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

Preempting Racial Inequities in Lung Cancer Screening

Lung cancer is the leading cause of cancer death in the U.S., and Black patients experience higher lung cancer incidence and mortality than White patients.1 Lung cancer screening facilitates diagnoses at earlier, more treatable stages. In 2011, low-dose computed tomography (LDCT) showed a relative reduction in lung cancer-specific mortality by 20% in the National Lung Screening Trial (NLST), a multisite randomized controlled trial comparing LDCT and chest radiography for lung cancer screening (N=53,454).2 NLST results indicated that LDCT reduces lung cancer mortality in all racial groups, but a stronger effect was observed among Black patients.3 Therefore, LDCT has potential to mitigate racial disparities in lung cancer mortality. However, this potential can only be achieved with equitable LDCT utilization