Abstract
The thylakoid membrane is in a temperature-sensitive equilibrium that
shifts repeatedly during the life cycle in response to ambient
temperature or solar irradiance. Plants respond to seasonal temperature
by changing their thylakoid lipid composition, while a more rapid
mechanism for short-term heat exposure is required. The emission of the
small organic molecule isoprene has been postulated as one such possible
rapid mechanism. The protective mechanism of isoprene is not known, but
some plants emit isoprene during periods of high-temperature stress. In
this work, we investigate the dynamics and structure for lipids within a
thylakoid membrane at different temperatures and varied isoprene content
using classical molecular dynamics simulations. The results are compared
with experimental findings from across the literature for
temperature-dependent changes in the lipid composition and shape of
thylakoids. We find that the surface area, volume, and flexibility of
the membrane, as well as the lipid diffusion, increase with temperature,
while the membrane thickness decreases. Saturated thylakoid 34:3
glycolipids derived from eukaryotic synthesis pathways exhibit
significantly different dynamics than lipids from prokaryotic synthesis
paths, which could explain the upregulation of specific lipid synthesis
pathways at different temperatures. Increasing isoprene concentration
was not observed to have a significant thermoprotective effect on the
thylakoid membranes, and that isoprene readily permeated the membrane
models tested here.