Fig. 1.

Duplications of Pol V subunits are coincident with the emergence of the grass family Poaceae. The evolutionary relationships of NRPE1 (A) and NRPD/E2 (B) within the monocot lineage demonstrate that monocots outside of the Poaceae family have a single gene copy (blue box), while most members of Poaceae have paralogous genes (green and yellow boxes). Phylogenetic trees were inferred by maximum likelihood analysis of mRNA sequence in the catalytic domain (regions B to H). Bootstrap support values <100 are shown and red stars mark the inferred duplications. Thick branches indicate positive selection (P < 0.05). Full species names and gene accession numbers are listed in supplementary table 1, Supplementary Material online. (C) RT-PCR demonstrates that all Oryza sativa paralogs are expressed.