Red colouration in apple fruit is due to the activity of the MYB transcription factor, MdMYB10

Abstract

SummaryAnthocyanin concentration is an important determinant of the colour of many fruits. In apple (Malus · domestica), centuries of breeding have produced numerous varieties in which levels of anthocyanin pigment vary widely and change in response to environmental and developmental stimuli. The apple fruit cortex is usually colourless, although germplasm does exist where the cortex is highly pigmented due to the accumulation of either anthocyanins or carotenoids. From studies in a diverse array of plant species, it is apparent that anthocyanin biosynthesis is controlled at the level of transcription. Here we report the transcript levels of the anthocyanin biosynthetic genes in a red-fleshed apple compared with a white-fleshed cultivar. We also describe an apple MYB transcription factor, MdMYB10, that is similar in sequence to known anthocyanin regulators in other species. We further show that this transcription factor can induce anthocyanin accumulation in both heterologous and homologous systems, generating pigmented patches in transient assays in tobacco leaves and highly pigmented apple plants following stable transformation with constitutively expressed MdMYB10. Efficient induction of anthocyanin biosynthesis in transient assays by MdMYB10 was dependent on the co-expression of two distinct bHLH proteins from apple, MdbHLH3 and MdbHLH33. The strong correlation between the expression of MdMYB10 and apple anthocyanin levels during fruit development suggests that this transcription factor is responsible for controlling anthocyanin biosynthesis in apple fruit; in the red-fleshed cultivar and in the skin of other varieties, there is an induction of MdMYB10 expression concurrent with colour formation during development. Characterization of MdMYB10 has implications for the development of new varieties through classical breeding or a biotechnological approach.

Visual Tracking of Plant Virus Infection and Movement Using a Reporter MYB Transcription Factor That Activates Anthocyanin Biosynthesis

“…However, the overexpression of the MYB component is not always sufficient. Transient expression of an apple (Malus 3 domestica) MYB factor (MdMYB10) induced only a weak anthocyanin response in N. benthamiana and required the presence of a recombinant bHLH partner to fully activate the target promoters (Espley et al, 2007;Lin-Wang et al, 2010). In our case, the expression levels conferred by the different viruses or the concomitant expression of the corresponding viral RNA silencing suppressors may explain the ability of Ros1 to activate pigmentation on its own in most instances.…”

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

“…A. tumefaciens cultures harboring these plasmids were grown in liquid LuriaBertani medium at 28°C for 16 h. Bacteria were pelleted and resuspended in 10 mM MgCl 2 solution to an optical density at 600 nm of 0.7. Equal amounts of A. tumefaciens suspensions harboring each construct were infiltrated into the abaxial surface of the oldest two leaves of 4-week-old N. benthamiana plants as described by Espley et al (2007). Eight days after infiltration, photographs of infiltrated leaves were taken, and leaf samples were harvested, freeze dried, and analyzed for anthocyanins as described above.…”

MYB5 and MYB14 Play Pivotal Roles in Seed Coat Polymer Biosynthesis in Medicago truncatula

“…The MYBs specific to the anthocyanin pathway are PRO-DUCTION OF ANTHOCYANIN PIGMENTATION1 (PAP1; MYB75) in Arabidopsis and LEGUME ANTHO-CYANIN PRODUCTION1 (LAP1) in Medicago truncatula (Borevitz et al, 2000;Peel et al, 2009). Homologs of PAP1 and LAP1 have been discovered in various plant species (Espley et al, 2007;Azuma et al, 2008;Lin-Wang et al, 2010). In Arabidopsis, TT2 (AtMYB123) is the major MYB transcription factor regulating the PA biosynthesis pathway.…”