Abiotic environmental stresses such as extreme temperatures represent serious threats to plants and are a main reason for significant agricultural crop losses every year. Hence, an understanding of the molecular consequences of stress exposure and the underlying principles of plant stress responses are fundamental questions in biology and provide the basis for the genetic engineering of stress resistant crop plants. In particular, high temperature stress leads to an increase in protein unfolding, misfolding, and aggregation and thus challenges proteome homeostasis (proteostasis). As a response, cells increase the expression of molecular chaperones to maintain proteostasis by counteracting protein misfolding and aggregation.The overall goal of this study is to globally identify properties of fragile proteins in plant proteomes challenged by heat-shock exposure. We will use the unicellular green algae Chlamydomonas reinhardtii and Nannochloropsis sp. as model organisms to monitor protein misfolding and aggregation under physiological conditions, mild stress and severe temperature stress. We will apply quantitative proteomics and bioinformatics to reveal physicochemical properties characteristic for proteins prone to misfolding and aggregation. By this, we will further identify proteins that have a high dependence on protection by molecular chaperones. Based on this system-wide analysis individual proteins will be engineered with the goal to optimize their conformational stability for improved stress tolerance.