AUSTRALIA—GERMANY WORKSHOP ON BIODIVERSITY

The Shine Dome, 13-17 March 2006

Activation tagging in barley and wheat
by Dr Mick Ayliffe, CSIRO Plant Industry

Activation tagging is the process of introducing a regulatory element in juxtaposition with an endogenous gene resulting in an altered transcriptional state of this gene, usually ecotopic over-expression. In some instances, over-expression generates dominant gain-of-function mutant phenotypes that provide insight into gene function. This dominant mutagenesis strategy has the potential to overcome functional gene redundancy, making it highly applicable to polyploidy species such as wheat. While this mutagenesis has been used extensively in Arabidopsis, no activation tagging systems have been successfully developed in barley and wheat. We are developing an activation tagging system in these two species using a maize Ac/Ds transposable element system. Ds elements carrying maize ubiquitin promoter sequences have been introduced into both cereal species and have been shown to transpose at frequencies sufficient for mutagenesis. Analysis of sequences flanking new insertion events in barley identifies insertion into genic and non-genic regions of the genome. Genomic integration of the activation tagging Ds element generates high levels of flanking sequence transcription. We are currently screening F2 populations of barley for morphological variants arising from either gene over-expression or insertional gene inactivation. Several potential tagged mutants have been identified.