Intron recognition in Angiosperms is hypothesized to require AU-rich m
otifs within introns. In this report we examined the role of AU-rich m
otifs in pre-mRNA processing. AU rich segments of maize introns insert
ed near the single intron of the maize Bronze-9 (Bz2) gene result in a
lternative splicing. Other insertions of AU-rich sequence in the Bz2 c
DNA resulted in de novo intron creation using splice junctions at the
edges of the AU-rich region. Surprisingly, the five AU-rich inserts th
at we tested also caused polyadenyation, even though none had been sel
ected for that function in plants, Insertions of GC-rich sequence into
Bz2 did not cause either splicing or polyadenylation. We propose that
AU-rich moths are a general signal for RNA processing in maize and th
at in the absence of a 5' splice site, polyadenylation is the default
pathway.