CsMYB6 Mediates the Involvement of CsABCG6 in the Transport and Biosynthesis of Anthocyanins in Chaenomeles speciosa Flowers Under Drought Conditions

Chaenomeles speciosa, a plant species with high ornamental value, exhibited significant darkening of its petal coloration under drought conditions. This chromatic alteration primarily stems from anthocyanin biosynthesis and transport. Through integrated proteomic and transcriptomic analyses, we identified CsABCG6, a transporter of the ABCG subfamily, as a key regulator. The molecular docking analysis preliminarily demonstrated that CsABCG6 bound to anthocyanin monomers. Functional characterization revealed a dual role of CsABCG6 in regard to anthocyanin metabolism; it displayed anthocyanin transport activity in yeast systems, whereas transient transformation assays confirmed its capacity to enhance anthocyanin biosynthesis. Stable transformation experiments in tobacco further validated the anthocyanin-promoting function of the previously identified transcription factor CsMYB6. Yeast one-hybrid (Y1H) and dual-luciferase assays (LUC) established that CsMYB6 transcriptionally activates the CsABCG6 promoter, thus collectively defining the CsMYB6-CsABCG6 signaling module as a critical mechanism for the precise dynamic regulation of anthocyanin metabolism under drought stress.