The directed control of protein activity plays a crucial role in the regulation of growth and development of multicellular organisms. Different post-translational control mechanisms are known to influence the activity of proteins. Here, I am proposing a novel way to control the activity of proteins that function as multimeric complexes. MicroProteins, are small single-domain protein species that can influence target proteins by sequestering them into non-productive protein complexes. I have developed the concept of microProtein function and subsequently started to identify novel microProtein regulators in the model plant Arabidopsis. The aim of this proposal is to use the microProtein concept and build synthetic microProtein modules in economical import crop plants. By combining synthetic biology approaches with modern plant breeding, we intent to re-wire plant development and alter the flowering behaviour of rice. In addition, we will use a combination of artificial microProteins and microProtein-resistant transcription factors to modify the inclination angle of leaves in rice and the bioenergy model species Brachypodium distachion. Modification of the leaf angle will allow us to grow crops at higher densities, thus having the potential to increase both biomass and seed production per acreage. Finally, we aim to identify novel, evolutionary conserved microProtein-modules and unravel the mechanism of microProtein function, to study their role in plant development and adaptation.