Identification of a conserved cassette exon event associated with the TFIIIA gene in Arabidopsis and rice. (A) Exon-inclusion (EI) and exon-skipping (ES) isoforms of TFIIIA transcripts in Arabidopsis and rice (red boxes represent cDNA/EST alignments indicating exon locations; green boxes represent predicted gene models; orange boxes represent predicted coding regions). (B) A conserved ES event associated with AtTFIIIA (At1G72050) and OsTFIIIA (Os05G03020) and the sequence alignment (BLAST parameters: −W 7 –F F) between orthologous exon skipped/included (gray box) and the flanking constitute orthologous exons (green box, the second and third C2H2 zinc finger). The inclusion of the skipped/included exon introduces an in-frame stop codon (red triangle in the top panel and red text in the alignments of the bottom panel). OsTFIIIA Exon5 has higher similarity to AtTFIIIA cassette exon (Exon3) than OsTFIIIA Exon4 (81% vs. 74%).
