FtMYB16 interacts with Ftimportin-α1 to regulate rutin biosynthesis in tartary buckwheat.

Fagopyrum tataricum is an ancient dicotyledonous crop and is well known to enrich in flavonoids, such as rutin. The Subgroup 4 of R2R3-MYB transcription factors, FtMYB11, FtMYB13, FtMYB14, FtMYB15 and FtMYB16 are key repressors of rutin biosynthesis in buckwheat. However, the regulatory mechanism of FtMYB16 on rutin biosynthesis is still unclear. Transcriptomics analysis showed that FtMYB16 is highly expressed in root and tightly co-expressed with the multidrug and toxic compound extrusion (MATE) transporter gene FtMATE1, which could transport isoquercitrin and promote rutin accumulation. Electrophoretic mobility shift assay (MESA), chromatin immunoprecipitation (ChIP) assay, transient activation assay and transgenic hairy roots showed that FtMYB16 directly repressed the FtMATE1 gene expression and rutin biosynthesis pathway. Yeast two hybrid screening and bimolecular fluorescence complementation assay showed that the FtMYB16 repressor interacted with an importin-α protein Ftimportin-α1 in the nucleus and cytoplasm, depending on the nuclear localization signal (NLS) of FtMYB16. Translocation assay and transient activation assay demonstrated that Ftimportin-α1 directly mediated the nuclear localization of FtMYB16 to execute the repression activity. Our findings figure out the role of MATE transporter in rutin metabolism and establish a model of MYB TFs/importin-α complex in the nucleo-cytoplasmic trafficking pathway in plants, which may be useful for the design of artificially modified metabolic pathway. Keywords: Importin, MATE transporter, MYB transcription factor, Nucleo-cytoplasmic trafficking, Rutin, Buckwheat. This article is protected by copyright. All rights reserved.