Identification and characterization of regulatory network components for anthocyanin synthesis in barley aleurone

Abstract

BackgroundAmong natural populations, there are different colours of barley (Hordeum vulgare L.). The colour of barley grains is directly related to the accumulation of different pigments in the aleurone layer, pericarp and lemma. Blue grain colour is due to the accumulation of anthocyanins in the aleurone layer, which is dependent on the presence of five Blx genes that are not sequenced yet (Blx1, Blx3 and Blx4 genes clustering on chromosome 4HL and Blx2 and Blx5 on 7HL). Due to the health benefits of anthocyanins, blue-grained barley can be considered as a source of dietary food. The goal of the current study was to identify and characterize components of the anthocyanin synthesis regulatory network for the aleurone layer in barley.ResultsThe candidate genes for components of the regulatory complex MBW (consisting of transcription factors MYB, bHLH/MYC and WD40) for anthocyanin synthesis in barley aleurone were identified. These genes were designated HvMyc2 (4HL), HvMpc2 (4HL), and HvWD40 (6HL). HvMyc2 was expressed in aleurone cells only. A loss-of-function (frame shift) mutation in HvMyc2 of non-coloured compared to blue-grained barley was revealed. Unlike aleurone-specific HvMyc2, the HvMpc2 gene was expressed in different tissues; however, its activity was not detected in non-coloured aleurone in contrast to a coloured aleurone, and allele-specific mutations in its promoter region were found. The single-copy gene HvWD40, which encodes the required component of the regulatory MBW complex, was expressed constantly in coloured and non-coloured tissues and had no allelic differences. HvMyc2 and HvMpc2 were genetically mapped using allele-specific developed CAPS markers developed. HvMyc2 was mapped in position between SSR loci XGBS0875-4H (3.4 cM distal) and XGBM1048-4H (3.4 cM proximal) matching the region chromosome 4HL where the Blx-cluster was found. In this position, one of the anthocyanin biosynthesis structural genes (HvF3’5’H) was also mapped using an allele-specific CAPS-marker developed in the current study.ConclusionsThe genes involved in anthocyanin synthesis in the barley aleurone layer were identified and characterized, including components of the regulatory complex MBW, from which the MYC-encoding gene (HvMyc2) appeared to be the main factor underlying variation of barley by aleurone colour.Electronic supplementary materialThe online version of this article (10.1186/s12870-017-1122-3) contains supplementary material, which is available to authorized users.

Genes Determining the Synthesis of Lavonoid and Melanin Pigments in Barley

“…Четыре копии гена F3′5′h были выявлены в геноме ячменя на основе известных последовательностей F3′5′h двудольных видов растений (Strygina et al, 2017;Вихорев и др., 2018). Одна копия была картирована в хромосоме 4HL (F3′5′h-1), две -в хромосоме 6H (F3′5′h-2 и F3′5′h-3) и одна в хромосоме 7H (F3′5′h-4).…”

“…Одна копия была картирована в хромосоме 4HL (F3′5′h-1), две -в хромосоме 6H (F3′5′h-2 и F3′5′h-3) и одна в хромосоме 7H (F3′5′h-4). Для копии F3′5′h-1 по-казана тканеспецифическая экспрессия в алейроновом слое зерновки окрашенных и неокрашенных линий ячменя (Strygina et al, 2017). Для F3′5′h-4 была продемонстри-рована активность во всех проанализированных слоях зерновки ячменя, а также в стеблях, контрастных по со-держанию антоциановых пигментов (Вихорев и др., 2018).…”

“…рис. 2), который был выделен позже (Strygina et al, 2017). В дополнение к выявленным новым локусам R.A. Finch и E. Simpson (1978) показали, что существует рецессивная энхансерная последовательность en-Bl (enhancer of blue and pink aleurone color, ibl) с неизвестным местоположением, при наличии которой происходит усиление интенсивности голубой или розовой окраски.…”

“…В исследовании (Strygina et al, 2017) аннотированы гены, кодирующие ТФ MYC, MYB и WD40, регулирующие биосинтез антоцианов в алейроне. Эти гены были обозначены: HvMyc2 (4HL), HvMpc2 (4HL) и HvWD40 (6HL).…”

“…HvMyc2 вместе с HvF3′5′h (см. выше) были точно картированы в позиции кластера Blx в длинном плече хромосомы 4H (Matthews et al, 2003;Strygina et al, 2017), тем самым они стали кандидатами для двух из трех тесно сцепленных генов Blx.…”