Osmotic induction of stress-responsive gene expression in the lobster Homarus americanus

The American lobster, Homarus americanus, encounters osmotic stress throughout its life cycle. To understand the molecular basis of osmotic stress responses in vivo, we used homologous cDNA probes to characterize the mRNA patterns of lobster HSP70 (=70-kDa heat-shock protein), HSP90 (=90-kDa heat-shock protein), and polyubiquitin during hypo- and hyper-osmotic stress in abdominal muscle and hepatopancreas (a digestive tissue) at 30, 60, and 120 min of osmotic stress. Hypo- and hyper-osmotic stress significantly increased the levels of the mRNAs encoding HSP70 and HSP90 in abdominal muscle. Hyper-osmotic stress increased HSP90 mRNA levels in hepatopancreas, but hypo-osmotic stress did not. Both abdominal muscle and hepatopancreas exhibited significant changes in polyubiquitin gene expression during osmotic stress. In abdominal muscle, polyubiquitin mRNA levels increased during both hypo- and hyper-osmotic stress. Hepatopancreas, however, showed a significant elevation in polyubiquitin mRNA only during hypo-osmotic stress.