyanin biosynthetic genes (RsTT4, RsC4H, RsTT7, RsCCOAMT, RsDFR, and RsLDOX) were significantly upregulated in the red- and purple-colored accessions, but were downregulated or absent in the white and black accessions. The correlation test, combined with metabolome (PCC > 0.95), revealed five structural genes (RsTT4, RsDFR, RsCCOAMT, RsF3H, and RsBG8L) and three transcription factors (RsTT8-1, RsTT8-2, and RsPAR1) to be significantly correlated with flavonoids in the skin of the taproot. Four structural genes (RsBG8L, RsDFR, RsCCOAMT, and RsLDOX) and nine transcription factors (RsTT8-1, RsTT8-2, RsMYB24L, RsbHLH57, RsPAR2L, RsbHLH113L, RsOGR3L, RsMYB24, and RsMYB34L) were found to be significantly correlated with metabolites in the flesh of the taproot. This study provides a foundation for future studies on the gene functions and genetic diversity of radish pigmentation and should aid in the cultivation of new valuable radish varieties.

DNA methylation balance is involved in anthocyanin accumulation during Vaccinium corymbosum fruit ripening

BACKGROUND: DNA methylation balance is an important regulatory mechanism for mammalian and plant development. The fruit ripening and anthocyanin accumulation of Vaccinium corymbosum are complex developmental processes that involve numerous physiological, biochemical, and structural alterations. OBJECTIVE: This study aimed to investigate the correlation of DNA methylation balance, DNA methylation and demethylation-related gene expression models and anthocyanin accumulation during blueberry fruit ripening. METHODS: The anthocyanin contents during V. corymbosum ‘O’Neal’ fruit development were evaluated. The V. corymbosum DNA methylation- and anthocyanin accumulation-related genes were isolated, and their relative expression patterns were detected during flower bud enlargement and fruit development. Moreover, the relative expression patterns of anthocyanin biosynthetic genes and the dynamic changes in the DNA methylation of the promoter sequences of key anthocyanin biosynthetic genes were evaluated. RESULTS: The results showed that the DNA methylation level of V. corymbosum fruit was consistent with anthocyanin accumulation during ripening, and the expression levels of anthocyanin biosynthetic and DNA methylation-related genes. CONCLUSIONS: During V. corymbosum fruit ripening, anthocyanin accumulation is regulated partially by DNA methylation balance of VcCHS and VcANS promoters.