Identifying Genes Regulating Stomatal Density in Different Carbon Dioxide Levels in Arabidopsis thaliana

Anthropogenic impacts on atmospheric CO2 concentration ([CO2]) are expected to cause changes to plant morphology. Specifically, alterations are anticipated in the stomatal density (SD) of Arabidopsis thaliana. Previous studies have suggested that in elevated [CO2], SD decreases as the plant acquires the same amount of [CO2] through fewer stomata, leading to reduced water loss and improved water use efficiency. Whilst some genes involved in the SD response to fluctuations in [CO2] have previously been identified, this thesis aimed to discover further genes within this pathway. Additionally, an aim was set to examine which genes had the largest control of variance in a population of recombinant inbred lines (RILs), derived from 19 parental ecotypes. This set of RILs, known as the Multi-Parent Advanced Generation Inter-Cross (MAGIC) lines, were produced for such experiments. Once sufficient diversity in SD and SD response to changes to [CO2] had been established in the 19 parental ecotypes, a Quantitative Trait Loci (QTL) analysis was carried out to identify regions of the genome associated with control of SD and SD response to [CO2]. This analysis identified 3 QTLs which controlled SD, located on chromosomes 1, 2 and 5. There were 3 QTLs present in ambient [CO2] and 1 of these QTLs was also observed in elevated [CO2]. No QTLs identified regarding the difference in SD between [CO2] treatments were found. The QTLs on chromosomes 2 (QTL2) and 5 (QTL5) had likely genes identified Further analysis of both QTL2 and QTL5 were carried out to study their role in controlling SD in the MAGIC parental lines. Genomic data and expression data were analysed to try and identify the mechanism by which QTL2 and QTL5 affected SD.