Arabidopsis is a plant widely used by scientists for discovering the molecular processes underlying growth, development, environmental interactions and evolution of flowering plants. The 120 Mb genome was been completely sequenced and analysed at the end of 2000, and systematic analyses of the function of the 25,500 genes is underway. Obtaining large populations with T-DNA and transposon insertions in genes is an essential starting point for most functional genomics studies.

This project has used gene trap¹ transposon tagging to generate approximately 30,000 insertions in the Arabidopsis genome that may disrupt approximately 5,000 genes. Insertions of the transposon in intron or exon sequences in the correct orientation lead to fusions of the GUS reporter gene in frame with the disrupted gene. In many cases the resulting GUS activity can be detected by sensitive histochemical staining, revealing the tissue-specific expression of genes². The transposant population is being screened for GUS expression patterns and phenotypes in a wide variety of conditions, such as biotic and abiotic stress and during different stages of development. A database of expression patterns and phenotypes is being established to complement and extend knowledge of gene expression in Arabidopsis.

1. Sundaresan, V., Springer, P., Volpe, T., Haward, S., Jones, J., Dean, C., Ma, H., and Martienssen, R. (1995). Genes and Development 9, 1797-1810.
2. Jefferson, R. Kavanagh, A., and Bevan, M. (1987) EMBO J., 6, 3901-3907.

A consortium of 11 laboratories from 8 EU countries carries out these activities. Each consortium member generates insertion lines that are shared between all members for screening. The specific expertise of each member of the consortium is used to devise screens for gene expression and to understand gene function.

This work will significantly enhance our understanding of gene function in plants. For example, it may be possible to identify gene regulatory networks based on common expression patterns. This knowledge could be used to alter various aspects of crop performance, such as flowering time and stress resistance.

The gene trap transposon is based on a modified maize Ds transposon that contains a selectable kanamycin marker and a GUS gene with a three-frame splice acceptor. The transposon is mobilised by a T-DNA expressing Ac transposase, and transpositions to sites unlinked to the Ds launching pad are specifically selected using the iaaH counterselection marker.

Histochemical analysis of a gene trap transposant. The blue colour reveals gene expression in the base of lateral branches in the inflorescence stem, and in the developing sepals of flowers.

Participants

Belgium

Marc Zabeau, Flanders Interuniversity Institute for Biotechnology, Gent

Denmark

John Mundy, University of Copenhagen, Copenhagen

Klaus Nielsen, DFL-Trifolium, Store Heddinge

Hans Thordal-Christensen, Risoe National Laboratory, Roskilde

Germany

Gerd Jürgens, Eberhard-Karls-Universitaet Tübingen, Tübingen

Italy

Chiara Tonelli, Universita’ Degli Studi di Milano, Milano

The Netherlands

Willem Stiekema, Plant Research International, Wageningen

Spain

Javier Paz-Ares, Centro Nacional de Biotecnologia, Madrid

Switzerland

Ueli Grossniklaus; University Zurich; Zurich

United Kingdom

Denise Brown AMICA Science EEIG, Norwich,

Michael Bevan, John Innes Centre, Norwich