Knocking It Out of the Park: Arabidopsis Mutants Don’t Display a Decrease in Fitness

Science Center, Bent Corridor

The genome sequence of the model plant Arabidopsis thaliana has been available for fifteen years, yet gene function is known for only about 10% of its 26,800 genes. At a broader level, gene function may be investigated by generating a mutant that has the gene of interest ‘knocked out’ via a tDNA insertion, so the mutant lacks the gene product. The mutant is then grown under various conditions and phenotyped for traits such as life history or morphology. As part of unPAK (Undergraduate Phenotyping of Arabidopsis Knockouts), we have been investigating the phenotypic effects of single-gene knockouts of the Columbia genotype of A. thaliana. Our set of mutants consists of 122 knockout mutant genotypes and 11 phytometers, serving as controls. These mutants have been grown twice, once with a heat stress and once under control environmental conditions. Results showed few differences in plant performance between the mutants as a group and the control phenotypes for both experimental runs. The mutant phenotypes had a wider range of variation, but were not on average, less ‘fit’ than the control phenotypes. To identify potential gene effects, we took a closer look at mutant genotypes with phenotypes that differed significantly from the control by researching previously documented information on the mutated gene using The Arabidopsis Information Resource (TAIR, www.arabidopsis.org). This allows the phenotype to be associated with a specific locus where the genes were altered, and we can see what changes when the gene is non-functioning. Issues with regulating temperature and controlling fungus growth in our experimental setup merit more trials so more can be understood about this vast genome.