The genomic architecture of competitive response of Arabidopsis thaliana is highly flexible between monospecific and plurispecific neighborhoods.

Although plants simultaneously interact with multiple neighboring species throughout their life cycle, there is still very limited information about the genetics of the competitive response in the context of plurispecific interactions. Using a local mapping population of Arabidopsis thaliana, we set up a Genome Wide Association study to estimate the extent of genetic variation of the competitive response in presence of 12 plant species assemblages, and to compare the genetic architecture of the competitive response between monospecific and plurispecific neighborhoods. Based on four phenotypic traits, we detected strong crossing reaction norms not only among the three monospecific neighborhoods, but also among the different plant assemblages. Accordingly, the genetic architecture of the competitive response was highly dependent on the identity and the relative abundance of the neighboring species. In addition, enriched biological processes underlying the competitive response largely differ between monospecific and plurispecific neighborhoods. In particular, receptor-like kinases and transporters were significantly enriched in plurispecific neighborhoods. Our results suggest that plants can integrate and respond to different species assemblages depending on the identity and number of each neighboring species, through a large range of genes associated mainly with perception and signaling processes leading to developmental and stress responses.