Poster: Evolution of developmental & physiological mechanisms

Abs # 819: Functional Characterization of Evolutionary Conserved MYB Domain Residues Using P1 as a Model

Presenter:	Heine, George F., Heine.22@osu.edu
Authors	Heine, George F. (A)   Grotewold, Erich  (A)
Affiliations:	(A): Plant Cellular and Molecular Biology, The Ohio State University

MYB domain proteins are conserved transcriptional regulators that are found in all eukaryotes. These transcriptional regulators include the widely distributed R1R2R3 MYB proteins represented in animals by the c-MYB proto-oncogene and in plants by both the pc-MYB and the R2R3 MYB gene families, the latter of which has expanded dramatically in higher plants. Some residues within the MYB domain have remained absolutely conserved in all eukaryotes while others are conserved only in the higher plants R2R3 MYB proteins. We have utilized the Zea mays P1 protein, which belongs to the recently expanded P-to-A clade, to investigate the functional and structural roles of several residues found within the MYB domain. These residues are either highly conserved among all MYB domains or uniquely present among some MYB sub-families. Our studies focused on the Cys53, which is absolutely conserved in all MYB domains, and Cys49, which is present in just the typical R2R3 MYB domains, respectively. In addition, we also investigated the significance of the Pro63 change to Ala, a landmark of the P-to-A group of R2R3 MYB proteins in the grasses. Other residues characteristic to all plant R2R3 MYB proteins include the replacement of the first Trp of the R3 MYB repeat by a hydrophobic amino acid and the insertion of a Leu residue in the R2 MYB repeat. The significance of these two residues was also investigated. Our studies provide surprising insights on how function has been influenced by the single amino acid changes that shaped the evolution of the MYB gene family.