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Review
. 2020 Oct 10:2020:3686791.
doi: 10.34133/2020/3686791. eCollection 2020.

Biosystems Design to Accelerate C3-to-CAM Progression

Guoliang Yuan  1   2 , Md Mahmudul Hassan  1   2   3 , Degao Liu  4 , Sung Don Lim  5 , Won Cheol Yim  6 , John C Cushman  6 , Kasey Markel  7 , Patrick M Shih  7   8 , Haiwei Lu  1 , David J Weston  1   2 , Jin-Gui Chen  1   2 , Timothy J Tschaplinski  1   2 , Gerald A Tuskan  1   2 , Xiaohan Yang  1   2
Affiliations
Review

Biosystems Design to Accelerate C3-to-CAM Progression

Guoliang Yuan et al. Biodes Res. .

Abstract

Global demand for food and bioenergy production has increased rapidly, while the area of arable land has been declining for decades due to damage caused by erosion, pollution, sea level rise, urban development, soil salinization, and water scarcity driven by global climate change. In order to overcome this conflict, there is an urgent need to adapt conventional agriculture to water-limited and hotter conditions with plant crop systems that display higher water-use efficiency (WUE). Crassulacean acid metabolism (CAM) species have substantially higher WUE than species performing C3 or C4 photosynthesis. CAM plants are derived from C3 photosynthesis ancestors. However, it is extremely unlikely that the C3 or C4 crop plants would evolve rapidly into CAM photosynthesis without human intervention. Currently, there is growing interest in improving WUE through transferring CAM into C3 crops. However, engineering a major metabolic plant pathway, like CAM, is challenging and requires a comprehensive deep understanding of the enzymatic reactions and regulatory networks in both C3 and CAM photosynthesis, as well as overcoming physiometabolic limitations such as diurnal stomatal regulation. Recent advances in CAM evolutionary genomics research, genome editing, and synthetic biology have increased the likelihood of successful acceleration of C3-to-CAM progression. Here, we first summarize the systems biology-level understanding of the molecular processes in the CAM pathway. Then, we review the principles of CAM engineering in an evolutionary context. Lastly, we discuss the technical approaches to accelerate the C3-to-CAM transition in plants using synthetic biology toolboxes.

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Conflict of interest statement

The authors declare that there is no conflict of interest regarding the publication of this article.

Figures

Figure 1
Figure 1
A simplified view of the crassulacean acid metabolism (CAM) photosynthetic pathway including key enzymes, regulatory proteins, and transporters.
Figure 2
Figure 2
Daytime and nighttime metabolism of organic acids in C3 and CAM plants. Arrow thickness denotes flux. Adapted from [67].
Figure 3
Figure 3
An evolution-based conceptual framework for crassulacean acid metabolism (CAM) engineering guidance. Hypothesis 1: CAM evolution followed a linear course leading from facultative CAM to strong constitutive CAM. Hypothesis 2: facultative and constitutive CAM evolved independently. The hypotheses were adapted from [18].
Figure 4
Figure 4
An inducible system for C3 crop in response to drought. (a) A CAM-on-demand system. (b) Sequence-specific transcriptional activation systems. (c) Boolean logic gates mediated CAM signaling systems. A value of 1 represents a true answer, and 0 represents a false answer.
Figure 5
Figure 5
An overview of synthetic biology-dependent crassulacean acid metabolism (CAM) engineering.
See this image and copyright information in PMC

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