Efficient growth and development are essential factors for plant productivity and they dependent on a number of biotic and abiotic factors. Thus, plants are susceptible to a great variety of stimuli that trigger the onset of genetically conditioned programs influencing plant development and metabolic content. Calcium has long been acknowledged as one of the most important signalling components in plants and is crucial for the activation of environmental stress responses as well as for developmental processes. Nevertheless, our overall understanding of the general principles guiding the calcium signalling cascades in regulating plant growth, development and stress response remains fragmented. It is an enigma, how a single ion, combined with a small number of calcium-sensing proteins, can integrate so many distinct environmental signals and regulate many cellular processes in a differential fashion. Understanding the role of calcium on a cellular as well as organismic level is a pre-requisite to exploit the intrinsic calcium signalling program to improve plant productivity. The ultimate goal of CROPP is to provide novel tools to improve crop productivity by manipulating calcium-regulated processes associated with stress responses, growth and development. CROPP will address the role of calcium signalling during light-dark transitions triggering developmental responses, during environmental stresses and hormone responses. To achieve these goals, the following specific objectives will be developed: (1) Determining calcium signatures in different cellular compartments during development and environmental adaptation; (2) Investigating the calcium signalosome underlying development and adaptation (e.g. changes in the phospho-proteome in different cellular compartments); (3) Elucidating the calcium-sensor interactome by employing protein micro arrays. Although most of the research proposed in CROPP will be performed with the model plant Arabidopsis, certain aspects will be tested in tomato and tobacco. Because the principles of calcium-based signalling and the involved cellular components are common to most plants, and key regulatory components are phylogenetically conserved, knowledge and results obtained by CROPP will likely contribute to future strategies for the improvement of important traits in crop plants.