Winter, Klaus, and Holtum, Joseph A.M. (2024) Shifting photosynthesis between the fast and slow lane: Facultative CAM and water-deficit stress. Journal of Plant Physiology, 294. 154185.

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Abstract

Five decades ago, the first report of a shift from C3 to CAM (crassulacean acid metabolism) photosynthesis following the imposition of stress was published in this journal. The annual, Mesembryanthemum crystallinum (Aizoaceae), was shown to be a C3 plant when grown under non-saline conditions, and a CAM plant when exposed to high soil salinity. This observation of environmentally triggered CAM eventually led to the introduction of the term facultative CAM, which categorises CAM that is induced or upregulated in response to water-deficit stress and is lost or downregulated when the stress is removed. Reversibility of C3–to–CAM shifts distinguishes stress-driven facultative-CAM responses from purely ontogenetic increases of CAM activity. We briefly review how the understanding of facultative CAM has developed, evaluate the current state of knowledge, and highlight questions of continuing interest. We demonstrate that the long-lived leaves of a perennial facultative-CAM arborescent species, Clusia pratensis, can repeatedly switch between C3 and CAM in response to multiple wet–dry–wet cycles. Undoubtedly, this is a dedicated response to environment, independent of ontogeny. We highlight the potential for engineering facultative CAM into C3 crops to provide a flexible capacity for drought tolerance.

Item ID:	86022
Item Type:	Article (Research - C1)
ISSN:	1618-1328
Copyright Information:	© 2024 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Date Deposited:	02 Jul 2025 00:58
FoR Codes:	31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310802 Plant biochemistry @ 100%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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