Plant microbiomes and biotic stress

Changes in biotic interactions are supposed to be a key driver of biodiversity effects on ecosystem processes. One important interaction that has been gaining attention in the past years is the plant-microbe interaction, which has been shown to affect the interaction between plants and other organisms such as insects. This is mainly due to the fact that plant-associated microbes provide functional traits which are not coded on the plant’s genome but essential for plant fitness. Plant-associated microbiomes are either transferred from generation to generation via seeds or acquired from soil during plant growth. In the Jena Experiment, the structure and function of the soil microbiome depends on the plant diversity gradient. We hypothesize that selection in plant communities has led to shifts in the seed microbiome that can be complemented, but not completely substituted, by the soil microbiome. To test this hypothesis, we will investigate the role of soil and plant history on the associated soil, plant and seed microbiomes for the efficiency of plants to cope with biotic stressors as an example of a specific biodiversity dependent ecosystem function. We will address the following research questions: 1) How does plant- and soil history affect the plant microbiome? 2) What are key genes of the plantassociated microbiome driving the interaction between plants, microbes and invertebrates? 3) Which key genes are transferred via the seed microbiome to the next generation and which are provided by the soil as a result of different plant- and soil history? To address those questions we will characterize the seed microbiome of Plantago lanceolata, Trifolium pratense and Bromus erectus grown in monoculture or on 4-species plots in frame of the Field experiment. In order to characterize the trilateral interaction of plants, microbes and herbivores under different soil histories, we will participate in the Ecotron experiment and will analyze those treatments, which contain P. lanceolata and will be infested with herbivores. Additionally we will perform a Greenhouse experiment, where we will test additional herbivores and soil and plant history effects. Therefore, soils and seeds with monoculture history and 4-species mixture history will be reciprocally exchanged. We will combine metagenomic and metatranscriptomic approaches as well as quantitative PCR measurements to identify functional traits provided by the different seed microbes and those, which are expressed under biotic stress.