Climate change or no climate change, organisms respond to changes in temperature on a regular basis. Heat shock proteins are notorious for being up-regulated during periods of temperature shock. Plants and animals time their reproduction to seasonal variation in temperatures. We determine our wardrobe choices (at least partially) based on the temperature outside. Internal clocks are partially set by daily changes in temperature. But how is temperature sensed? There isn't a photon or chemical odor to be received.
Kumar and Wigge have uncovered that
chromatin changes mediated by the alternative histone H2A.Z are responsible for sensing temperature in Arabidopsis (a member of the cabbage or mustard family). Plants without H2A.Z mimic plants grown in warm temperatures - e.g. faster development, fewer leaves and shorter time to flowering. The idea is that H2A.Z histones are incorporated into the DNA in the promoters of temperature sensitive genes (such as heat shock proteins). The H2A.Z histones change the way the DNA is wrapped to prevent transcription or interfere with repressors. As the temperature increases, H2A.Z releases the DNA allowing for activator or repressor transcription factors to bind and/or work to rapidly change gene expression.
With the threat of global warming looming in the not so distant future, understanding the mechanisms by which organisms sense and respond to temperature is increasingly important. Kumar and Wigge (2010) found that yeast also use H2A.Z to sense temperature. It will be interesting to see if animals also use H2A.Z in this fashion. H2A.Z is highly conserved across metazoa, however there could be small changes in the protein that shed light on differential responses to temperature. When do H2A.Z leave the DNA? 1 degree change, 10 degree change? Also, perturbation of H2A.Z would reveal the species-specific molecular consequences of increasing temperature. How does this pathway feed into developmental gene regulatory networks?
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