Circadian Regulation of Plant Growth

Abstract

Circadian clocks generate 24 h biological rhythms that provide an adaptive advantage to organisms from all kingdoms. A simplified clock model comprises three main components: an input (e.g. light and temperature) that resets the oscillation daily; a central oscillator where several loops are connected by the intertwining of chromatin remodelling, transcriptional, and post‐translational mechanisms; and outputs including oscillating transcripts and/or proteins able to translate waving patterns into specific biological processes. Therefore, the clock maintains an anticipation mechanism controlling different aspects of the plant life cycle. From hypocotyl elongation (when seedlings grow through the soil reaching for light) to photosynthesis, stress responses and metabolism, the clock promotes plant fitness and an increase in biomass. Major developmental transitions are also under circadian regulation. Here, we will assess the impact of the circadian clock on plant growth (considering both elongation/expansion and biomass‐driven growth). We will address the regulation of cell growth and proliferation, starch metabolism, and protein translation, focusing especially in plants but providing some insights in other organisms. We expect that these findings will allow a broader understanding of the relevance of circadian‐regulated processes in providing organisms with the ability to adjust their growth and development to specific environmental conditions.

Sugars and the speed of life—Metabolic signals that determine plant growth, development and death

“…The circadian clock closely regulates the seasonal regulation of flowering time. This timekeeping mechanism integrates external (light, temperature) and internal (photosynthesis‐generated sugars) cues into specific waveforms of gene expression to regulate rhythmic biological processes (Henriques et al, 2018). Decreased sugar availability or seedling treatment with high doses of nicotinamide increased circadian period, indicating that metabolites and sugars can act as clock inputs (Haydon et al, 2013).…”

Circadian Rhythms in Plants

“…Plant growth is regulated by both environmental and internal cues, and therefore plant growth pathways are highly interconnected with the circadian clock regulatory network as well as with light-and temperature-signaling pathways (Nozue and Maloof 2006;Farré 2012;Kinmonth-Schultz et al 2013;Henriques et al 2018). The best-studied example of plant growth is the elongation of Arabidopsis hypocotyls, which is driven by anisotropic growth of cells formed during embryo development.…”

A framework of artificial light management for optimal plant development for smart greenhouse application

“…All living beings are embedded with a biological clock called the circadian clock that can synchronise the organism's biological functions with the 24-hour day cycles. In plants, the circadian system, which governs the optimal coordination of biological timing has been identified to be responsible for most of the plant development [32][33][34] such as flowering time, hypocotyl elongation, petal opening, roots growth etc. (see e.g.…”