Isolation and characterization of rpoA genes encoding the rapidly evolving α subunits of plastid encoded RNA polymerases in Pelargoniums

CHED 218

Punya Navaratnarajah, navara_p@denison.edu, Sonya L. McKay, mckay@denison.edu, and Peter Kuhlman, kuhlman@denison.edu. Department of Chemistry and Biochemistry, Denison University, Granville, OH 43023
Previous studies have shown that genes encoding the plastid encoded RNA polymerases (RNAP) in plants of the genus Pelargonium are evolving at an elevated rate. RNAP is a multisubunit enzyme whose core consists of α, β, β' and β'' subunits encoded by the rpoA, rpoB, rpoC1 and rpoC2 genes, respectively. The rpoA gene, whose gene product, the α subunit, controls RNAP assembly, has the highest rate of evolution. In order to characterize rpoA genes from across the spectrum of the Pelargonium genus, we are acquiring rpoA sequences from Pelargoniums that are representative of the three main lineages in the genus. Because of the extreme rate of sequence change, PCR primers based on the sequence of known Pelargonium rpoA genes typically do not hybridize to rpoA from new species. Therefore, we are instead using primers that bind to genes known to flank rpoA in most species. The patterns and rates of evolution of the rpoA gene is explored in light of the new sequence data.