VaSDC1 Is Involved in Modulation of Flavonoid Metabolic Pathways in Black and Red Seed Coats in Adzuki Bean (Vigna angularis L.)

Abstract

Seed coat colour is an important nutritional quality trait. Variations in anthocyanins and flavonoids induce the diversity of seed coat colour in adzuki bean (Vigna angularis L.). Red seed coat and black seed coat are important adzuki bean cultivars. Insights into the differences of flavonoid metabolic pathways between black and red adzuki bean are significant. In this study, we explored that the difference in seed coat colour between the red (Jingnong6) and the black (AG118) is caused by the accumulation of anthocyanins. The RNA-sequencing (RNA-Seq) and real-time reverse transcription (qRT)-PCR results showed that the Vigna angularis L. seed coat color (VaSDC1) gene, an R2R3-MYB transcription factor, should be the key gene to regulate the black and red seed coat colours. In three different colouring staes of seed development, VaSDC1 was specifically expressed in the black seed coat (AG118) landrace, which activates the structural genes of flavonoid metabolic pathways. As a result, this caused a substantial accumulation of anthocyanins and created a dark blue-black colour. In the red (Jingnong6) seed coat variety, low expression levels of VaSDC1 resulted in a lower accumulation of anthocyanins than in AG118. In addition, VaSDC1 was genetically mapped in the interval between simple-sequence repeat (SSR) markers Sca326-12, Sca326-4, and BAgs007 on chromosome 3 using an F4 segregating population derived from the cross between Jingnong6 and AG118. These results will facilitate the improvement of nutritional quality breeding in adzuki beans.

Variability of Anthocyanin Concentrations, Total Metabolite Contents and Antioxidant Activities in Adzuki Bean Cultivars

“…Pt-3- O -Ga was not detected in Geomguseul ( Figure 2 a,b). As outlined by Li et al [ 37 ] and Chu et al [ 41 ], such differences in the distribution of anthocyanins between colored adzuki beans could be due to the variation in the gene composition and enzymes responsible for anthocyanin biosynthesis. In terms of concentration, the dominance of D-3- O -G was observed in both Chilbopat (10.88 mg/g) and Geomguseul (12.46 mg/g) followed by D-3- O -Ga (3.97 and 5.30 mg/g, respectively) and D-3,5- O -di-G (3.89 and 5.21 mg/g, respectively) ( p < 0.05).…”

Progress in Adzuki Bean Seed Coat Colour Studies

“…This gene is identified as a R2R3-MYB transcription factor, which displays the highest homology with AtMYB75 influencing the colour of Arabidopsis thaliana . During the three different colouring stages of seed development, VaSDC1 was specifically expressed in the black seed coat, which may activate structural genes in flavonoid metabolism and cause the differences between black AG118 and red Jingnong6 [ 35 ]. Together, the above finding first reveals the molecular mechanism in which a single genetic locus regulates the difference between two seed coat colours in adzuki bean.…”

Regulation of flavonoid biosynthesis in representatives of the tribe Phaseoleae DC.

“…Таким образом, из набора дифференциально экспрессирующихся генов, идентифицированных по результатам транскриптомного анализа V. unguiculata, были аннотированы некоторые гены-кандидаты, вовлеченные в регуляцию биосинтеза флавоноидов, но при этом не установлены тканеспецифичные закономерности их экспрессии. В настоящее время активно ведутся работы по изучению системы генов биосинтеза флавоноидных пигментов у адзуки V. angularis (Chu et al, 2021a;2021b). На хромосоме 3 был выделен ген VaSDC1, кодирующий белок семейства R2R3-Myb, предположительно определяющий красную или черную окраску семян адзуки.…”