This issue of Functional Plant Biology is dedicated to actinorhizal plant research, covering part of the work presented at the 16th International Meeting on Frankia and Actinorhizal Plants, held in Oporto, Portugal, 5-8 September 2010. The meeting focused on several aspects of actinorhizal plants, Frankia and their association, ranging from the molecule to the ecosystem level. A similar issue dedicated to Frankia research is being published in Archives of Microbiology.