Gene expression in lichen symbioses

• Applicant: Professorin Dr. Silke Werth
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405889398

Phenotypic plasticity, which is the ability of a single genotype to develop different phenotypes depending on the environment, may enable the persistence of populations in stressful environments. Variability in gene expression is an important type of phenotypic plasticity, with implications for the long-term survival of organisms in stressful environments. Understanding which factors influence gene expression plasticity is crucial to determine the potential susceptibility of species to future climate change. Lichens represent complex microbial consortia. An open question is which role lichen-associated bacteria and eukaryotes play in lichen stress responses. Based on the finding that certain transcripts and proteins of lichen-associated bacteria are involved in stress responses, it has been hypothesized that the lichen associated bacterial communities of lichens provide crucial physiological functions to lichen thalli, increasing fitness by enabling tolerance to biotic and abiotic stresses. However, the positive effects of the microbiome on lichen fitness under stressful conditions remains to be demonstrated. Lichenicolous fungi are commensals or biotrophic parasites growing on lichens. Some lichenicolous fungi have important fitness consequences by reducing a lichen’s amount of carbon-based secondary compounds, rendering the lichen vulnerable to attack by microbes, other lichenicolous fungi, or herbivores. Lichenicolous fungi obtain the carbon necessary for their growth from the lichen, which may aggravate stress conditions for the lichen. By impacting thallus integrity and tapping into the overall carbon pool, lichenicolous fungi could aggravate stress responses and cause corresponding changes in mycobiont and/or photobiont gene expression, but this phenomenon has not yet received attention. The main goal of this project is to understand the role of biotic factors on gene expression of L. pulmonaria and its green-algal photobiont when it is exposed to thermal stress and benign conditions. The specific objectives are: 1) Evaluate the relative effects of physiological acclimatization and genetic variation on the expression of mycobiont and photobiont genes under thermal treatments for thalli differing in biotic interactions, 2) Determine the effect of species interactions on gene expression, testing for possible stress-mediating effects of lichen-associated microbial communities by quantifying lichen temperature-treatment related gene expression after experimental manipulation of the lichen microbiome, and 3) Quantify possible negative fitness consequences of lichenicolous fungi for their lichen hosts by analyzing gene expression in response to temperature treatments including stressful conditions.

• DFG Programme: Research Grants