UC San Diego

Plants face various biotic and abiotic stresses in their environment and must be able to rapidly respond to such stresses. Some of the major abiotic stresses affecting plants include drought, salinity, heavy metals, and increasing atmospheric CO2 concentrations. These stresses contribute to worldwide food shortages caused by yield penalties and loss of crop plants. The rapidly rising atmospheric CO2 concentrations, which have reached the highest level observed in human history, have already begun affecting all life on earth, including plants. Increased CO2 affects plants directly by triggering stomatal closure, and indirectly by influencing continually more extreme weather patterning. More than 80% of the worlds consumed calories are from crop plants, which are already experiencing almost 1% in yield penalties. Food insecure and developing countries have already been disproportionately affected by the decline in available food supply, which is predicted to worsen. Yield and grain filling penalties are observed due to the stress response of plants beginning with the most common and rapid response being closure of stomata. Stomata are pores present on the surface of leaves allowing for gas exchange with the surrounding environment. Stomata will close to a multitude of stimuli, but two that have been especially prevalent in the face of climate change include closure as a response to CO2, and ABA, a phytohormone produced in the presence of drought. In order to feed an ever-growing global population, mutants displaying reduced sensitivities to stresses must be identified. In an effort to identify mutant lines that may be resistant to stressors, both forward and reverse genetics screens were utilized in two different model organisms. To this end, work in new model organism Brachypodium distachyon has been done in an effort to identify novel genes involved in CO2 signaling. Brachypodium distachyon was also utilized in a reverse genetic screen to determine if the same components involved in stomatal development in Arabidopsis thaliana contributed in the same manner in grasses. Characterization of a mutant identified in a screen of ABA insensitive Arabidopsis thaliana has also been pursued and may lead to identification of important signaling components involved in drought responses. Identification of causative mutations conferring reduced sensitivity to ABA or increased CO2 concentration may be crucial in generating crop plants with lessened yield penalties in the face of the changing global climate to continue feeding the growing human population.