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Open Access Highly Accessed Research article

An apple MYB transcription factor, MdMYB3, is involved in regulation of anthocyanin biosynthesis and flower development

Sornkanok Vimolmangkang12, Yuepeng Han3, Guochao Wei3 and Schuyler S Korban14*

Author Affiliations

1 Department of Natural Resources and Environmental Sciences, University of Illinois, 1201 W. Gregory, Urbana, IL 61801, USA

2 Department of Pharmacognosy, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330, Thailand

3 Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Moshan, Wuhan 430074, P. R C

4 Department of Biology, University of Massachusetts, Boston, Boston, MA 02125, USA

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BMC Plant Biology 2013, 13:176  doi:10.1186/1471-2229-13-176

Published: 7 November 2013

Abstract

Background

Red coloration of fruit is an important trait in apple, and it is mainly attributed to the accumulation of anthocyanins, a class of plant flavonoid metabolites. Anthocyanin biosynthesis is genetically determined by structural and regulatory genes. Plant tissue pigmentation patterns are mainly controlled by expression profiles of regulatory genes. Among these regulatory genes are MYB transcription factors (TFs), wherein the class of two-repeats (R2R3) is deemed the largest, and these are associated with the anthocyanin biosynthesis pathway. Although three MdMYB genes, almost identical in nucleotide sequences, have been identified in apple, it is likely that there are other R2R3 MYB TFs that are present in the apple genome that are also involved in the regulation of coloration of red color pigmentation of the skin of apple fruits.

Results

In this study, a novel R2R3 MYB gene has been isolated and characterized in apple. This MYB gene is closely related to the Arabidopsis thaliana AtMYB3, and has been designated as MdMYB3. This TF belongs to the subgroup 4 R2R3 family of plant MYB transcription factors. This apple MdMYB3 gene is mapped onto linkage group 15 of the integrated apple genetic map. Transcripts of MdMYB3 are detected in all analyzed tissues including leaves, flowers, and fruits. However, transcripts of MdMYB3 are higher in excocarp of red-skinned apple cultivars than that in yellowish-green skinned apple cultivars. When this gene is ectopically expressed in Nicotiana tabacum cv. Petite Havana SR1, flowers of transgenic tobacco lines carrying MdMYB3 have exhibited increased pigmentation and accumulate higher levels of anthocyanins and flavonols than wild-type flowers. Overexpression of MdMYB3 has resulted in transcriptional activation of several flavonoid pathway genes, including CHS, CHI, UFGT, and FLS. Moreover, peduncles of flowers and styles of pistils of transgenic plants overexpressing MdMYB3 are longer than those of wild-type plants, thus suggesting that this TF is involved in regulation of flower development.

Conclusions

This study has identified a novel MYB transcription factor in the apple genome. This TF, designated as MdMYB3, is involved in transcriptional activation of several flavonoid pathway genes. Moreover, this TF not only regulates the accumulation of anthocyanin in the skin of apple fruits, but it is also involved in the regulation of flower development, particularly that of pistil development.

Keywords:
Anthocyanin; Apple; MYB transcription factors; Malus × domestica; Flavonoids; Reproductive tissues