Expression pattern of the novel freeze-responsive genes li16, fr10 and fr47 in the wood frog, Rana sylvatica
The ability of the wood frog (Rana sylvatica) to freeze up to 65% of its total body water allows it to endure subzero temperatures encountered during winter. To survive the stresses associated with freezing, frogs have evolved multiple molecular adaptations including expression of three novel genes: li16, fr10 and fr47. All three genes were found to be freeze responsive in a tissue-dependent manner. They also all respond to anoxia and dehydration stresses, suggesting that the transcription of these genes is triggered by the low oxygen conditions common to all three stresses. Protein levels were elevated after freezing for Li16; however FR10 and FR47 generally showed no change or a decrease in protein after freezing. Transcripts of all three genes were also detected during tadpole development, indicating a possible additional role for metamorphosis. Finally,bioinformatic analysis of their sequences provided insight into functional motifs and potential regulatory sites on the proteins.