Development of tissue-specific endophytic bacterial communities in arctic pioneer plant: Oxyria digyna

Endophytic bacteria have been the center of attention in recent years due to the potential benefits they provide to the plants that they associated with, for example, nitrogen fixation, nutrient mobilization, etc. However, the factors determining the assembly of the endophytic bacterial communities inside the plants and their functions are not yet well understood, especially about the plant microbiomes in cold climate. The goal of this study is to answer if the endophytic bacterial communities in arctic plant species; Oxyria digyna show tissue-specificity.In 2013, the micropropagated bait plants grown with minimal bacterial load were planted in the study site in Kilpisjärvi, Finland (69oN) in July 2013, then were harvested in August 2013 and in July 2014, together with wild O. digyna growing adjacent to the plots. The total endophytic bacterial communities from leaves and roots were analyzed by 16s rRNA gene-targeted PCR and next generation sequencing on ion-torrent platform. The data clearly shows that the endophytic communities from different tissues differed significantly in species richness and community diversity, as well as in the community structure. The root bacterial communities were more diverse than the leaves. The community composition from leaf and root was also significantly different from each other, and different bacterial taxa dominated the communities in different tissues. This divergence was mainly due to the differential distribution of share taxa, but we also identified 76 and 18 OTUs which were root- and leaf- specific, present only in root and leaf samples, respectively. A clear succession in endophytic root communities of micropropagated bait plants in the field was also detected, indicating the acquisition of specific community members from the rhizosphere soil. In contrast, the leaf communities of bait plants resembled closely to those of wild plants at all times which could be explained by the aerial acquisition, suggesting that leaf and root communities are partially of different origin.