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

Abstract

Anthocyanins are the principal color-producing compounds synthesized in developing fruits of strawberry (Fragaria spp.). Substantial natural variation in color have been observed in fruits of diploid and octoploid accessions, resulting from distinct accumulation and distribution of anthocyanins in fruits. Anthocyanin biosynthesis is controlled by a clade of R2R3 MYB transcription factors, among which MYB10 has been shown as the main activator in strawberry fruit. Here, we show that MYB10 mutations cause most of the anthocyanin variation observed in diploid woodland strawberry (F. vesca) and octoploid cultivated strawberry (F. ×ananassa). Using a mapping-by-sequencing approach, we identified a gypsytransposon insertion in MYB10 that truncates the protein and knocks out anthocyanin biosynthesis in a white-fruited F. vesca ecotype. Two additional lossof-function MYB10 mutations were identified among geographically diverse whitefruited F. vesca ecotypes. Genetic and transcriptomic analyses in octoploid Fragaria spp. revealed that FaMYB10-2, one of three MYB10 homoeologs identified, residing in the F. iinumae-derived subgenome, regulates the biosynthesis of anthocyanins in developing fruit. Furthermore, independent mutations in MYB10-2 are the underlying cause of natural variation in fruit skin and flesh color in octoploid strawberry. We identified a CACTA-like transposon (FaEnSpm-2) insertion in the MYB10-2 promoter of red-fleshed accessions that was associated with enhanced expression and anthocyanin accumulation. Our findings suggest that putative cis regulatory elements provided by FaEnSpm-2 are required for high and ectopic MYB10-2 expression and induction of anthocyanin biosynthesis in fruit flesh. We developed MYB10-2 (sub-genome) specific DNA markers for marker-assisted selection that accurately predicted anthocyanin phenotypes in octoploid segregating populations.

Evolutionary history and pan-genome dynamics of strawberry ( Fragaria spp.)

“…4A), and all the MYB1s share the repressor motif "LNLDLTLS" (50), while all the MYB10s contained the promoting anthocyanin biosynthesis motif of "RPRPRTFII" (51). Previous studies have shown that fruit color mutants in strawberries were mostly associated with MYB10 (49,52,53). To reveal the cause of fruit color transition, we used the resequencing data to detect the polymorphisms of MYB10 between white and red fruited individuals for each species (Fig.…”

An LTR retrotransposon in the promoter of a PsMYB10.2 gene associated with the regulation of fruit flesh color in Japanese plum

“…The case reported in this study might be similar to that for red-skin apples, where an LTR retrotransposon in the MdMYB10 promoter was associated and functionally validated with the increased gene expression 24 . In strawberry, an LTR retrotransposon disrupting the MYB10 gene sequence was causative of the white-flesh phenotype, while in another allele a CACTA-like transposon inserted in the promoter was associated with the enhanced gene expression observed in the red fruits 14 . Outside the Rosaceae family, cases of transposons enhancing the expression of the orthologous R2R3-MYB gene have been reported in purple cauliflower, blood orange and pepper 55-57 .…”

“…Other R2R3-MYBs downregulate anthocyanin biosynthesis by diverging to other branches of the phenylpropanoid pathway or by repressing structural genes 11-13 . However, the MYB10 genes remain the main factors leading to red-to-blue fruit coloration, and DNA polymorphisms with direct impact on its expression or protein function have been identified and correlated with fruit color variation in strawberry 14 , apple 15,16 , pear 17,18 , peach 19,20 , sweet cherry 21,22 and Japanese plum 23 . Transposons have also been reported to play a role in this variability 14,24 .…”

“…However, the MYB10 genes remain the main factors leading to red-to-blue fruit coloration, and DNA polymorphisms with direct impact on its expression or protein function have been identified and correlated with fruit color variation in strawberry 14 , apple 15,16 , pear 17,18 , peach 19,20 , sweet cherry 21,22 and Japanese plum 23 . Transposons have also been reported to play a role in this variability 14,24 . Anthocyanin levels can also be modulated by ethylene production 25 and environmental factors such as light and temperature 26-28 , adding an extra layer of complexity to their regulation.…”

Integrated metabolomic and transcriptomic analysis reveals factors underlying differences in fruit quality between Fragaria nilgerrensis and Fragaria pentaphylla

“…17 Owing to the importance of bioactive compounds in the quality of strawberry fruit, increasing numbers of studies have focused on the expression of associated genes in strawberry for use in future breeding programs. 18 For example, Castillejo et al 19 found that MYB10 is the major factor that controls natural variation in the color of skin and flesh color in strawberry fruit. Similarly, Chen et al 20 found that eliminating the translational repression of FabZIPs1.1 can enhance sucrose accumulation in strawberry.…”