The 2012 ASHS Annual Conference

Coloration of apple fruit is attributed to accumulation of anthocyanins, a class of plant flavonoid metabolites.  Flavonoids are ubiquitous in plants, and play important roles throughout plant growth and development, and contributing to pigmentation of flowers and fruits.  MYB transcription factors (TFs) are highly abundant in plants, and play important roles in regulation of several pathways such as cellular morphogenesis, cell cycles, and secondary metabolism.  Previous efforts on characterization of structural and regulatory genes involved in fruit coloration in apple (Malus × domestica Borkh.) have elucidated roles of some genes in the anthocyanin biosynthesis pathway that contribute to  accumulation of anthocyanin in skin of apple fruit.  Moreover, three transcription factors, MdMYB10, MdMYB1, and MdMYBA have been isolated and characterized in apple, although these are likely to be allelic.  In this study, a novel apple MYB TF, designated as MdMYB3, has been isolated, characterized, and mapped to an apple linkage group. Transcripts of MdMYB3 transcript have been detected in all various tissues in apple, including leaves, flowers, and fruits.  Moreover, transcripts of this transcription factor have been compared in red- vs. yellow-colored fruit.  Functional analysis of MdMYB3 gene in tobacco (Nicotiana tabacum) revealed interesting variations in flower color pigmentation as well as other morphological characteristics.  The regulatory role of this transcription factor has been further elucidated in these studies.