Characterization of a MYBR2R3 gene from black spruce (Picea mariana) that shares functional conservation with maize C1.

PCR amplification with degenerate primers targeted to highly conserved amino acid motifs within the MYB domain was used to demonstrate that black spruce (Picea mariana) possesses a diverse MYB gene family. Amino acid sequence comparisons revealed three broad MYB subfamilies, one of which shares extensive similarity with maize C1, a central regulator of anthocyanin biosynthesis. A cDNA clone encoding a MYBR2R3 protein from P. mariana with high levels of sequence homology to maize C1 was shown to transactivate the Bz2 promoter in combination with maize R in embryonal tissues of both black spruce and larch. Functional dependence on the maize R protein, and the presence of a conserved C-terminal GIDPxTH motif, support the conservation of MYBR2R3 function in conifers, and demonstrate that the basic components of MYBR2R3-dependent transcriptional regulation have been conserved between angiosperms and gymnosperms.