Bacterial seed endophyte community of annual plants modulated by plant photosynthetic pathways

Climate change is predicted to have adverse impacts on terrestrial ecosystems and uncertainties exist on how these systems will respond. Terrestrial plant ecosystems can be divided by how they fix atmospheric carbon- C3, C4 and CAM photosynthesis pathways. However, as for now, no clear answers could be given regarding the future global repartition of the C3, C4 and CAM plants. As seeds are the reproductive and dispersal unit of the plants and endophytes play a central role in their preservation; here it is suggested that a better knowledge regarding the seeds endophytic community is needed when studying the future repartition of C3, C4 and CAM plant seeds. Bacterial endophyte communities inhabiting seeds belonging to C3, C4 and CAM annual plants were analysed by culture-dependent methods and 16S rRNA gene sequencing. Results indicated there were differences in the relative abundance of bacterial phyla within and across all photosynthetic pathways. Indicating some level of niche partitioning, and each of the three photosynthetic pathways could be characterized by a specific endophytic composition of Firmicutes, corresponding to the adaptation capacity of each group. We successfully identified resistant species of endophytes in the Firmicutes phylum of C4 and CAM plant seeds. Those bacteria are known for being involved in thermal regulation and plant protection through enzymes and antibiotic synthesis and match the strong adaptation capacity of C4 and CAM plants. Overall, this study suggests that there is a plant-mediated selection of the seed microbiome and these symbionts could potentially confer additional benefits to the seed.