Bacterial and Fungal endophytes in Acer campestre and Acer platanoides

Despite the increasing interest on foliar endophytic microorganisms, there is only a limited number of studies investigating these microorganisms in plant pathogen infected leaves as compared to apparently healthy ones. Hence, we analyzed bacterial and fungal endophyte communities in leaves with and without green islands, as induced by endophytic fungal species, in the tree species of Acer campestre L. and A. platanoides L. using large-scale metabarcoding. The abundances of the predominant fungal and bacterial communities differed between the two Acer species, resulting in Acer species-specific responses of these communities towards infection. Endophyte diversity and community composition in leaves of A. campestre were significantly affected by site and infection and/or leaf typestatus, while endophyte diversity and bacterial community composition in A. platanoides were only affected by site. However, leaf type status significantly altered fungal community composition in A. platanoides. These findings suggest that bacterial and fungal communities responded in different ways to fungal infections. We further recorded Acer-species specific differences in microbial interactions. The abundances of positive intra-domain interactions within bacterial communities of A. campestre strongly increased in green island tissues compared to control leaves, while the opposite was observed for A. platanoides. The current study provides first insights into the complex interaction between fungal and bacterial endophytes in infected leaves of A. campestre and A. platanoides.