U.S.-France Cooperative Research: Transcriptional and Posttranscriptional Regulation of the Sodium Pump

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Many coastal habitats include estuaries in which the mixing of fresh water and seawater establishes a salinity gradient affected by tidal cycles and rainfall. A few species of plants and animals have evolved physiological mechanisms that permit reproductive success in such stressful environments. Among these are aquatic crustaceans like the shore crab Pachygrapsus marmoratus and others such as the green crab Carcinus maenas and the Asian crab Hemigrapsus sanguineus that are highly invasive in ecosystems where they lack natural predators. We hypothesize that these animals resist changes in salinity by regulating (1) the expression of specific genes and (2) the function of proteins encoded by those genes. We propose to examine this hypothesis in the shore crab Pachygrapsus marmoratus, a highly successful species in intertidal estuarine environments. Like many euryhaline crabs, this species is capable of taking up salt from dilute salinities, using the sodium pump to energize the process. However, P. marmoratus is also capable of salt excretion in environments more concentrated than normal seawater. Our aim is to delineate the steps leading to differences in sodium pump gene expression, with emphasis on neurohormonal factors and cell signaling pathways. The proposed research will lead to enhanced training opportunities for both the host (Mount Desert Island Biological Laboratory) and counterpart (Universite Montpellier II, France). The French lab will learn additional molecular techniques while the host lab will gain expertise in electrophysiology and gill perfusion. An important part of the proposed research is the involvement of undergraduates, to be recruited from Maine colleges, who will collaborate in the proposed research in both countries.