Could ROS signals drive tissue-specific clocks?

Abstract

Circadian clocks have emerged to tune the physiology of organisms to periodic changes in the environment in a dynamic fashion. Negative implications of circadian disruptions in humans, animals and plants have encouraged extensive studies of clock-controlled biological processes in various model species. Recently, it has been shown that the transcription-dependent and -independent biological oscillators are largely driven by cellular oxidative cycles that are intrinsically linked with metabolism. Essentially, the clock is viewed as an integrated network that encompasses cytosolic, genetic and metabolic dimensions. Furthermore, in multicellular organisms, the clock network is organized in a tissue-specific manner. Here we discuss questions that remain unanswered: How do these dimensions communicate with each other and how do tissue-specific clocks exchange temporal information within multicellular organisms?

Figure 1. H₂O₂ might synchronize the Arabidopsis clock in the dark. The gene expression data shown were extracted from microarray experiments performed on seedlings grown for 7 d in the light or grown on 5 mM H₂O₂ in the dark as compared with dark grown seedlings. Among the core clock genes, CCA1 and LHY are modulated in a similar level by H₂O₂ as by light, while TOC1 is only modulated by light. H vs D: H₂O₂ treatment vs. dark grown seedlings. L vs D: Light vs. dark grown seedlings. AGI codes: CCA1 (At2g46830); LHY (At1g01060); JMJD5 (At3g20810); TIC (At3g222380); TOC1 (At5g61380); RVE8 (At3g09600); PRR7 (At5g02810); ELF4 (At2g40080); PIF4 (At2g43010); PIF5 (At3g59060).