Establishing gene function by mutagenesis in Arabidopsis thaliana.

The nuclear genome of Arabidopsis thaliana was sequenced to near completion a few years ago, and ahead lies the challenge of understanding its meaning and discerning its potential. How many genes are there? What are they? What do they do? Computer algorithms combined with genome array technologies have proven efficient in addressing the first two questions as shown in a recent report (Yamada et al., 2003). However, assessing the function of every gene in every cell will require years of careful analyses of the phenotypes caused by mutations in each gene. Current progress in generating large numbers of molecular markers and near-saturation insertion mutant collections has immensely facilitated functional genomics studies in Arabidopsis. In this review, we focus on how gene function can be revealed through the analysis of mutants by either forward or reverse genetics. These mutants generally fall into two distinct classes. The first class typically includes point mutations or small deletions derived from chemical or fast neutron mutagenesis whereas the second class includes insertions of transferred-DNA or transposon elements. We describe the current methods that are used to identify the gene corresponding to these mutations, which can then be used as a probe to further dissect its function.