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Lookup NU author(s): Natalia Hurtado Castaño, Emeritus Professor Jerry Barnes, Emerita Professor Anne Borland
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© The Author(s) 2023.• Background and Aims Crassulacean acid metabolism (CAM) is a specialized type of photosynthesis characterized by a diel pattern of stomatal opening at night and closure during the day, which increases water-use efficiency. Starch degradation is a key regulator of CAM, providing phosphoenolpyruvate as a substrate in the mesophyll for nocturnal assimilation of CO2. Growing recognition of a key role for starch degradation in C3 photosynthesis guard cells for mediating daytime stomatal opening presents the possibility that starch degradation might also impact CAM by regulating the provision of energy and osmolytes to increase guard cell turgor and drive stomatal opening at night. In this study, we tested the hypothesis that the timing of diel starch turnover in CAM guard cells has been reprogrammed during evolution to enable nocturnal stomatal opening and daytime closure. • Methods Biochemical and genetic characterization of wild-type and starch-deficient RNAi lines of Kalanchoë fedtschenkoi with reduced activity of plastidic phosphoglucomutase (PGM) constituted a preliminary approach for the understanding of starch metabolism and its implications for stomatal regulation in CAM plants. • Key Results Starch deficiency reduced nocturnal net CO2 uptake but had negligible impact on nocturnal stomatal opening. In contrast, daytime stomatal closure was reduced in magnitude and duration in the starch-deficient rPGM RNAi lines, and their stomata were unable to remain closed in response to elevated concentrations of atmospheric CO2 administered during the day. Curtailed daytime stomatal closure was linked to higher soluble sugar contents in the epidermis and mesophyll. • Conclusions Nocturnal stomatal opening is not reliant upon starch degradation, but starch biosynthesis is an important sink for carbohydrates, ensuring daytime stomatal closure in this CAM species.
Author(s): Hurtado-Castano N, Atkins E, Barnes J, Boxall SF, Dever LV, Knerova J, Hartwell J, Cushman JC, Borland AM
Publication type: Article
Publication status: Published
Journal: Annals of Botany
Year: 2023
Volume: 132
Issue: 4
Pages: 881-894
Print publication date: 20/09/2023
Online publication date: 20/01/2023
Acceptance date: 19/01/2023
Date deposited: 05/02/2024
ISSN (print): 0305-7364
ISSN (electronic): 1095-8290
Publisher: Oxford University Press
URL: https://doi.org/10.1093/aob/mcad017
DOI: 10.1093/aob/mcad017
PubMed id: 36661206
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