Molecular regulation of mutualism establishment

1 PhD project proposal in the IPP summer call 2019

Scientific Background

Symbiotic associations between different organisms represent important driving forces of evolutionary adaptation. In particular, genes involved in the recognition and control of pathogens or mutualists are among the most rapidly evolving genes in eukaryotes, due to coevolutionary dynamics among the interacting partners. However, how the regulation of such genes changes during evolution and how this affects symbioses remains poorly understood. To address these questions, a group of darkling beetles (Tenebrionidae, Lagriinae) presents particularly suitable model systems, because they engage in a dynamic protective symbiosis (Flórez et al. 2017). Female beetles carry multiple strains of Burkholderia gladioli bacteria in specialized organs and transmit them to their offspring via the egg surface, as well as horizontally via the host plant (Flórez & Kaltenpoth 2017, Flórez et al. 2018). On the egg surface, the symbionts provide protection against detrimental fungi by producing various secondary metabolites with antimicrobial activity (Flórez et al. 2017, 2018). Later, the bacteria invade the embryo and colonize the beetle larva. Given the dynamic nature of the Lagria-Burkholderia symbiosis, the host needs to control symbiont invasion to ensure specificity.

PhD project proposal: Evolution of molecular mechanisms regulating mutualism establishment

To gain insights into how molecular mechanisms governing mutualism evolve on the genetic, gene regulatory, and epigenetic level, the project will investigate the defensive Lagria-Burkholderia symbiosis to elucidate (i) the gene regulatory mechanisms underlying the establishment of mutualism during host development in two congeneric beetle species, (ii) the specificity of recognition and control systems, and (iii) epigenetic priming of the offspring for symbiosis establishment. We maintain two beetle species and in vitro cultures of their symbionts in the lab and can experimentally manipulate the beetles’ symbiont infection status (Flórez et al. 2017). In addition, a draft genome of Lagria villosa is already available. The project will use a combination of multiple approaches, including experimental manipulation of the symbiosis, RNAseq for characterizing gene expression profiles during symbiosis establishment, monitoring of symbiont colonization success by microscopy, qPCR, and FISH, as well as silencing of candidate host genes by RNA interference (RNAi).

Publications relevant to the project

Flórez LV, Biedermann PHW, Engl T and Kaltenpoth M (2015) Defensive symbioses of animals with prokaryotic and eukaryotic microorganisms. Natural Product Reports 32 (7): 904-936.

Flórez LV, Scherlach K, Gaube P, Ross C, Sitte E, Hermes C, Rodrigues A, Hertweck C and Kaltenpoth M (2017) Antibiotic-producing symbionts dynamically transition between plant pathogenicity and insect-defensive mutualism. Nature Communications 8, 15172.

Flórez LV and Kaltenpoth M (2017) Symbiont dynamics and strain diversity in the defensive mutualism between Lagria beetles and Burkholderia. Environmental Microbiology 19, 3674-3688.

Flórez LV, Scherlach K, Miller I, Rodrigues A, Kwan J, Hertweck C and Kaltenpoth M (2018) An antifungal polyketide associated with horizontally acquired genes supports symbiont-mediated defense in Lagria villosa beetles. Nature Communications 9: 2478.

Contact Details

Prof. Martin Kaltenpoth

Prof. Martin Kaltenpoth
Department for Evolutionary Ecology
Johannes Gutenberg University Mainz

Tel: +49 (0) 6131-39 24411