Entrainment of Arabidopsis roots to the light:dark cycle by light piping

• Published in: Plant, cell and environment Vol. 41; no. 8; pp. 1742 - 1748
• Main Author: Nimmo, Hugh G.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-08-2018
• Subjects: Arabidopsis; Arabidopsis - metabolism; Arabidopsis - physiology; Arabidopsis - radiation effects; Arabidopsis thaliana; Biological clocks; circadian clock; Circadian Rhythm - radiation effects; Circadian rhythms; Darkness; Entrainment; Exposure; Light; light piping; light quality; Photoperiod; Piping; Plant Roots - metabolism; Plant Roots - physiology; Plant Roots - radiation effects; Plant Shoots - metabolism; Plant Shoots - physiology; Plant Shoots - radiation effects; Plant tissues; Roots; Shoots; Arabidopsis thaliana; light quality; roots; circadian clock; entrainment; light piping
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13137

Correct operation of the plant circadian clock is crucial for optimal growth and development. Recent evidence has shown that the plant clock is tissue specific and potentially hierarchical, implying that there are signalling mechanisms that can synchronise the clock in different tissues. Here, I have addressed the mechanism that allows the shoot and root clocks to be synchronised in light:dark cycles but not in continuous light. Luciferase imaging data from 2 different Arabidopsis accessions with 2 different markers show that the period of the root clock is much less sensitive to blue light than to red light. Decapitated roots were imaged either in darkness or with the top section of root tissue exposed to light. Exposure to red light reduced the period of the root tissue maintained in darkness, whereas exposure to blue light did not. The data indicate that light can be piped through root tissue to affect the circadian period of tissue in darkness. I propose that the synchronisation of shoots and roots in light:dark cycles is achieved by light piping from shoots to roots.
The plant circadian clock is tissue‐specific and potentially hierarchical, implying that there are signalling mechanisms that can synchronise the clock in different tissues. This work addresses the mechanism that allows the shoot and root clocks to be synchronised in light:dark cycles but not in continuous light. The data indicate that light can be piped through root tissue to affect the circadian period of tissue in darkness. This emphasizes the physiological importance of light piping in plant biology.