Development of an Activation Tagging System to Identify Traits in Maize

Activation Tagging, using transcriptional enhancers distributed throughout the genome to increase transcription of nearby genes, is a powerful tool for discovering gene function.  We have developed a transposable element system to distribute a novel activation tagging element throughout the genome in maize.  The transposon system is built from the En/Spm transposon system and uses an engineered seed color marker to observe excision of the transposon.  Both somatic and germinal excision events can be easily detected by evaluating kernel color.  The activation tagging element is in an En-derived non-autonomous transposon and contains 4 copies of the sugarcane bacilliform virus (SCBV) enhancer and a selectable marker.  We have demonstrated that the transposon can give rise to germinal excision events and that it can re-integrate into the genome at locations un-linked to the original integration site.  The transposon has remained active for 3 generations and events displaying high rates of germinal excision in the T2 generation have been identified.  This system is capable of generating large numbers of activation tagged maize lines that can be screened for agriculturally-relevant phenotypes.