Genetic modification and gas exchange analysis of stomatal conductance proteins involved in Arabidopsis thaliana and Solanum lycopersicum CO2 signaling.
- Samarasena, Shane Asanka
- Advisor(s): Schroeder, Julian I
Abstract
Due to the ongoing rise in atmospheric carbon dioxide (CO2) concentrations and other downstream effects of climate change, global crop agricultural yields are projected to be severely impacted. To combat this issue, a clear understanding of the molecular mechanisms by which plants are able to respond to increasing CO2 levels is imperative. This study serves to characterize and investigate the roles of several proteins suspected to function in CO2-induced signal transduction in Arabidopsis thaliana and Solanum lycopersicum guard cells. This research was conducted through the construction and screening of multiple mutant plant lines as well as analysis of their stomatal gas exchange responses to imposed shifts in [CO2]. Previous research has revealed the importance of the MAP kinase MPK12 in its role as an inhibitor of the Raf-like kinase HT1, a principal negative regulator of high CO2-induced stomatal closure. However, the mechanism by which this inhibitory interaction occurs is not yet confirmed. Results obtained from this study support previous findings suggesting that the phosphorylation activity of MPK12 is not required for its function in CO2 signaling through gas exchange analysis of a kinase inactive isoform. Additionally, another protein named AtMRK1 is suspected to function in guard cell CO2 signaling in tandem with two previously identified MAPKKK proteins of the same clade, named CBC1 and CBC2. Thus, a cbc1/cbc2/atmrk1 allelic triple mutant for all three genes was developed and screened for in A. thaliana to potentially observe whether AtMRK1 partially complements the activity of CBC1 and CBC2 in future analyses. Lastly, preliminary gas exchange experiments were pursued on mutant alleles of the SlROP9 protein in S. lycopersicum. The preliminary data obtained here suggest that rop9 mutants experience constitutively reduced levels of stomatal conductance with no impairment to CO2 signal transduction, and thus are likely to exhibit increased water use efficiency when compared to the wildtype allele.