Phytochrome A Mediates the Disassembly of Processing Bodies in Far-Red Light.

Philipp Schwenk,Andreas Hiltbrunner

doi:10.3389/fpls.2022.828529

Abstract

Phytochromes are red- and far-red light receptors that control the growth and development of plants, enabling them to respond adequately to changing light conditions. It has been shown that halted mRNAs stored in RNA granules called processing bodies are released upon light perception and contribute to the adaptation to the light environment. However, the photophysiological background of this process is largely unknown. We found that light of different wavelengths can trigger the disassembly of processing bodies in a dose- and time-dependent manner. We show that phytochromes control this process in red- and far-red light and that cytoplasmic phytochrome A is sufficient and necessary for the far-red light-induced disassembly of processing bodies. This adds a novel, unexpected cytoplasmic function to the processes controlled by phytochrome A. Overall, our findings suggest a role of phytochromes in the control of translationally halted mRNAs that are stored in processing bodies. We expect our findings to facilitate understanding of how light and environmental cues control the assembly and disassembly of processing bodies, which could have broader implications for the regulation of non-membranous organelles in general.

Highlights

It was shown that a mutation in COP1, cop1-6, leads to decreased p-body numbers in darkness. This is in line with the light-independent activation of light signalling in the cop1-6 mutant (Ma et al, 2002). These results indicate an involvement of the phytochrome signalling system in the disassembly of p-bodies in response to light
Supporting this notion, we found that supplementing the growth medium with sucrose does not have any effect on the number of p-bodies (Supplementary Figure 1)
Light signalling mediated by phytochromes has been researched for more than 70 years, and still our knowledge of these processes is incomplete

Summary

Introduction

Throughout their life cycle, plants are subject to constantly changing environmental conditions at the place where they germinated. In order to cope with fluctuations in the surrounding, plants sense and integrate environmental cues and react with a high level of plasticity to adapt their growth and development (Chevin and Lande, 2015). This integration happens at different levels, including gene expression (Peschke and Kretsch, 2011), translation, and degradation of proteins (Wu et al, 2019), as well as modifications of mechanical properties of cell walls (Falcioni et al, 2020). The formation and disassembly of processing bodies (p-bodies), a sub-class of RNA granules, is a mechanism to store translationally halted mRNAs and release them in response to specific conditions that has recently gained attention in different model organisms and contexts (Decker and Parker, 2012; Wang et al, 2018; Jang et al, 2019)

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