Homeocurvature: A new dimension of membrane adaptation to extreme environments.

Adaptation to abiotic factors is essential for life's radiation across the planet. Lipids, particularly sensitive to pressure and temperature (P and T), play a critical role in biochemical adaptation. In oceanic depths, lower temperatures and increasing hydrostatic pressure influence lipid packing. The prevailing model for lipid response to P and T has been homeoviscosity, regulating membrane viscosity. However, our recent systematic analysis of lipid adaptation in ctenophores revealed an alternative homeocurvature model influenced by the spontaneous curvature of phospholipids. This model highlights pressure as a stronger modulator of lipid curvature than membrane fluidity, which is particularly relevant in deep-sea environments. This review aims to enhance understanding of lipidome responses by synthesizing the challenges posed by extreme P and T. We explore the interplay between homeocurvature and homeoviscosity, illustrating the unexpected genesis of the homeocurvature model through chemical and biophysical trends. We apply both models to four published lipidomic datasets from diverse marine taxa, proposing that broader environmental sampling is vital for assessing existing models and discovering new ones. Understanding membrane responses to environmental factors informs the function of cell membranes broadly and helps predict the evolutionary and ecological impacts of global change.