Biosystems Design to Accelerate C3-to-CAM Progression.

Md Mahmudul Hassan,John C Cushman,Sung Don Lim,David J Weston,Timothy J Tschaplinski,Xiaohan Yang,Won Cheol Yim,Kasey Markel,Patrick M Shih,Haiwei Lu,Gerald A Tuskan,Jin-Gui Chen,Degao Liu,Guoliang Yuan

doi:10.34133/2020/3686791

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.

Highlights

The global population has quadrupled over the past 100 years and will continue to increase in the 21st century [1]
One of the most direct approaches is engineering crassulacean acid metabolism (CAM) into C3 crops to enhance water-use efficiency (WUE) in plants [9] thereby allowing such crops to be grown on marginal lands with reduced fresh water inputs
We developed a de novo multiplex CRISPR activation (CRISPRa) system that can simultaneously perturbate the expression of eight genes in A. thaliana (Yuan et al, unpublished data)

Summary

Introduction

The global population has quadrupled over the past 100 years and will continue to increase in the 21st century [1]. Ongoing and projected climate changes are (1) affecting many sectors important to society, including human health, agricultural sustainability, water supply, energy security, and food supply and (2) becoming increasingly disruptive in the coming decades [2,3,4]. These opposing trends are threatening our global food and energy security [5]. In CAM plants, stomata close during part or all of the day to reduce water loss, and the CO2 is released from the malate generated during the first CO2-fixing stage, resulting in enhanced plant WUE in comparison with C3 or C4 plants. We integrate the capabilities of gene editing and synthetic biology for CAM engineering, with a focus on building a CAM-ondemand system to increase plant resistance to episodic or seasonal drought stress

A Systems Biology-Level Understanding of CAM Photosynthesis

The Progress in the Understanding of CAM Evolution

Evaluation

Conclusion and Perspectives

Disclosure

Conflicts of Interest