Hanna Hõrak will defend her doctoral thesis titled „Identification of key regulators of stomatal CO2 signalling via O3-sensitivity“ on 3 May 2017 at 10:15.
Professor Hannes Kollist;
Senior Research Fellow Mikael Johan Brosché.
Jean Colcombet research scientist, Ph.D. Institute of Plant Sciences Paris-Saclay France.
Plants give us food, pharmaceuticals, clothes, paper and many other goods. Understanding how plants work is essential for breeding plants with higher yield, more useful biochemical composition or increased stress tolerance. Gas exchange with the environment determines plant growth, as CO2 uptake for photosynthesis is accompanied by water loss. CO2 enters and water vapour and oxygen leave the plant via stomata, which are pores on plant leaves formed by specialized guard cells that control the aperture of the pore. Adequate and efficient regulation of stomatal aperture in response to changing environmental conditions is essential for plants to live and thrive. Stomata close in response to darkness, elevated CO2 concentration, reduced air humidity, air pollutants such as ozone (O3), and pathogens. The plant hormone abscisic acid (ABA) is a key regulator of stomatal closure.
In this thesis, studies of the underlying causes of O3-sensitivity in several natural variants and mutants of Arabidopsis thaliana led to the identification of key components that regulate stomatal CO2 signalling. A model that describes signal transduction in guard cells in response to elevated CO2 concentration was proposed. The evolution of stomatal responsiveness to ABA and CO2 was also addressed by studying stomatal responses in ferns. Fern stomatal responses depended on species and growth conditions, indicating that large-scale analysis of stomatal behaviour of ferns with different evolutionary age and growth habitat would be necessary to better understand the evolution of stomatal responsiveness in land plants.
The results presented in this thesis bring important insight into the molecular mechanisms of plant stomatal CO2 signalling and provide useful information for further research on this topic. The obtained knowledge can be applied to develop crops with higher water use efficiency in the changing environmental conditions.