Fruit skin color and the role of anthocyanin

Fruit skin coloration is a unique phase in the life cycle of fruiting plants and is mainly attributed to anthocyanin pigments. Anthocyanins are the largest and most diverse group of plant pigments derived from the phenyl propanoid pathway. They are water-soluble phenolic compounds that form part of a large and common group of plant flavonoids. Coloration encompasses several physiological and biochemical changes that happen through differential expression of various developmentally regulated genes. Due to research importance and economic value, Arabidopsis thaliana (chromosome no. = 5) and Vitis vinifera (chromosome no. = 19) have been used for investigations of the structural genes involved in anthocyanin biosynthesis. Thus for this review, V. vinifera is used as a model crop. In anthocyanin biosynthesis, a wide range of constructive genes including phenylalanine ammonia lyase, chalcone synthase and anthocyanidin synthase that are regulated by MYB transcription factors are involved. These genes are coordinately expressed and their levels of expression are positively related to the anthocyanin concentrations. Expression or suppression of the constructive genes contributes to a variety of changes that make fruits visually attractive and edible. Transgenic approaches also have discovered a strong relationship between phenyl propanoid/flavonoid gene expressions for fruit skin coloration. In this study, various developments that have taken place in the last decade with respect to identifying and altering the function of color-related genes are described.