Recently Duplicated Maize R2R3 Myb Genes Provide Evidence for Distinct Mechanisms of Evolutionary Divergence after Duplication

Plant Physiology, Vol. 131, pp. 610-620

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Recently Duplicated Maize R2R3 Myb Genes Provide Evidence for Distinct Mechanisms of Evolutionary Divergence after Duplication

Anusha P. Dias,1 Edward L. Braun,1 Michael D. McMullen, and Erich Grotewold*

Department of Plant Biology and Plant Biotechnology Center, Ohio State University, Columbus, Ohio 43210 (A.P.D., E.G.); Department of Zoology, University of Florida, Gainesville, Florida 32611 (E.L.B.); and Plant Genetics Research and Plant Science Units, United States Department of Agriculture-Agricultural Research Service, University of Missouri, Columbia, Missouri 65211 (M.D.M.)

R2R3 Myb genes are widely distributed in the higher plants and comprise one of the largest known families of regulatory proteins.Here, we provide an evolutionary framework that helps explainthe origin of the plant-specific R2R3 Myb genes from widely distributed R1R2R3 Mybgenes, through a series of well-established steps. To understand the routes of sequence divergence that followed Myb gene duplication, we supplemented the information available on recently duplicated maize (Zea maysR2R3 Myb genes (C1/Pl1and P1/P2) by cloning and characterizing ZmMyb-IF35 and ZmMyb-IF25.These two genes correspond to the recently expanded P-to-A groupof maize R2R3 Myb genes. Although the origins of C1/Pl1 and ZmMyb-IF35/ZmMyb-IF25are associated with the segmental allotetraploid origin of themaize genome, other gene duplication events also shaped the P-to-Aclade. Our analyses indicate that some recently duplicated Mybgene pairs display substantial differences in the numbers of synonymoussubstitutions that have accumulated in the conserved MYB domainand the divergent C-terminal regions. Thus, differences in theaccumulation of substitutions during evolution can explain inpart the rapid divergence of C-terminal regions for these proteinsin some cases. Contrary to previous studies, we show that thedivergent C termini of these R2R3 MYB proteins are subject topurifying selection. Our results provide an in-depth analysisof the sequence divergence for some recently duplicated R2R3 Mybgenes, yielding important information on general patterns of evolutionfor this large family of plant regulatory genes.


This work was supported in part by the National Science Foundation (grant nos. MCB-9974474 and MCB-9896111 to E.G.), by the U.S. Department of Agriculture (fellowship no. USDA 1999-01582 to E.L.B.), and by the U.S. Department of Agriculture-Agricultural Research Service (research funds to M.D.M.).

1 These authors contributed equally to this paper.

* Corresponding author