Facultative crassulacean acid metabolism in a C-3-C-4 intermediate

Winter, Klaus, Sage, Rowan F., Edwards, Erika J., Virgo, Aurelio, and Holtum, Joseph A.M. (2019) Facultative crassulacean acid metabolism in a C-3-C-4 intermediate. Journal of Experimental Botany, 70 (22). pp. 6571-6579.

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Abstract

The Portulacaceae enable the study of the evolutionary relationship between C-4 and crassulacean acid metabolism (CAM) photosynthesis. Shoots of well-watered plants of the C-3-C-4 intermediate species Portulaca cryptopetala Speg. exhibit net uptake of CO2 solely during the light. CO2 fixation is primarily via the C-3 pathway as indicated by a strong stimulation of CO2 uptake when shoots were provided with air containing 2% O-2. When plants were subjected to water stress, daytime CO2 uptake was reduced and CAM-type net CO2 uptake in the dark occurred. This was accompanied by nocturnal accumulation of acid in both leaves and stems, also a defining characteristic of CAM. Following rewatering, net CO2 uptake in the dark ceased in shoots, as did nocturnal acidification of the leaves and stems. With this unequivocal demonstration of stress-related reversible, i.e. facultative, induction of CAM, P. cryptopetala becomes the first C-3-C-4 intermediate species reported to exhibit CAM. Portulaca molokiniensis Hobdy, a C-4 species, also exhibited CAM only when subjected to water stress. Facultative CAM has now been demonstrated in all investigated species of Portulaca, which are well sampled from across the phylogeny. This strongly suggests that in Portulaca, a lineage in which species engage predominately in C-4 photosynthesis, facultative CAM is ancestral to C-4. In a broader context, it has now been demonstrated that CAM can co-exist in leaves that exhibit any of the other types of photosynthesis known in terrestrial plants: C-3, C-4 and C-3-C-4 intermediate.

Item ID: 61608
Item Type: Article (Research - C1)
ISSN: 1460-2431
Keywords: C-4 photosynthesis, crassulacean acid metabolism, Portulaca cryptopetala, Portulaca molokiniensis, Portulacaceae
Copyright Information: © The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Experimental Biology. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
Funders: Australian Research Council (ARC), US National Science Foundation (NSF), Smithsonian Tropical Research Institute
Projects and Grants: ARC DP160100098, NSF DEB-125901
Date Deposited: 29 Jan 2020 07:30
FoR Codes: 06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060705 Plant Physiology @ 100%
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