摘要
The emergence of cell membrane is an essential step in the origin of life on earth.Cell membrane,a matrix with fatty acid derived lipids and proteins,separates the outside environment from enclosed cell internal.The composition
The emergence of cell membrane is an essential step in the origin of life on earth. Cell membrane, a matrix with fatty acid derived lipids and proteins, separates the outside envi- ronment from enclosed cell internal. The composition of membrane lipids largely determines biophysical properties of cell membrane, such as fluidity, permeability and deformability, which are essential for cellular processes. Temperature is an important environmental factor. Different species live in a dramatic variation of temperature conditions; for example, bacterial Thermus Aquaticus （in which the Taq DNA polymerase for PCR was first isolated） grows in hot springs while polar bears reside in arctic area. Individual cell or organism can adapt to a limited range of temperatures, which is also known as thermal tolerance. Temperature changes affect membrane fluidity. It has been known for a long time that bacteria respond to temperature changes by changing the fatty acid saturation of cell mem- brane through altering the expression of lipid desaturase, a phenomenon named homeoviscous adaptation （HVA） [1]. Later on, the phenomenon of HVA was found conserved in evolution [2]. In bacteria, a two-component regulatory sys- tem regulates lipid desaturase expression and mediates HVA. However, the two-component system genes are not found in eukaryotes and the molecular mechanism of HVA remains elusive in eukaryotes.
