Allelic Variation of <i>MYB10</i> Is the Major Force Controlling Natural Variation in Skin and Flesh Color in Strawberry ( <i>Fragaria</i> spp.) Fruit
Cristina Castillejo, Veronika Waurich, Henning Wagner, Rubén Ramos, Nicolás Oiza, Pilar Muñoz, Juan Carlos Triviño, Julie Caruana, Zhongchi Liu, Nicolás Cobo, Michael A. Hardigan, Steven J. Knapp, José G. Vallarino, Sonia Osorio, Carmen Martín‐Pizarro, David Posé, Tuomas Toivainen, Timo Hytönen, Youngjae Oh, Christopher R. Barbey, Vance M. Whitaker, Seonghee Lee, Klaus Olbricht, José F. Sánchez‐Sevilla, Iraida Amaya
Abstract
The fruits of diploid and octoploid strawberry (Fragaria spp) show substantial natural variation in color due to distinct anthocyanin accumulation and distribution patterns. Anthocyanin biosynthesis is controlled by a clade of R2R3 MYB transcription factors, among which MYB10 is the main activator in strawberry fruit. Here, we show that mutations in MYB10 cause most of the variation in anthocyanin accumulation and distribution observed in diploid woodland strawberry (F. vesca) and octoploid cultivated strawberry (F. ×ananassa). Using a mapping-by-sequencing approach, we identified a gypsy-transposon in MYB10 that truncates the protein and knocks out anthocyanin biosynthesis in a white-fruited F. vesca ecotype. Two additional loss-of-function mutations in MYB10 were identified among geographically diverse white-fruited F. vesca ecotypes. Genetic and transcriptomic analyses of octoploid Fragaria spp revealed that FaMYB10-2, one of three MYB10 homoeologs identified, regulates anthocyanin biosynthesis 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. Our findings suggest that cis-regulatory elements in FaEnSpm-2 are responsible for enhanced MYB10-2 expression and anthocyanin biosynthesis in strawberry fruit flesh.