Researchers at Johns Hopkins have identified that a protein ‘rhodopsin’ present in the eye and responsible for the perception of light, is also vital for sensing temperature. The study was supported by the National Institute of General Medical Sciences
Professor of biological chemistry at Johns Hopkins, Craig Montell stated that for decades it was believed that the protein functioned exclusively as a light receptor until a study on fly larvae revealed that other organisms use rhodopsin to differentiate differences in temperature.
The protein was identified while investigating the process, which leads to the activation of TRPA1, a temperature-sensor protein. The Hopkins team discovered that fly larvae detect slight changes in temperatures, essential to their survival, using the TRPA1. They found that unlike other TRP channels, TRPA1 did not respond to temperature changes in the comfortable range which lies between 18°C- 24°C. Further investigation involving 75 larvae placed on a plate with 2 temperature zones revealed that the larvae lacking the rhodopsin protein were unable to detect temperature changes, similar to larvae lacking TRPA1. The larvae with the rhodopsin gene chose the comfortable temperature range over extreme temperatures.
With genetical and behavioral studies, which supported the finding, it was established that rhodopsin is essential for thermo-sensation. Professor Montell explained that rhodopsin was activated by temperature, which further activates TRPA1. Additionally, the temperature-sensing function of rhodopsin is independent of light. This was confirmed by a similar test on fly larvae, which were subjected to different temperatures in a dark box and were able to choose their preferred temperature.
The report titled ‘Function of rhodopsin in temperature discrimination in Drosophila’ was published in the March 11 edition of Science.
Source: http://www.neuroscience.jhu.edu