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Anthocyanin accumulation is coordinated in plants by a number of conserved transcription factors. In apple (Malus X domestica), an R2R3 MYB transcription factor has been shown to control fruit flesh and foliage anthocyanin pigmentation (MYB10) and fruit skin color (MYB1). However, the pattern of expression and allelic variation at these loci does not explain all anthocyanin-related apple phenotypes. One such example is an open-pollinated seedling of cv Sangrado that has green foliage and develops red flesh in the fruit cortex late in maturity. We used methods that combine plant breeding, molecular biology, and genomics to identify duplicated MYB transcription factors that could control this phenotype. We then demonstrated that the red-flesh cortex phenotype is associated with enhanced expression of MYB110a, a paralog of MYB10. Functional characterization of MYBllOa showed that it was able to up-regulate anthocyanin biosynthesis in tobacco (Nicotiana tabacum). The chromosomal location of MYB110a is consistent with a whole-genome duplication event that occurred during the evolution of apple within the Maloideae family. Both MYB10 and MYB110a have conserved function in some cultivars, but they differ in their expression pattern and response to fruit maturity. [ABSTRACT FROM AUTHOR]

Buds were sampled from non-flowering spurs that had developed on 1 year-old wood of four apple (Malus domestica Borkh.) cultivars during the 1998-99 growing season in order to determine the effect of cultivar on appendage formation, doming and flower morphogenesis. Cultivars differed in their pattern of appendage formation over time. The rate of appendage formation was highest in 'Fuji' and 'Pacific Rose™' and lowest in 'Braeburn' during the first 60 d after bloom (DAB). A high proportion of buds were floral in all cultivars at the end of the growing season (75-100% depending on cultivar). However, the probability of observing doming was never greater than 0.13, indicating that flower morphogenesis proceeded rapidly once buds were committed to floral development. The four cultivars each exhibited a unique pattern of floral development, as determined by fitting response probabilities to each of five ordinal stages of development with time. Doming occurred significantly earlier in 'Fuji' buds (peaking 86 DAB) than in buds of the other cultivars (peaking 104-112 DAB). Doming was initiated at the same time in buds of 'Braeburn', 'Royal Gala' and 'Pacific Rose™, but was completed earlier in 'Braeburn' than in 'Royal Gala'. The timing of floral commitment was not related either to the time of flowering, or to the time of fruit maturity of the cultivar. These observations indicate that the timing of specific events during flower morphogenesis differed between cultivars. [ABSTRACT FROM AUTHOR]