Among the conserved proteins of the polyadenylation complex, seen in all eukaryotes (including the highly-reduced polyadenylation complex in Giardia) is the enzyme that adds the poly(A) tail – polynucleotide adenylyltransferase or, more colloquially, poly(A) polymerase. One would think that the evolutionary history of such a core component of the gene expression machinery would be rather unremarkable – it should be present at the outset and pretty much conserved throughout evolutionary history.
Of course, reality is much more interesting. A former student of mine did her thesis on Arabidopsis poly(A) polymerases, characterizing the four (4!) genes and the protein isoforms. A former postdoc in the lab had done some work in rice poly(A) polymerase genes, and found an equally interesting multiplicity of genes as well as some fascinating expression characteristics. This work has been recently published in PLoS ONE; as is my custom, this post is intended to point out the paper and invite (here or at the journal’s site for the paper) comment, discussion, and criticism.
A brief recap and one or two of the more provocative findings: