INTRON-MEDIATED ENHANCEMENT OF GENE-EXPRESSION IN MAIZE (ZEA-MAYS L) AND BLUEGRASS (POA-PRATENSIS L)

We report a strength comparison of a large variety of monocot and dico t intron-containing fragments inserted in the 5' untranslated leader, between the CaMV 35S promoter and the uidA gene (coding for the beta-g lucuronidase: GUS). Relative strengths of the intron-containing fragme nts were evaluated by comparing transient GUS expression after particl e bombardment in embryogenic maize and bluegrass suspension cultures. Our results confirm a dramatic dependence on the presence of an intron for chimeric gene expression in both species. On average, the maize f irst intron of ubi1 provided the highest enhancement of gene expressio n in maize and bluegrass (71- and 26-fold enhancement, respectively). Half of the introns tested affected gene expression differently in blu egrass and maize. This suggests that the intron-mediated enhancement o f gene expression generally obtained with maize may not be fully appli cable to all monocots. We also report enhancement of gene expression ( 92-fold) in a monocot species by a dicot intron (chsA intron).