Cellular adaptation to dehydration stress : molecular adaptations for dehydration tolerance in the African clawed frog, Xenopus laevis

SMAD Transcription Factor Expression in Anoxia-Tolerant Trachemys Scripta Elegans and Dehydration-Tolerant Xenopus Laevis: A Comparative Study

“…Indeed, FoxO1 protein levels increased significantly in the hepatocyte nucleus and binding to DNA to affect the transcription of important redox enzymes. MnSOD protein and transcript levels were raised 1.4-and 1.5-fold, respectively, in liver while catalase protein was upregulated in both muscle and liver, with liver also displaying a greater than twofold elevation in transcript levels compared to control frogs (Malik, 2009). This evidence confirms the important role that SMAD transcription factors play in switching on the oxidative stress response in muscle and liver.…”

“…c-Fos was upregulated in X. laevis liver under both dehydration conditions (about a 1.6-fold increase in protein levels compared to CXL,Figure 3.13), whereas muscle showed a similar pattern with a 1.5-fold increase during MD, but a more dramatic upturn during HD (nearly a three-fold increase compared to control,Figure 3.15). c-Jun was upregulated during high dehydration in both liver and muscle in about the same proportions (about a 1.5-fold increase compared to CXL;Malik, 2009). Both of these DNA binding proteins are merely part of the Fos and Jun subgroups, respectively, of transcription factors that form AP-1 dimers when activated.Their activation is reliant on many forms of physiological and pathological stimuli and in the case of X. laevis that stimulus or stress is dehydration(Shaulian and Karin, 2001).…”

“…FOXOs are a set of proteins that are known to play a major role in regulating the expression of antioxidant genes in X. laevis while the frog undergoes seasonal dehydration (Malik andStorey, 2009, 2011). Indeed, FoxO1 protein levels increased significantly in the hepatocyte nucleus and binding to DNA to affect the transcription of important redox enzymes.…”

“…Also known as the platanna, X. laevis is native to sub-Saharan Africa (Sudan, Nigeria, and South Africa) (Figure 1.4B), as are all species of the Xenopus genus, and has developed many morphological features to alleviate stresses that arise from the seasonally arid environment -mainly to deal with the stress of dehydration. The frog has been shown to withstand water loss of 30-35% of its total body water (Malik, 2009;Romspert 1976).…”

Anuran adaptations to climatic stress : immune responses and the SMAD family in the wood frog, Rana sylvatica, and the African clawed frog, Xenopus laevis

“…Evidence of the potential role of TGF-P 1 signaling is the activation of MAPK family members from both the extracellular signal-regulated kinases (ERK) pathway and the c-Jun N-terminal kinase (INK) pathway inX. laevis skeletal muscle during dehydration (Malik & Storey, 2009;Malik, 2009). This prompts future work looking at the expression of myogenesis targets in the myocyte enhancer factor-2 (MEF2) family, for which SMADs are a co-modulator of transcription (Quinn et al, 2001).…”