Abstract
The lipid matrix in cell membranes is a dynamic, bidimensional array of amphipathic molecules exhibiting mesomorphism, which contributes to the membrane fluidity changes in response to temperature fluctuation. As sessile organisms, plants must rapidly and accurately respond to environmental thermal variations. However, mechanisms underlying temperature perception in plants are poorly understood. We studied the thermal plasticity of membrane fluidity using three fluorescent probes across a temperature range of −5 to 41 °C in isolated microsomal fraction (MF), vacuolar membrane (VM), and plasma membrane (PM) vesicles from Arabidopsis plants. Results showed that PM were highly fluid and exhibited more phase transitions and hysteresis, while VM and MF lacked such attributes. These findings suggest that PM is an important cell hub with the capacity to rapidly undergo fluidity modifications in response to small changes of temperatures in ranges spanning those experienced in natural habitats. PM fluidity behaves as an ideal temperature detector: it is always present, covers the whole cell, responds quickly and with sensitivity to temperature variations, functions with a cell free-energy cost, and it is physically connected with potential thermal signal transducers to elicit a cell response. It is an optimal alternative for temperature detection selected for the plant kingdom.
Highlights
Cell membranes have a lipid matrix that behaves as a bi-dimensional organized solution in which lipid molecules exhibit the intrinsic property of mesomorphism
We found that plasma membrane (PM) was highly fluid compared to microsomal fraction (MF) and vacuolar membrane (VM), during both heating and cooling across 23 consecutive measurements in a temperature range from −5 to 41 ◦C
MF and VM showed lines with none or one phase transitions during heating or cooling in the presence of DPH, TMA-DPH, or PA. These results are in agreement with previous reports, in which VM isolated from Kalanchoë daigremontiana subjected to a gradual rise in temperature from −5 to 40 ◦C showed an increase in fluidity measured with DPH or β-py-C10-HPC, no changes in slope were observed [35]
Summary
Cell membranes have a lipid matrix that behaves as a bi-dimensional organized solution in which lipid molecules exhibit the intrinsic property of mesomorphism. This is conferred by the amphipathic nature of lipids and their weak intermolecular interactions. A fluid state facilitates lateral movement of lipids, adequate conformational changes of integral proteins, and protein–protein and protein–lipid interactions [6]. These phenomena are vital for solute transport, signal transduction, cell communication, cell division, and many other cellular processes
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