Calcium Regulation of Chloroplast Development & Function

Chloroplasts are the place of photosynthesis in plants. Here CO2 from the atmosphere is converted into organic matter and also all oxygen we breathe results from photosynthesis where water is split into oxygen and hydrogen. The complex performing this essential reaction for all life on earth is called photosystem II (PSII) and is stabilized by calcium ions (Ca2+). Therefore, chloroplasts contain significant amounts of calcium. However, that is obviously not the only role of calcium in chloroplasts because the total and free concentration of calcium ions can vary considerably, thus calling for an involvement of Ca2+-binding proteins in the regulation of such dynamics. Ca2+ is a well-known signalling molecule, also referred to as secondary messenger. Ca2+ ions are involved in many biological processes such as contraction of muscles or generation of signals in the nervous system in animals. Similarly, also plants employ Ca2+ ions for a diverse set of functions for regulating their physiological acclimation to changing environmental conditions. Recent research of our group uncovered two chloroplast proteins - LENA and LENB which could be involved in binding of Ca2+ ions. Plants lacking these proteins, exhibited a strong delay in chloroplast development and where chlorotic, thus indicating that they are involved in chloroplast development. These proteins are quite small in size and they are evolutionarily conserved in all higher plants and eukaryotic algae but their biological function is still enigmatic. To unravel the functional role of LENA and LENB proteins in chloroplast development, this project does address three key questions: Their impact on Ca2+ homeostasis in chloroplasts, their regulation of chloroplast development and their influence on chloroplast function, especially photosynthesis. Anticipated outcomes include the identification of LENA/B`s interaction partners, shedding light on their molecular functions. This research will make important contributions to the understanding of chloroplast development and regulation and provide novel insights with broad implications for plant physiology and potentially also agriculture.