The Role of the Hypoxia-Inducible Factor in the Euprymma scolopes, V. fischeri Endosymbiosis
Mortensen, Jordan Plaisier
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The Hawaiian bobtail squid, Euprymma scolopes has been well characterized due to its unique endosymbiotic relationship with Vibrio fischeri, a bioluminescent bacterium. V. fischeri live within the light organ of the squid and provides camouflage by giving off light which resembles moonlight and renders the nocturnal squid difficult to detect from below. This relationship is highly evolved and the onset of symbiosis triggers many developmental changes within the squid. As with all morphological changes the mechanism by which they occur must be regulated on the molecular level. One potential transcription factor that may be involved in these morphological changes is the hypoxia inducible factor (HIF). HIF has been shown to be activated by low oxygen conditions in a wide array of organisms. Colonization by the bacterium creates a hypoxic environment within the light organ of the squid. This may activate HIF and be a mechanism for colonization induced adaptation. The purpose of this study was to investigate a possible role of HIF in the onset of symbiosis. This was done by examining the effects of HIF specific inhibitors on the luminescence of V. fischeri colonized juvenile E. scolopes. Scintillation counter experiments demonstrated that inhibition of HIF leads to a decreased luminescence in symbiotic squid during the first 20 hours of colonization. Luminescence and growth rate of the bacterium were measured in the presence and absence of inhibitor, and no significant difference was detected. This indicates that the inhibitors did not directly impact the bioluminescence reaction or the growth rate of V. fischeri, suggesting that HIF may be involved in the molecular response of the squid to the hypoxic environment within the colonized light organ.