Anthocyanin leaf markings are regulated by a family of R2R3‐MYB genes in the genus Trifolium

Abstract

SummaryAnthocyanin pigments accumulate to form spatially restricted patterns in plants, particularly in flowers, but also occur in vegetative tissues. Spatially restricted anthocyanin leaf markings are poorly characterised in plants, but are common in forage legumes.We hypothesised that the molecular basis for anthocyanin leaf markings in Trifolium spp. is due to the activity of a family of R2R3-MYB genes.R2R3-MYB genes were identified that are associated with the two classic pigmentation loci in T. repens. The R locus patterns 'red leaf', 'red midrib' and 'red fleck' are conditioned by a single MYB gene, RED LEAF. The 'diffuse red leaf' trait is regulated by the RED LEAF DIFFUSE MYB gene. The V locus was identified through mapping two V-linked traits, 'V-broken yellow' (Vby) and 'red leaflet' (Vrl ). Two highly similar R2R3-MYB genes, RED V-a and RED Vb, mapped to the V locus and co-segregated with the RED V pigmentation pattern. Functional characterisation of RED LEAF and RED V was performed, confirming their function as anthocyanin regulators and identifying a C-terminal region necessary for transactivation.The mechanisms responsible for generating anthocyanin leaf markings in T. repens provide a valuable system to compare with mechanisms that regulate complex floral pigmentation.

The R2R3-MYB TT2b and the bHLH TT8 genes are the major regulators of proanthocyanidin biosynthesis in the leaves of Lotus species

“…The MBW complex operates within a gene regulation network that involves reinforcement and repression (Xu et al 2015). Current models in T. repens suggest that the MBW complexes that control anthocyanins and proantochyanidins activate the expression of the bHLH clade to which TT8 belongs (Albert et al 2014;Albert 2015). Our transcriptomic data can therefore be interpreted to signify that the Lotus MBW complex formed primarily, but not exclusively, by TT2b as the R2R3-MYB partner, activates the transcription of TT8 in a self-reinforcement mechanism.…”

Metabolic engineering of proanthocyanidin production by repressing the isoflavone pathways and redirecting anthocyanidin precursor flux in legume

“…The previous study has shown that MtPAR alone could not bind to the promoter of ANR gene; but it directly binds to MtWD40‐1 promoter and regulates a subset of PA biosynthetic genes (Verdier et al ., ). However, overexpression of MtWD40‐1 alone failed to increase PA production, although MBW transcription factors are indispensible in regulating PA biosynthesis (Lepiniec et al ., ; Pang et al ., ; Xu et al ., , ; Albert et al ., ). Here, we proved that MtPAR interacts with MtTT8, MtWD40‐1 to form a MtPAR‐MtWD40‐1‐MtTT8 MBW complex, which can trans ‐activate the promoter of ANR and activating PA biosynthesis (Figure a–f).…”

Overexpression of SbMyb60 impacts phenylpropanoid biosynthesis and alters secondary cell wall composition in Sorghum bicolor

“…poplar and Arabidopsis) comparatively little is known about its regulation in monocots, such as sorghum, which is rapidly emerging as a biofeedstock and can be grown in drought‐prone areas. The MYB TFs are one of the major regulators of phenylpropanoid biosynthesis, and specific MYB proteins have been shown to induce the biosynthesis of various monolignols (Zhong and Ye, ; Zhou et al ., ), flavonoids (Grotewold et al ., ; Moyano et al ., ), anthocyanins (Albert et al ., ; Ibraheem et al ., ) and other aromatic compounds (Borevitz, ). In this study, the function of the SbMyb60 TF was investigated in planta in the emerging bioenergy grass sorghum.…”