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

Abstract

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.

Validation of reference genes for gene expression analysis in fruit development of Vaccinium bracteatum Thunb. using quantitative real-time PCR

“…Recently, the species was demonstrated to confer prominent benefits for hypoglaemia, sedation and hypnosis, antineoplastic, antimicrobial and antioxidant activity 3 – 9 . Additionally, VBT contains high levels of nutrients, such as amino acids, minerals and unsaturated fatty acids 3 , 5 , 10 . Therefore, VBT is an important resource for the traditional diet as well as for its pharmacological effects, for which it has considerable prospects for development.…”

UV-B induces the expression of flavonoid biosynthetic pathways in blueberry (Vaccinium corymbosum) calli

“…Among the encoded transcription factors, VcMYBPA1 and MYBPA2.1 (subgroup 5), MYB114 and MYBA2 (subgroup 6), and MYBF (subgroup 7) promoted the expression of genes involved in flavonoid biosynthesis. Subgroups 5, 6, and 7 positively regulate anthocyanin, proanthocyanidin, or flavonol biosynthesis ( Bogs et al., 2007 ; Czemmel et al., 2009 ; Zifkin et al., 2012 ; An et al., 2015 ; Plunkett et al., 2018 ; Karppinen et al., 2021 ; Zhang et al., 2021 ). Thus, these MYBs may activate UV-B-induced flavonoid biosynthesis.…”

“…Among these regulators, four subgroups (4, 5, 6, and 7) from the 22 existing R2R3-MYB transcription factor gene family subgroups play regulatory roles in the biosynthesis of flavonoid compounds. More specifically, subgroup 4 encodes suppressors of flavonoid biosynthesis, while subgroups 5, 6, and 7 encode positive regulators of flavonoid biosynthesis ( Kranz et al., 1998 ; Plunkett et al., 2018 ; Zhang et al., 2021 ). For example, the subgroup 4 FaMYB1 from strawberry ( Fragaria ananassa ) suppressed anthocyanin and flavonol accumulation and VvMYBC2-L1 from grapevine ( Vitis vinifera ) suppressed proanthocyanidin biosynthesis ( Aharoni et al., 2001 ; Cavallini et al., 2015 ).…”

MYB pathways that regulate UV-B-induced anthocyanin biosynthesis in blueberry (Vaccinium corymbosum)

“…In the R2R3-MYB gene family, subgroup 6 members promote anthocyanin biosynthesis and subgroup 4 members inhibit anthocyanin biosynthesis. For example, in the Vaccinium genus, VbMYBA , VmMYBA1 , VmMYBA2 , and VcMYBA , which belong to subgroup 6, activate anthocyanin biosynthesis, and, in strawberry ( Fragaria × ananassa ), FaMYB1 , a member of subgroup 4, suppresses anthocyanin accumulation ( Aharoni et al., 2001 ; Plunkett et al., 2018 ; Karppinen et al., 2021 ; Zhang et al., 2021 ). UV-B also affects the expression of MYB transcription factor genes from subgroups 4 and 6.…”