EXO70 exocyst subunits in morphogenesis and adaptation

Land plants have colonized almost all surfaces of our planet. A key to their success was the evolution of morphological, physiological and regulatory features that allowed these sessile organisms to establish themselves and to function efficiently in adverse and ever changing environments. This is reflected in an unmatched developmental plasticity of plants by which growth can be adjusted to environmental conditions. Growth is tightly linked to the secretory pathway, which is not only essential to deliver building materials for membranes and cells walls during cell expansion, but also for many signalling pathways that regulate growth and development. An important cellular module regulating the targeting of secretory vesicles to specific parts of membranes is the exocyst complex. We propose to dissect the functional role of specific subunits of the exocyst complex and their alleles for growth and developmental processes and stress responses. This will have strong implications for our understanding of land plant evolution, adaptation and function, as well as for the molecular function of the exocyst complex.

Land plants have colonized almost all surfaces of our planet. A key to their success was the evolution of morphological, physiological and regulatory features that allowed these sessile organisms to establish themselves and to function efficiently in adverse and ever changing environments. This is reflected in an unmatched developmental plasticity of plants by which growth can be adjusted to environmental conditions. Growth is tightly linked to the secretory pathway, which is not only essential to deliver building materials for membranes and cell walls during cell expansion, but also for many signalling pathways that regulate growth and development. An important cellular module regulating the targeting of secretory vesicles to specific parts of membranes is the exocyst complex. In this project, we aimed to dissect the functional role of specific subunits of the exocyst complex and their alleles for growth and developmental processes and stress responses. For this, we established methods and technologies that allowed us to conducted association genetic studies to identify the roles of specific exocyst family members in particular stress responses, as well as in trichome development and function. We could identify multiple specific exocyst genes that are excellent candidates for being subfunctionalized paralogues of the exocyst family. We furthermore, dissected the role of one particular EXOCYST gene (EXO70A3) that has a role in determining root growth direction and could show that its gene dose is crucial for its molecular function. Overall, our results give further support to a model in which exocyst paralogs have subfunctionalized in land plants, a model which has strong implications for our understanding of land plant evolution, adaptation and function, as well as for the molecular function of the exocyst complex.