XVI International Botanical Congess

Splicing and splice site selection are one level at which gene expression is regulated. Exon bridging interactions have only recently been described in plant splicing. In vertebrates a minimum exon size of 50 nt is needed for interactions between factors at the adjacent splice sites across the exon. With mini-exons (<50 nt) exon bridging interactions are impeded and intron splicing enhancers are required. One of the smallest exons discovered in plants to date is a 9 nt mini-exon found within invertase genes. A putative branchpoint and U-rich sequence in the upstream intron are required for mini-exon inclusion. These may function via exon bridging interactions between factors at these elements and the 5' splice site of the downstream intron to allow splicing of the mini-exon.