Pirko Jalakas: Unravelling signalling pathways contributing to stomatal conductance and responsiveness
Plants, the primary producers on Earth, use energy from sunlight to convert carbon dioxide (CO2) and water from the soil to produce organic compounds and oxygen, both of which are needed by humans and other heterotrophic organisms. In the epidermis of the aerial parts of plants are stomata, microscopic pores surrounded by a pair of guard cells that control gas exchange between the leaf and the atmosphere, i.e., the uptake of CO2 for photosynthesis and the loss of water via transpiration. Guard cells integrate internal and various environmental signals such as light, CO2, temperature and humidity to regulate the opening and closing of stomatal pores. These stomatal movements are accomplished by changes in guard cell turgor, which are driven by the uptake or release of osmotically active ions. In future climate change scenarios, atmospheric CO2 concentrations and temperature will continue to rise, whereas precipitation will decrease in some areas and increase in others. These phenomena affect the frequency and severity of drought periods and flooding, which in turn will influence agriculture by reducing crop yields, thereby affecting food availability. It is important for plants to respond and adapt to these changing conditions. Accurate control of stomatal aperture influences biomass production and plant water management. Therefore, one important focus of plant breeding is to develop more water use efficient plants with reduced transpiration and stomatal conductance. On the other hand, low stomatal conductance is associated with reduced photosynthesis and could limit growth. Therefore, it is reasonable to assume that there exists a threshold value below which the further reduction in stomatal conductance results in a negative effect on yield. Furthermore, reduced transpiration results in reduced leaf cooling, which is important under warm temperatures. Thus, understanding the mechanism behind stomatal regulation gives valuable information for breeding crop plants for different climatic conditions.
The scientific work of Pirko Jalakas focused on stomatal regulation on different timescales: regulation of stomatal movements in response to the plant hormone abscisic acid (ABA) and environmental factors, which can take place within minutes to hours and regulation of stomatal conductance via stomatal density, which takes place over a longer timescale.
Protein kinase OST1 has an important role, a positive regulator in ABA signalling pathway, in stomatal responsiveness to environmental factors. Furthermore, the role of protein farnesylation, a post-translational modification of proteins, in regulating stomatal movements was studied, as well as the phenotypes of different proposed ABA transporters. Stomatal regulation is important for plant productivity and stress tolerance, even more so under climate change conditions. This is why understanding the fundamental principles of stomatal development, opening and closure is important: it serves to modify the water economy of model plants and crops according to the prevailing conditions in their geographical area.
More information: http://dspace.ut.ee/handle/10062/64780