Mid-Term Report Summary - RESIST (Resistance systems and population structure of parasites)
The project aims at understanding the specific interactions between hosts and parasites; that is, the fact that only some parasite strains (here, genotypic variants of the same trypanosomatid parasite, C. bombi) are able to infect a given host type (different genotypic backgrounds of the bumblebee, B. terrestris) - and, vice versa, that host types vary in their susceptibility against a given parasite strain. In particular, the project investigates whether differential gene expression, rather than differences in the genes themselves, in combination with synergism rule specific interactions.
Work done in this project has now shown that genes are indeed differentially expressed according to who (which parasite strain) infects whom (which host type), and that sequence differences in the respective genes are negligible instead. Such a gene expression interaction system provides defences against parasitic infections, which are presumably very versatile. A core set of the responsible genes includes those coding for anti-microbial peptides (AMPs), which are naturally occurring antibiotics found in most organisms, including insects. The project has now shown that some of these AMPs are in fact those whose expression is typically associated with the specific host-parasite interaction. During this work, several steps had been taken to establish, verify, and reduce the large number of expressed genes to a practical set. In the second part of the project, the parasite was experimentally evolved in culture. At the same time, several AMPs from B. terrestris were synthesized in the lab. First tests showed that single AMPs alone do not have a significant effect, but that their synergistic interaction is the key for a successful action against microbes. Hence, the results indicated that differential expression of genes leads to different "cocktails" of AMPs that, by synergistic action, are specifically effective against a given infection. This general idea will now be tested with synthesized AMPs and with the now established tool of experimental evolution.
Taken together, the results obtained so far support the working hypothesis that an alternative defence system based on differential gene expression and synergism among major effectors, such as anti-microbial peptides, can provide a very adaptable solution to highly variable parasites in natural populations.
Work done in this project has now shown that genes are indeed differentially expressed according to who (which parasite strain) infects whom (which host type), and that sequence differences in the respective genes are negligible instead. Such a gene expression interaction system provides defences against parasitic infections, which are presumably very versatile. A core set of the responsible genes includes those coding for anti-microbial peptides (AMPs), which are naturally occurring antibiotics found in most organisms, including insects. The project has now shown that some of these AMPs are in fact those whose expression is typically associated with the specific host-parasite interaction. During this work, several steps had been taken to establish, verify, and reduce the large number of expressed genes to a practical set. In the second part of the project, the parasite was experimentally evolved in culture. At the same time, several AMPs from B. terrestris were synthesized in the lab. First tests showed that single AMPs alone do not have a significant effect, but that their synergistic interaction is the key for a successful action against microbes. Hence, the results indicated that differential expression of genes leads to different "cocktails" of AMPs that, by synergistic action, are specifically effective against a given infection. This general idea will now be tested with synthesized AMPs and with the now established tool of experimental evolution.
Taken together, the results obtained so far support the working hypothesis that an alternative defence system based on differential gene expression and synergism among major effectors, such as anti-microbial peptides, can provide a very adaptable solution to highly variable parasites in natural populations.