Abstract: The rpoC1 gene encodes the RNA polymerase β' subunit protein, which binds to the DNA template during transcription, and the β-β' subunit complex formed with the β subunit constitutes a catalytic center for RNA synthesis. In this study, the rpoC1 gene mutations in ferns were surveyed. With Bayes factor greater than 20, HyPhy site model detected 3 positive selection sites and 541 negative selection sites; the PAML site model detected 10 positive selection sites, three of which had posterior probabilities greater than 99%. In addition, a phylogenetic tree of 64 ferns was constructed based on the maximum likelihood method. We calculated the transition rate, transversion rate, transition rate/transversion rate, synonymous substitution rate, nonsynonymous substitution rate, and synonymous substitution rate/nonsynonymous substitution rate by HyPhy to analyze the relationship between intron loss of rpoC1 gene and molecular evolution rates. The results indicate that intron loss of the rpoC1 gene might play a role in its transition rate, transversion rate and nonsynonymous substitution rate in ferns.

Key words: rpoC1, intron, positive selection site, selection pressure