Assessing microbe mediated adaptation to different food sources via comparative symbiomics of lower termites

• Applicant: Dr. Fabian Staubach
• Subject Area: Evolution, Anthropology
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270882710

Most studies today that aim at understanding how organisms adapt to their environment focus on the host organism alone. Only recently it is becoming clearer that microorganisms serve as a vast reservoir of genes that can facilitate adaptation of a host. If a microorganism carries a gene with a function that is beneficial to the host, hosts that can recognize and associate with this microorganism have a fitness benefit. Some of the molecules and pathways by which beneficial bacteria are recognized are known. Interestingly, these pathways also play a role in the recognition of pathogens. However, some of the ecologically and economically most relevant symbioses are symbioses not of bacteria, but of eukaryotic microbes with multicellular hosts. Here, recognition molecules and pathways are largely unknown. Studying the interaction of lower termites and their beneficial eukaryotic gut symbionts, on which they depend to digest their food substrate, will allow us to independently test the emerging paradigm that the recognition of beneficial microbes relies on similar mechanisms as pathogen recognition. In order to identify termite and protist genes involved in host-microbe interaction, we will compare the transcriptomes of termites with and without their protist gut microbiota (GM) using illumina HiSeq based RNAseq. Furthermore, we will apply this approach to three termite species adapted to wood dwelling, which is the ancestral life style, and one species that adapted to forage soil to test if the GM plays a role in substrate adaptation. If the GM is important for adaptation to soil foraging, we expect that positive selection acted on termite genetic variants that favor the association with microbes providing a fitness benefit on soil. In response, the expression or coding sequence of genes involved in interaction with the GM changes when termites adapt to soil foraging. In order to identify adaptive changes in gene expression, we will search these comparative transcriptomics data from four termite species for changes in gene expression that are specific to soil foragers and affect genes involved in the interaction with the GM. The RNAseq data will be used at the same time for McDonald-Kreitman-tests of selection on the coding sequence of genes involved in host-symbiont interaction. Microbial metatranscriptomes will inform us about genes that are expressed exclusively by the GM of soil foragers and could be relevant for substrate adaptation. Termite candidate genes that show both, evidence for an involvement in interaction with the GM and adaptive change, will be functionally tested for their effect on the termite species specific GM via RNAi. The species specific GM will be profiled using 16S and 18S rRNA gene sequencing. With this comprehensive approach we will identify genes involved in the recognition of eukaryotic symbionts and analyze their adaptive significance.

• DFG Programme: Research Grants
• International Connection: Saudi Arabia
• Co-Investigator: Professor Christian Voolstra, Ph.D.