Antimicrobial capacity of the freshwater planarians againstS. aureusis under the control of Timeless

Abstract

Planarians, which are non-parasitic flatworms, are highly resistant to bacterial infections. To better understand the mechanisms underlying this resistance, we investigated the role of the circadian machinery in the anti-bacterial response of the freshwater planarian Schmidtea mediterranea. We identified Smed-Tim from S. mediterranea as a homolog of the mammalian clock gene Tim. We showed via RNA interference that Smed-Tim is required for the anti-microbial activities of Schmidtea mediterranea against Staphylococcus aureus infection during the light/dark cycle. Indeed, S. aureus infection leads to the expression of Smed-Tim, which in turn promotes Smed-Traf6 and Smed-morn2, but not Smed-p38 MAPK expression, 2 master regulators of planarian anti-microbial responses.

The planarian Schmidtea mediterranea is a new model to study host-pathogen interactions during fungal infections

“…We speculate that the predicted pattern recognition receptor mediating the innate immune response against C. albicans is likely to be a CTL receptor, which will activate the SYK protein, and proceed to activate a complex that contains BCL and CARD proteins (Li et al, 2018;Maciel and Oviedo, 2018). This is also consistent with the idea that TAK1 is also active during this process, and interacts with P38 and other MAP kinase cascades that eventually end in the activation of the transcription factor NF-kβ (Arnold et al, 2016;Torre et al, 2017a;Tsoumtsa et al, 2017). Additional insights about the genetic network activated in the host will be obtained in future studies using genome-wide transcriptomic analyses during a time course of infection with C. albicans.…”

“…L. pneumophila, S. aureus, and M. tuberculosis, respectively) (Abnave et al, 2014). Thus, previous analyses of the planaria innate immune system during bacterial infection has provided useful information about host response strategies aimed at clearance of bacterial pathogens (Abnave and Ghigo, 2018;Abnave et al, 2014;Arnold et al, 2016;Gao et al, 2017;Hammoudi et al, 2018;Li et al, 2018;Lu et al, 2017;Pang et al, 2016;Torre et al, 2017a;Tsoumtsa et al, 2017Tsoumtsa et al, , 2018. Indeed, the function of the gene encoding the human homolog of Membrane Occupation and Recognition Nexus repeat containing-2 (MORN2) was unknown until a screen in planarians allowed for the identification of its function in phagocytosis and clearance of bacterial infections (Abnave et al, 2014).…”

“Candidatus Trichorickettsia mobilis”, a Rickettsiales bacterium, can be transiently transferred from the unicellular eukaryote Paramecium to the planarian Dugesia japonica

“…Thus, they may encounter in their environment a large variety of microbes (Petersen, 2014), including ciliates possibly hosting endosymbionts. Planarians have always been considered an important model for studying stem cells and regeneration (Rossi et al, 2008), but recently they became also important for studying the natural immunity system of Metazoa (Abnave et al, 2014;Conti, Abnave & Ghigo, 2014;Torre & Ghigo, 2015;Arnold et al, 2016;Torre et al, 2017;Tsoumtsa et al, 2017). Based on all these considerations, they appeared a suitable model for such experiments.…”

Outwitting planarian’s antibacterial defence mechanisms:Rickettsialesbacterial trans-infection fromParamecium multimicronucleatumto planarians

“…Thus, they may encounter in their environment a large variety of microbes [65], including ciliates possibly hosting endosymbionts. Planarians have always been considered an important model for studying stem cells and regeneration [66], but recently they became also important for studying the natural immunity system of Metazoa [67–72]. Based on all these considerations, they appeared a suitable model for such experiments.…”