The control of red colour by a family of MYB transcription factors in octoploid strawberry (Fragaria × ananassa) fruits

Abstract

Summary Octoploid strawberry (Fragaria × ananassa Duch.) is a model plant for research and one of the most important non‐climacteric fruit crops throughout the world. The associations between regulatory networks and metabolite composition were explored for one of the most critical agricultural properties in octoploid strawberry, fruit colour. Differences in the levels of flavonoids are due to the differences in the expression of structural and regulatory genes involved in flavonoid biosynthesis. The molecular mechanisms underlying differences in fruit colour were compared between red and white octoploid strawberry varieties. FaMYB genes had combinatorial effects in determining the red colour of fruit through the regulation of flavonoid biosynthesis in response to the increase in endogenous ABA at the final stage of fruit development. Analysis of alleles of FaMYB10 and FaMYB1 in red and white strawberry varieties led to the discovery of a white‐specific variant allele of FaMYB10, FaMYB10‐2. Its coding sequence possessed an ACTTATAC insertion in the genomic region encoding the C‐terminus of the protein. This insertion introduced a predicted premature termination codon, which suggested the loss of intact FaMYB10 protein playing a critical role in the loss of red colour in white octoploid strawberry.

Allelic Variation ofMYB10is the Major Force Controlling Natural Variation of Skin and Flesh Color in Strawberry (Fragariaspp.) fruit

“…An independent missense mutation, famyb10-1, was also found in this study for lines with white skin color from UF breeding population 17.66. The mutation is same as a previously identified INDEL (Wang et al, 2020). Our study precisely located this mutation to the dominant homoeologous allele on Fvb1-2 and showed that it controls fruit skin color.…”

“…Deletion of the 54 C-terminal residues may render FaMYB10 inactive. In fact, this same polymorphism was recently shown to be associated with white fruits in 'Snow Princess', and restoration of anthocyanin biosynthesis was only possible by over-expression of WT MYB10 (Wang et al, 2020). The presence of the same mutation, hereafter named famyb10-1, suggests that the white-fruited selection FL 14.29-1 and 'Snow Princess' may share a common pedigree.…”

“…Effects in the same direction on quercetin derivatives and coumaric acid derivatives were observed when FaMYB10 was transiently down-regulated in octoploid strawberry (Medina-Puche et al, 2014) or when FvMYB10 was engineered in F. vesca (Lin-Wang et al, 2014). Other studies have compared secondary metabolites of fruit from cultivars differing in fruit color and again quercetin derivatives, coumaric and cinnamic hexoses and ellagic acid were also associated with MYB10 function (Härtl et al, 2017;Wang et al, 2020). These results show that a very limited number of metabolites are affected by MYB10 regulation, suggesting a primary influence on anthocyanin biosynthesis and few effects in specific flavonols, ellagitanins and hydroxycinnamic acids.…”

“…Each of these three studies have identified three to six genomic regions contributing to color-related traits, but the phenotypic variation explained by each QTL was relatively low, with only few QTLs explaining more than 15% of phenotypic variation. More recently, an 8bp insertion in the coding region of FaMYB10 has been associated with loss of anthocyanins in fruits of 'Snow Princess', an octoploid strawberry cultivar with completely white fruits (Wang et al, 2020), but its subgenome location was not described. Three full-length homoeologous FaMYB10 genes were annotated in the octoploid 'Camarosa' genome (Edger et al, 2019a).…”

The genetic architecture of fruit colour in strawberry (Fragaria × ananassa) uncovers the predominant contribution of theF. vescasubgenome to anthocyanins and reveals underlying genetic variations

“…To date, various MYB transcription factors and the MYB/bHLH/WD-repeat protein complex are known to regulate anthocyanin biosynthesis in strawberry (Salvatierra et al 2013; Schaart et al, 2013; Medina-Puche et al 2014; Wang et al 2020). The best studied strawberry MYB is MYB10, whose mutation induces a loss of red fruit colour in the cultivated strawberry and in the wild diploid species F. vesca and F. nilgirensis (Medina-Puche et al 2014; Hawkins et al 2016; Wang et al 2020; Castillejo et al 2020; Zhang et al 2020). However, the most likely MYB candidate gene underlying the female F3a pelargonidin-3-glucoside mQTL is not homologous to a well characterized strawberry MYB.…”