Characterising developmental mutations in Arabidopsis thaliana

Downs J and Jones B

The University of Sydney.

Arabidopsis thaliana is a small, flowering eudicot. This unassuming plant is ideal for genetic research due its small genome and relatively rapid life cycle. These traits make A. thaliana one of the most well-studied plants and yet there is still much that can be gleaned from this plant in terms of understanding general plant function. Reproduction is one of the most important parts of plant life. Understanding how plant reproduction works on a molecular genetic scale can potentially lead to improved crop yields. In this study, two separate mutations were studied in T-DNA insertional mutants. The mutations are associated with fertilisation and embryogenesis, respectively. The mutations and their phenotypes are being characterised to improve the understanding of plant reproductive processes. Embryo termination occurs in 25% of seeds in plants hemizygous for the embryogenesis mutation. The seeds can be distinguished early in development as they appear white, as opposed to the other (75%) green seeds in the siliques. The embryogenesis mutation appears to be monogenic, recessive and homozygous lethal. Embryos within the white seeds are halted at early stages of development and bear aberrant cell division. This causal mutation is being located by whole-genome re-sequencing using an Illumina platform. The second reproductive mutation in this study, the fertilisation mutation was first observed in an arf1 homozygous arf2 heterozygous mutant line. In this line, progeny from self-crossing had a non-Mendelian ratio of genotypes. Novel techniques and confocal microscopy are currently in development to observe the movement of fluorescently labelled pollen tubes within the styles of the flowers. This will help to determine if the phenotype is due to pollen growth, parental influence or aberrant embryogenesis creating the biases in the genotypes. Ultimately, characterising these mutations will help improve knowledge of plant reproductive biology.