Differential expression of heat shock protein 70 in relation to stress type in the flatworm Schmidtea polychroa
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Most heat shock proteins help to cope with stress in organisms ranging from bacteria to vertebrates. Many stress types acting on the intensity of intracellular protein can induce expression of heat shock proteins. Here, we studied changes in expression level of heat shock protein 70 (Hsp70), one of the best investigated stress proteins, in response to five potential stress factors in the planarian flatworm Schmidtea polychroa: (1) homogenized planarian tissue, which releases an alarm substance that signals predation injury, (2) physical damage by puncturing, (3) a simulation of ecological competition by adding a mixture of naturally co-occurring species: one Dendrocoelum and two Polycelis flatworms, one Asellus water louse and one leech, and (4) magnesium chloride, which inhibits regeneration ability. We found that alarm substance (1), physical harm (2), and magnesium chloride (4) led to increased expression of Hsp70, while interspecific competition (3) did not result in elevated Hsp70 expression. There was no difference between the experimental negative control and two temporal controls immediately after collection and just before the experiment. Results show that Schmidtea polychroa is not sensitive to sampling and lab maintenance. However, planarian homogenate, magnesium chloride and physical harm all caused Hsp70-inducing stress. We conclude that Hsp70 quantification is appropriate to study the current stress level in planaria in response to specific conditions.
KeywordsFreshwater ecology Platyhelminthes Biomarker Stress response Regeneration Western blotting
We thank Milosz Olczak and Gregor Schulte for collecting flatworms and Nadine Timmermeyer for the assistance during the experiment. We are grateful to Rebecca Schulte and Nadine Timmermeyer for fruitful discussions and valuable comments to improve previous versions of this manuscript. This study was supported by a grant from the German Science Foundation (DFG) no. MI 482/11 and the Volkswagen Foundation (Initiative Curriculum Evolutionary Biology: Tübingen in Evolution, Evolution in Tübingen).
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