6 research outputs found
Chloroplasts in plant cells show active glassy behavior under low-light conditions
Plants have developed intricate mechanisms to adapt to changing light
conditions. Besides photo- and helio- tropism -- the differential growth
towards light and the diurnal motion with respect to sunlight -- chloroplast
motion acts as a fast mechanism to change the intracellular structure of leaf
cells. While chloroplasts move towards the sides of the plant cell to avoid
strong light, they accumulate and spread out into a layer on the bottom of the
cell at low light to increase the light absorption efficiency. Although the
motion of chloroplasts has been studied for over a century, the collective
organelle-motion leading to light adapting self-organized structures remains
elusive. Here we study the active motion of chloroplasts under dim light
conditions, leading to an accumulation in a densely packed quasi-2D layer. We
observe burst-like re-arrangements and show that these dynamics resemble
colloidal systems close to the glass transition by tracking individual
chloroplasts. Furthermore, we provide a minimal mathematical model to uncover
relevant system parameters controlling the stability of the dense configuration
of chloroplasts. Our study suggests that the meta-stable caging close to the
glass-transition in the chloroplast mono-layer serves a physiological
relevance. Chloroplasts remain in a spread-out configuration to increase the
light uptake, but can easily fluidize when the activity is increased to
efficiently re-arrange the structure towards an avoidance state. Our research
opens new questions about the role that dynamical phase transitions could play
in self-organized intracellular responses of plant cells towards environmental
cues
Ultrasensitive and robust mechanoluminescent living composites
Mechanosensing, the transduction of extracellular mechanical stimuli into intracellular biochemical signals, is a fundamental property of living cells. However, endowing synthetic materials with mechanosensing capabilities comparable to biological levels is challenging. Here, we developed ultrasensitive and robust mechanolumines-cent living composites using hydrogels embedded with dinoflagellates, unicellular microalgae with a near-instantaneous and ultrasensitive bioluminescent response to mechanical stress. Not only did embedded dinoflagellates retain their intrinsic mechanoluminescence, but with hydrophobic coatings, living composites had a lifetime of ~5 months under harsh conditions with minimal maintenance. We 3D-printed living composites into large-scale mechanoluminescent structures with high spatial resolution, and we also enhanced their mechanical properties with double-network hydrogels. We propose a counterpart mathematical model that captured experimental mechanoluminescent observations to predict mechanoluminescence based on deformation and applied stress. We also demonstrated the use of the mechanosensing composites for biomimetic soft actuators that emitted colored light upon magnetic actuation. These mechanosensing composites have substantial potential in biohybrid sensors and robotics.</p