UnPAK-ing Gene Function: Using Knockout Mutants to Identify Genes that Alter Life HistoryTraits in Arabidopsis under Heat Stress

Science Center, Bent Corridor

Despite having full genome sequences for many species, the functions of most genes in those genomes remain unknown. 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. Gene function is often investigated by generating a mutant that has the gene of interest ‘knocked out’, 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. In some cases, gene function remains unclear because the effects of the knockout mutation are phenotypically visible only under stressful conditions. As part of unPAK (Undergraduates Phenotyping Arabidopsis Knockouts), a collaborative project involving 11 institutions, we are investigating the phenotypic effects of 204 different knockouts in the Columbia genotype of A. thaliana. We are comparing the phenotypes of mutants to the unaltered genotype and 10 other A. thaliana genotypes representing natural populations. We exposed our plants to short-term extreme heat stress just before the plants transitioned from vegetative to reproductive growth then phenotyped plants from the germination stage through senescence. We have completed growth of the heat stress plants and are now repeating the experimental setup under nonstressful conditions for comparison, to identify genes whose role (absence) is revealed under heat stress. Our results advance the understanding of gene function and interesting mutant phenotypes in the research of plant functional genomics.