Plant introns differ from vertebrate and yeast introns as they are U-rich with many dicot introns containing up to 85% UA. Plant intron splicing signals (5' and 3' splice sites, branchpoint sequences and polypyrimidine tracts) are similar to those of vertebrate introns. It is expected that the UA-rich intron sequences are recognised and bound by U-rich binding proteins which aid in spliceosome assembly.

One of the key questions in plant intron splicing is which proteins recognise and interact with the UA-rich intron sequences. RNA-binding proteins with affinity for oligoU have been cloned from plants in the lab of Professor Witek Filipowicz, Basel. We are analysing the effects of over-expression of these proteins on splicing of mutants of the potato invertase mini-exon system. Further characterisation of these proteins will be carried out in collaboration with Professor Andrea Barta, University of Vienna.