INTRON CREATION AND POLYADENYLATION IN MAIZE ARE DIRECTED BY AU-RICH RNA

Intron recognition in Angiosperms is hypothesized to require AU-rich motifs within introns. In this report we examined the role of AU-rich motifs in pre-mRNA processing. AU rich segments of maize introns inserted near the single intron of the maize Bronze-9 (Bz2) gene result in alternative splicing. Other insertions of AU-rich sequence in the Bz2 cDNA resulted in de novo intron creation using splice junctions at the edges of the AU-rich region. Surprisingly, the five AU-rich inserts that we tested also caused polyadenyation, even though none had been selected 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 that in the absence of a 5' splice site, polyadenylation is the default pathway.