Regulation of the Flavonoid Biosynthesis Pathway Genes in Purple and Black Grains of Hordeum vulgare

Abstract

Barley grain at maturity can have yellow, purple, blue, and black pigmentations which are suggested to play a protective role under stress conditions. The first three types of the colors are caused by phenolic compounds flavonoids; the last one is caused by phytomelanins, oxidized and polymerized phenolic compounds. Although the genetic basis of the flavonoid biosynthesis pathway in barley has been thoroughly studied, there is no data yet on its regulation in purple and black barley grains. In the current study, genetic model of Hordeum vulgare ‘Bowman’ near-isogenic lines (NILs) was used to investigate the regulation of the flavonoid biosynthesis in white, purple, and black barley grains. Microsatellite genotyping revealed donor segments in the purple- and black-grained lines on chromosomes 2H (in region of the Ant2 gene determining purple color of grains) and 1H (in region of the Blp gene determining black lemma and pericarp), respectively. The isolated dominant Ant2 allele of the purple-grained line has high level of sequence similarity with the recessive Bowman’s ant2 in coding region, whereas an insertion of 179 bp was detected in promoter region of ant2. This structural divergence between Ant2 and ant2 alleles may underlie their different expression in grain pericarp: Bowman’s Ant2 is not transcribed, whereas it was up-regulated in the purple-grained line with coordinately co-expressed flavonoid biosynthesis structural genes (Chs, Chi, F3h, F3’h, Dfr, Ans). This led to total anthocyain content increase in purple-grained line identified by ultra-performance liquid chromatography (HPLC). Collectively, these results proved the regulatory function of the Ant2 gene in anthocyanin biosynthesis in barley grain pericarp. In the black-grained line, the specific transcriptional regulation of the flavonoid biosynthesis pathway genes was not detected, suggesting that flavonoid pigments are not involved in development of black lemma and pericarp trait.

Whole genome sequencing and comparative genomic analysis reveal novel allelic variations unique to a purple colored rice landrace (Oryza sativa ssp. indica cv. Purpleputtu)

“…It is well known that betanidin degradation is a prerequisite step in eliminating betacyanin production in plants. It is worth noting that most flowering plants do not accumulate betacyanins and thus these two different color pigments are mutually exclusive (Rodriguez-Amaya, 2018; Shoeva et al , 2016, Khoo et al , 2017). Sucrose degradation is a prerequisite for preventing root hypoxia and salinity tolerance in some plants.…”

Comparative characteristic of near-isogenic lines differing by the Blp locus in respect to abiotic stress resistance

“…nordgen.org) and previously genotyped by microsatellite markers. The only chromosome segment in 1HL was different in the lines (Druka et al 2011;Shoeva et al, 2016).…”

Molecular Mechanism of Functional Ingredients in Barley to Combat Human Chronic Diseases

“…Total polyphenols (291.7 mg/100 g) and proanthocyanidins (163.0 [43]. Pigmentations play a protective role under stress conditions, which are caused by flavonoids (yellow, purple, and blue) of Ant2 gene in anthocyanin biosynthesis in barley grain pericarp, meanwhile Ant1 associated with gene encoding an R2R3 myeloblastosis transcription factor [44], but black is caused by phytomelanins and oxidized as well as polymerized phenolic compounds [45]. There are larger variation on free (20.61~25.59 mg/100 g), bound (14.91~22.38 mg/100 g), and total flavones (37.91~47.98 mg/100 g) in 12 blue hulless barley grains [39].…”