Abstract
Light is a critical environmental stimulus for plants, serving as an energy source via photosynthesis and a signal for developmental programming. Plants perceive light through various light-responsive proteins, termed photoreceptors. Phytochromes are red-light photoreceptors that are highly conserved across kingdoms. In the model plant Arabidopsis thaliana, phytochrome B serves as a light and thermal sensor, mediating physiological processes such as seedling germination and establishment, hypocotyl growth, chlorophyll biogenesis, and flowering. In response to red light, phytochromes convert to a biologically active form, translocating from the cytoplasm into the nucleus and further compartmentalizes into subnuclear compartments termed photobodies. PhyB photobodies regulate phytochrome-mediated signaling and physiological outputs. However, photobody function, composition, and biogenesis remain undefined since their discovery. Based on photobody cellular dynamics and the properties of internal components, photobodies have been suggested to undergo liquid-liquid phase separation, a process by which some membraneless compartments form. Here, we explore photobodies as environmental sensors, examine the role of their protein constituents, and outline the biophysical perspective that photobodies may be undergoing liquid-liquid phase separation. Understanding the molecular, cellular, and biophysical processes that shape how plants perceive light will help in engineering improved sunlight capture and fitness of important crops.
Highlights
Light is the most critical environmental stimulus for all plant development, serving as the energy source for photosynthesis and as an environmental cue to regulate growth and development
PhyA is mainly responsible for sensing and responding to far-red light, in addition to red light, whereas phyB-E are responsible for photomorphogenesis in response to red light and foliar shade (Whitelam et al, 1992; McCormac et al, 1993; Nagatani et al, 1993; Parks and Quail, 1993; Whitelam et al, 1993; Reed et al, 1994; Paik and Huq, 2019)
We explore the biological significance of photobodies in Arabidopsis thaliana, how photobodies contribute to signaling in fluctuating environments, protein components that promote photobody formation, photobody biogenesis, how liquid– liquid phase separation (LLPS) may underlie the biophysical mechanism of assembly, and photobody functions
Summary
Light is the most critical environmental stimulus for all plant development, serving as the energy source for photosynthesis and as an environmental cue to regulate growth and development. Increasing the intensity of red light, which stabilizes the Pfr form, promotes the formation of large photobodies (Chen et al, 2003; Van Buskirk et al, 2012). Further work found that all members of the phy family formed nuclear bodies at differing rates in response to red and white light (Kircher et al, 2002), suggesting that photobody localization was a regulated process.
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