On 27 June at 10:15 Kadri Tõldsepp will defend her doctoral thesis „The Role of Mitogen-Activated Protein Kinases MPK4 and MPK12 in CO2-induced Stomatal Movements“.
Senior Research Fellow, PhD Yuh-Shuh Wang
Professor, PhD Hannes Kollist
Senior Research Fellow, PhD Mikael Johan Brosché
Professor, PhD Toshinori Kinoshita, Nagoya University, Japan
Plants are essential to life on Earth – in the process of photosynthesis, they convert carbon dioxide (CO2) and water into organic compounds, and oxygen is released as a by-product. Stomatal pores, that are on the surfaces of the majority of the aerial parts of plants, facilitate gas exchange between plants and the external atmosphere. Each stomatal pore is surrounded by two highly specialized guard cells which sense various endogenous and environmental stimuli, such as CO2, light, temperature, hormones and pathogens and adjust the stomatal pore size to balance CO2 uptake for photosynthesis and loss of water vapour through transpiration. Since water availability is a major constraint of crop yield and is the single most important factor limiting food production, appropriate control of stomatal pore size is essential for the optimization of plant growth. Continuing rise in atmospheric [CO2] increases [CO2] inside the leaves and causes a reduction in stomatal apertures. This, in turn, reduces water loss from plants. Thus, CO2-induced stomatal closure may improve plant water use efficiency and optimization of CO2-controlled stomatal movements may enable breeding of crops that conserve water while maximizing photosynthesis. Presently, the molecular mechanisms by which plants sense CO2 concentration and transduce the CO2 signal to regulate water loss, are not fully understood. This thesis contributes to the understanding of the mechanism how the CO2 signal is transduced in the guard cells and proposes a new model for stomatal CO2-signalling. This study revealed that mitogen-activated protein kinases (MPKs) MPK4 and MPK12 are among the earliest CO2 signalling components presently known in guard cells and that CO2-signal is transmitted through MPK4 and MPK12 leading to activation of guard cell anion channels and closing of stomata. With the continuous increase in atmospheric CO2 levels and the need for breeding crops that would display optimal water use efficiencies, these findings are important for developing strategies for breeding crops suitable for future climates by specific modulation of CO2-dependent stomatal movements.