MdWRKY11 Participates in Anthocyanin Accumulation in Red-Fleshed Apples by Affecting MYB Transcription Factors and the Photoresponse Factor MdHY5

Red-fleshed apples are popular as a result of their high anthocyanin content. <i>MdMYB10</i> and its homologues are known to be important regulators of anthocyanin synthesis in apple, but the roles of other transcription factors are not well-understood. Here, we explored the role of <i>MdWRKY11</i> in regulating anthocyanin synthesis in apple flesh. Overexpression of <i>MdWRKY11</i> in apple callus could significantly promote anthocyanin accumulation, and the expression of some MYB transcription factors and structural genes increased significantly. In binding analyses, MdWRKY11 bound to W-box <i>cis</i>-elements in the promoters of <i>MdMYB10</i>, <i>MdMYB11</i>, and <i>MdUFGT</i>. However, MdWRKY11 did not interact with MdMYB10, MdbHLH3, or MdWD40 proteins, the members of the MBW complex. Sequence analyses revealed that another W-box <i>cis</i>-element was present in the promoter of <i>MdHY5</i> (encoding a photoresponse factor), and MdWRKY11 was able to bind to the promoter of <i>MdHY5</i> and promote its activity. Our findings clarify the role of <i>MdWRKY11</i> in anthocyanin synthesis in red-fleshed apple and imply that other novel genes may be involved in anthocyanin synthesis.