MBW complexes impinge on anthocyanidin reductase gene regulation for proanthocyanidin biosynthesis in persimmon fruit

Francisco Gil-Muñoz,Cristina Besada,María del Mar Naval,Alejandra Salvador,Jesús A. Sánchez-Navarro,María Luisa Badenes,Gabino Ríos

doi:10.1038/s41598-020-60635-w

Francisco Gil-Muñoz, Cristina Besada + Show 5 more

Open Access

https://doi.org/10.1038/s41598-020-60635-w

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Abstract

MBW protein complexes containing MYB, bHLH and WD40 repeat factors are known transcriptional regulators of secondary metabolites production such as proanthocyanidins and anthocyanins, and developmental processes such as trichome formation in many plant species. DkMYB2 and DkMYB4 (MYB-type), DkMYC1 (bHLH-type) and DkWDR1 (WD40-type) factors have been proposed by different authors to take part of persimmon MBW complexes for proanthocyanidin accumulation in immature fruit, leading to its characteristic astringent flavour with important agronomical and ecological effects. We have confirmed the nuclear localization of these proteins and their mutual physical interaction by bimolecular fluorescence complementation analysis. In addition, transient expression of DkMYB2, DkMYB4 and DkMYC1 cooperatively increase the expression of a persimmon anthocyanidin reductase gene (ANR), involved in the biosynthesis of cis-flavan-3-ols, the structural units of proanthocyanidin compounds. Collectively, these data support the presence of MBW complexes in persimmon fruit and suggest their coordinated participation in ANR regulation for proanthocyanidin production.

Highlights

MBW protein complexes containing MYB, basic helix-loop-helix (bHLH) and WD40 repeat factors are known transcriptional regulators of secondary metabolites production such as proanthocyanidins and anthocyanins, and developmental processes such as trichome formation in many plant species
The subcellular localization of these four putative MBW components in persimmon has been elucidated by transient expression in Nicotiana benthamiana leaves of the four corresponding genes fused to enhanced green fluorescent protein gene
DkMYB2, DkMYB4, DkMYC1 and DkWDR1 have been postulated to co-regulate the expression of PA biosynthesis genes in persimmon as a complex[26], and a coordinated nuclear co-localization of them is expected

Summary

Introduction

MBW protein complexes containing MYB, bHLH and WD40 repeat factors are known transcriptional regulators of secondary metabolites production such as proanthocyanidins and anthocyanins, and developmental processes such as trichome formation in many plant species. Transient expression of DkMYB2, DkMYB4 and DkMYC1 cooperatively increase the expression of a persimmon anthocyanidin reductase gene (ANR), involved in the biosynthesis of cis-flavan-3-ols, the structural units of proanthocyanidin compounds These data support the presence of MBW complexes in persimmon fruit and suggest their coordinated participation in ANR regulation for proanthocyanidin production. In Arabidopsis, regulation of the ANR orthologous gene BANYULS (BAN) and PA accumulation in seed coat requires the concerted action of TRANSPARENT TESTA2 (TT2), TRANSPARENT TESTA8 (TT8) and TRANSPARENT TESTA GLABRA1 (TTG1), encoding respectively a R2R3-MYB transcription factor, a basic helix-loop-helix (bHLH) transcription factor and a WD40-repeat (WDR) protein[20] These regulatory factors form a ternary complex named MYB-bHLH-WD40 (MBW) that may invoke the participation of alternative MYB and bHLH components for the regulation of particular steps of PA and anthocyanin biosynthetic pathways[21,22]. We go further on the cytological and molecular characterization of MBW complex in persimmon by approaching the subcellular localization, protein interaction and transcriptional regulation effects of these MYB (DkMYB2 and DkMYB4), bHLH (DkMYC1) and WD40 (DkWDR1) components

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