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Light quality modulates metabolic synchronization over the diel phases of crassulacean acid metabolism

Lookup NU author(s): Dr Johan Ceusters, Professor Anne Borland, Dr Tahar Taybi

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Temporal compartmentation of carboxylation processes is a defining feature of crassulacean acid metabolism and involves circadian control of key metabolic and transport steps that regulate the supply and demand for carbon over a 24 h cycle. Recent insights on the molecular workings of the circadian clock and its connection with environmental inputs raise new questions on the importance of light quality and, by analogy, certain photoreceptors for synchronizing the metabolic components of CAM. The present work tested the hypothesis that optimal coupling of stomatal conductance, net CO2 uptake, and the reciprocal turnover of carbohydrates and organic acids over the diel CAM cycle requires both blue and red light input signals. Contrasting monochromatic wavelengths of blue, green, and red light (i.e. 475, 530, 630 nm) with low fluence rates (10 mu mol m(-2) s(-1)) were administered for 16 hours each diel cycle for a total treatment time of 48 hours to the obligate CAM bromeliad, Aechmea 'Maya'. Of the light treatments imposed, low-fluence blue light was a key determinant in regulating stomatal responses, organic acid mobilization from the vacuole, and daytime decarboxylation. However, the reciprocal relationship between starch and organic acid turnover that is typical for CAM was uncoupled under low-fluence blue light. Under low-fluence red or green light, the diel turnover of storage carbohydrates was orchestrated in line with the requirements of CAM, but a consistent delay in acid consumption at dawn compared with plants under white or low-fluence blue light was noted. Consistent with the acknowledged influences of both red and blue light as input signals for the circadian clock, the data stress the importance of both red and blue-light signalling pathways for synchronizing the metabolic and physiological components of CAM over the day/night cycle.


Publication metadata

Author(s): Ceusters J, Borland AM, Taybi T, Frans M, Godts C, De Proft MP

Publication type: Article

Publication status: Published

Journal: Journal of Experimental Botany

Year: 2014

Volume: 65

Issue: 13

Pages: 3705-3714

Print publication date: 01/07/2014

Online publication date: 06/05/2014

Acceptance date: 25/03/2014

Date deposited: 01/10/2014

ISSN (print): 0022-0957

ISSN (electronic): 1460-2431

Publisher: Oxford University Press

URL: http://dx.doi.org/10.1093/jxb/eru185

DOI: 10.1093/jxb/eru185


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