Gleaning Euglenozoa-specific DNA polymerases in public single-cell transcriptome data

Multiple genes encoding family A DNA polymerases (famA DNAPs), which are
evolutionary relatives of DNA polymerase I (PolI) in bacteria and phages,
have been found in eukaryotic genomes, and many of these proteins are used
mainly in organelles. Among members of the phylum Euglenozoa, distinct
types of famA DNAP, PolIA, PolIBCD+, POP, and eugPolA, have been found. It
is intriguing how the suite of famA DNAPs had been established during the
evolution of Euglenozoa, but the DNAP data have not been sampled from the
taxa that sufficiently represent the diversity of this phylum. In
particular, little sequence data were available for basal branching
species in Euglenozoa until recently. Thanks to the single-cell
transcriptome data from symbiontids and phagotrophic euglenids, we have an
opportunity to cover the “hole” in the repertory of famA DNAPs in the deep
branches in Euglenozoa. The current study identified 16 new famA DNAP
sequences in the transcriptome data from 33 phagotrophic euglenids and two
symbiontids, respectively. Based on the new famA DNAP sequences, the
updated diversity and evolution of famA DNAPs in Euglenozoa are discussed.