Hannah Callenius (Universität Heidelberg)
Hannah Callenius's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Universität Heidelberg in the year 2023 with the title:
Investigating the Cysteine Synthase Complex in regulating the ABA-dependent stomatal closure and the drought stress response
The master thesis showed an influence of the stability of the cysteine synthase complex during metabolic changes in cysteine metabolism during stomatal closure in Arabidopsis thaliana.
Due to the increasing extent and severity of droughts, it is very important to understand the response to drought stress in plants, which includes rapid stomatal closure to reduce water loss. Cysteine, the precursor of organic sulfur-containing molecules, can induce stomatal closure in Arabidopsis thaliana. Cysteine synthesis in three cellular compartments – the plastids, mitochondria and cytosol – requires the formation of the Cysteine Synthase Complex (CSC), a dynamically associating and dissociating protein complex of two enzymes.
This thesis focused on the role of the CSC in drought signalling and stomatal closure. Callenius analysed plants lacking the compartment-specific CSC proteins and transgenic plants with mutated CSC proteins that enhanced the stability of the protein complex. Callenius used microscopic and physiological methods to directly and indirectly determine the stomatal aperture and the accumulation of the drought hormone abscisic acid (ABA), and ultra-performance liquid chromatography (UPLC) to quantify the levels of sulfur-containing metabolites. Plants with a stabilised CSC association increased steady-state cysteine levels and induced stomatal closure, coinciding with a reduction in water loss and stomatal conductance. Using various Arabidopsis mutants, Callenius specified that this stability-induced response requires ABA and cysteine synthesis. Taken together, the results highlight a regulatory role for CSC stability during stomatal closure in response to drought signals.
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Hannah Callenius conducted this work at the Centre for Organismal Studies (COS) Heidelberg, Department Molecular Biology of Plants, in the group of Prof. Rüdiger Hell.
