Development of a toolbox to dissect host-endosymbiont interactions and protein trafficking in the trypanosomatid Angomonas deanei

Abstract

BackgroundBacterial endosymbionts are found across the eukaryotic kingdom and profoundly impacted eukaryote evolution. In many endosymbiotic associations with vertically inherited symbionts, highly complementary metabolic functions encoded by host and endosymbiont genomes indicate integration of metabolic processes between the partner organisms. While endosymbionts were initially expected to exchange only metabolites with their hosts, recent evidence has demonstrated that also host-encoded proteins can be targeted to the bacterial symbionts in various endosymbiotic systems. These proteins seem to participate in regulating symbiont growth and physiology. However, mechanisms required for protein targeting and the specific endosymbiont targets of these trafficked proteins are currently unexplored owing to a lack of molecular tools that enable functional studies of endosymbiotic systems.ResultsHere we show that the trypanosomatid Angomonas deanei, which harbors a β-proteobacterial endosymbiont, is readily amenable to genetic manipulation. Its rapid growth, availability of full genome and transcriptome sequences, ease of transfection, and high frequency of homologous recombination have allowed us to stably integrate transgenes into the A. deanei nuclear genome, efficiently generate null mutants, and elucidate protein localization by heterologous expression of a fluorescent protein fused to various putative targeting signals. Combining these novel tools with proteomic analysis was key for demonstrating the routing of a host-encoded protein to the endosymbiont, suggesting the existence of a specific endosymbiont-sorting machinery in A. deanei.ConclusionsAfter previous reports from plants, insects, and a cercozoan amoeba we found here that also in A. deanei, i.e. a member of a fourth eukaryotic supergroup, host-encoded proteins can be routed to the bacterial endosymbiont. This finding adds further evidence to our view that the targeting of host proteins is a general strategy of eukaryotes to gain control over and interact with a bacterial endosymbiont. The molecular resources reported here establish A. deanei as a time and cost efficient reference system that allows for a rigorous dissection of host-symbiont interactions that have been, and are still being shaped over evolutionary time. We expect this system to greatly enhance our understanding of the biology of endosymbiosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0820-z) contains supplementary material, which is available to authorized users.

Evolution of host support for two ancient bacterial symbionts with differentially degraded genomes in a leafhopper host

“…Protein import of more than 200 genes has been identified from the single-celled eukaryote P. chromatophora (80, 100). Protein translocation to the cellular matrix of bacterial symbiont was similarly demonstrated in the trypanosomatid Angomonas deanei (103). Furthermore, in the insect symbiosis between the pea aphid and Buchnera , it was also shown that a host encoded protein ( rlpA4 ) is imported into the bacterial symbiont’s cytosol (104).…”

Multiple origins of interdependent endosymbiotic complexes in a genus of cicadas

“…Complexes. Similar to mitochondria and chloroplasts, endosymbiotic bacteria that have undergone high levels of genome reduction are thought to rely on host proteins to function (35)(36)(37)(38). The smallest Hodgkinia genome from Tettigades spp., TETCHI5, encodes only 16 proteins and 5 RNAs, on par with a typical insect mitochondrial genome (13 protein-coding, 2 rRNA, and 22 tRNA genes) (13).…”

Acquisition of Uropygial Gland Microbiome by Hoopoe Nestlings

“…Hosts provide beneficial microorganisms with physical support and resources for growth, which could also be exploited by undesired parasitic-symbiont partners (e.g. [5]). Even though the risk of exploitation of host resources by non-mutualistic symbionts is considered a destabilizing force of mutualistic relationships (reviewed in [6]), mutualisms with bacteria are ubiquitous and remain during evolutionary time [4] indicating the existence of mechanisms preventing parasitic exploitation.…”