Abstract
The MBW complex consisting of the three proteins R2R3MYB, bHLH and WDR regulates five traits in Arabidopsis thaliana including trichome and root hair patterning, seed coat color, anthocyanidin production and seed coat mucilage release. The WDR gene TTG1 regulates each trait in specific combinations with different bHLH and R2R3MYB proteins. In this study we analyze to what extent the biochemical properties of the MBW proteins contribute to trait specificity by expressing them in appropriate A. thaliana mutants. We show that the rescue behavior of A. thaliana bHLH and R2R3MYB protein is sufficient to explain the function as derived previously from mutant analysis. When extending this rescue approach using MBW proteins from other species we find that proteins involved in anthocyanidin regulation typically show a rescue of the anthocyanidin phenotype but not of the other traits. Finally, we correlate the rescue abilities of MBW protein from different species with the A. thaliana proteins.
Highlights
In the model plant Arabidopsis thaliana five traits including trichome and root hair patterning, seed coat color, anthocyanidin production and seed coat mucilage release are genetically linked through the action of the TRANSPARENT TESTA GLABRA1 (TTG1) gene (Koornneef, 1981)
Rescue With Arabidopsis MBW Proteins Reveals Trait-Specific Protein Properties In Arabidopsis, the MBW complex regulates five different traits by involving different basic Helix-Loop-Helix factors (bHLH) and R2R3MYBs in a trait-specific manner. This raises the question, whether trait specificity is due to transcriptional regulation or different properties of bHLH and R2R3MYB proteins
Rescue experiments with A. thaliana bHLH proteins GL3, EGL3, and TT8 revealed that the rescue ability of the different traits matches their genetic requirements (Supplementary Table S1) (Zhang et al, 2003)
Summary
In the model plant Arabidopsis thaliana five traits including trichome and root hair patterning, seed coat color, anthocyanidin production and seed coat mucilage release are genetically linked through the action of the TRANSPARENT TESTA GLABRA1 (TTG1) gene (Koornneef, 1981). TTG1 encodes a WDR protein (Walker et al, 1999) that forms protein complexes with R2R3MYB and basic Helix-Loop-Helix factors (bHLH) that transcriptionally regulate downstream target genes (for review see Lloyd et al, 2017). This complex is called the MBW complex (Ramsay and Glover, 2005; Xu et al, 2015; Zhang and Schrader, 2017) and it forms through the binding of TTG1 and the MYB protein to the bHLH protein (Payne et al, 2000; Zhang et al, 2003; Zimmermann et al, 2004; Feller et al, 2006).
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