Species analyzed, polyadenylation [poly(A)] messenger (mRNA) identified, and poly(A) sites mapped.

aDownloaded from the NCBI Nucleotide database (http://www.ncbi.nlm.nih.gov/) with searching keywords “species name [organism] and mRNA [title]”. The downloaded sequences were mainly verified mRNA sequences, but some expressed sequence tags (ESTs) were also included if they had been submitted to GenBank under mRNA rather than ESTs. For S. bicolor, however, in order to have a sufficient number of monocot plant species analyzed, the mRNA database transcripts were supplemented with EST transcripts to ensure a large number of poly(A) sites mapped in the species. Further research is needed to test whether this supplement altered the nucleotide type frequencies of mapped poly(A) sites in S. bicolor.
bGI: NCBI sequence identification number.
cMust have met three criteria: 1) the mRNA sequence upstream of the poly(A) tail must have at least 100 bases; 2) the mRNA has a poly(A) tail at the 3′ end; and 3) the pure poly(A) tail must have at least 12 A’s.
dThe mRNA–genome mapping was set to zero tolerance for mismatches.
eNo information was available on which site is more functional than another if a unique mRNA sequence is mapped to more than one location on the genome. The species average for the number of sites per unique mRNA in the higher eukaryote group (animals and plants) was 1.36 if all the species were included, and was 1.26 when rhesus monkey and chimpanzee were excluded.