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RESEARCH ARTICLE SUMMARY PLANT SCIENCE Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field Paul F. South, Amanda P. Cavanagh, Helen W. Liu, Donald R. Ort* INTRODUCTION: Meeting food demands for the growing global human population requires improving crop productivity, and large gains are possible through enhancing photosynthetic efficiency. Photosynthesis requires the carbox- ylation of ribulose-1,5-bisphosphate (RuBP) by buld 15 binhohoto pohodo altered photorespiratory pathways within the chloroplast have shown promising results, in- cluding increased photosynthetic rates and plant size. RATIONALE: To determine if alternative pho- minotom no uld affectiunlu im enzymes in the alternative pathway designs were directed to the chloroplast. RNA inter- ference (RNAI) was also used to down-regulate a native chloroplast glycolate transporter in the photorespiratory pathway, thereby limiting metabolite flux through the native pathway. The three pathways were introduced with and without the trans- porter RNAi construct into tobacco, which is an ideal model field crop be- cause it is easily trans- formed, has a short life cycle, produces large quan- tities of seed, and develops a robust canopy similar to that of other field crops. ON OUR WEBSITE Read the full article at http://dx.doi. org/10.1126/ science.aat9077 RESULTS: Using a synthetic biology approach to vary promoter gene combinations, we gen- erated a total of 17 construct designs of the three pathways with and without the trans- porter RNAi construct. Initial screens for pho- bu alte atin thumu fanatic

RESEARCH ARTICLE SUMMARY PLANT SCIENCE Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field Paul F. South, Amanda P. Cavanagh, Helen W. Liu, Donald R. Ort* INTRODUCTION: Meeting food demands for the growing global human population requires improving crop productivity, and large gains are possible through enhancing photosynthetic efficiency. Photosynthesis requires the carbox- ylation of ribulose-1,5-bisphosphate (RuBP) by buld 15 binhohoto pohodo altered photorespiratory pathways within the chloroplast have shown promising results, in- cluding increased photosynthetic rates and plant size. RATIONALE: To determine if alternative pho- minotom no uld affectiunlu im enzymes in the alternative pathway designs were directed to the chloroplast. RNA inter- ference (RNAI) was also used to down-regulate a native chloroplast glycolate transporter in the photorespiratory pathway, thereby limiting metabolite flux through the native pathway. The three pathways were introduced with and without the trans- porter RNAi construct into tobacco, which is an ideal model field crop be- cause it is easily trans- formed, has a short life cycle, produces large quan- tities of seed, and develops a robust canopy similar to that of other field crops. ON OUR WEBSITE Read the full article at http://dx.doi. org/10.1126/ science.aat9077 RESULTS: Using a synthetic biology approach to vary promoter gene combinations, we gen- erated a total of 17 construct designs of the three pathways with and without the trans- porter RNAi construct. Initial screens for pho- bu alte atin thumu fanatic

Biochemistry
Biochemistry
6th Edition
ISBN:9781305577206
Author:Reginald H. Garrett, Charles M. Grisham
Publisher:Reginald H. Garrett, Charles M. Grisham
Chapter21: Photosynthesis
Section: Chapter Questions
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Analyze and summarize the important findings

RESEARCH ARTICLE SUMMARY PLANT SCIENCE Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field Paul F. South, Amanda P. Cavanagh, Helen W. Liu, Donald R. Ort* altered photorespiratory pathways within the chloroplast have shown promising results, in- cluding increased photosynthetic rates and plant size. INTRODUCTION: Meeting food demands for the growing global human population requires improving crop productivity, and large gains are possible through enhancing photosynthetic efficiency. Photosynthesis requires the carbox- ylation of ribulose-1,5-bisphosphate (RuBP) by ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO), but photorespiration occurs in most plants such as soybean, rice, and wheat (known as C, crops) when RuBisCO oxygenates RuBP instead, requiring costly processing of toxic byproducts such as glycolate. Photorespiration can reduce C, crop photosynthetic efficiency by 20 to 50%. Although various strategies exist for lowering the costs of photorespiration, chamber- and greenhouse-grown plants with RATIONALE: To determine if alternative pho- torespiratory pathways could effectively im- prove Cs field crop productivity, we tested the performance of three alternative photorespi- ratory pathways in field-grown tobacco. One pathway used five genes from the Escherichia coli glycolate oxidation pathway; a second path- way used glycolate oxidase and malate syn- thase from plants and catalase from E. coli; and the third pathway used plant malate synthase and a green algal glycolate dehydrogenase. All Chloroplast Peroxisome Glycerate Glycerate Hydroxypyruvate Glycolate Glyoxylate Glycine Tartronic- semialdehyde CO₂ Glyoxylate 2-P-Glycolate Glycolate H₂0₂ Glyoxylate Glyoxylate NH, Malate Pyruvate Mitochondria Alternate pathways Alternative photorespiratory pathways in tobacco. Three alternative pathways [1 (red). 2 (dark blue), and 3(light blue)] introduced into tobacco chloroplasts for more efficient recycling of glycolate. RNAi suppresses the native glycolate/glycerate transporter PLGG1 to prevent glycolate from leaving the chloroplast and entering the native pathway (gray). 3-P-Glycerate RuBisCO RuBP 10014 Acetyl-CoA Glycine Serine CO₂ Serine enzymes in the alternative pathway designs were directed to the chloroplast. RNA inter- ference (RNAI) was also used to down-regulate a native chloroplast glycolate transporter in the photorespiratory pathway, thereby limiting metabolite flux through the native pathway. The three pathways were introduced with and without the trans- porter RNAi construct into tobacco, which is an ideal model field crop be- cause it is easily trans- formed, has a short life ON OUR WEBSITE Read the full article at http://dx.doi. org/10.1126/ science.aat9077 cycle, produces large quan- tities of seed, and develops a robust canopy similar to that of other field crops. RESULTS: Using a synthetic biology approach to vary promoter gene combinations, we gen- erated a total of 17 construct designs of the three pathways with and without the trans- porter RNAi construct. Initial screens for pho- toprotection by alternative pathway function under high-photorespiratory stress conditions identified three to five independent transfor- mants of each design for further analysis. Gene and protein expression analyses confirmed ex- pression of the introduced genes and suppres- sion of the native transporter in RNAi plants. In greenhouse screens, pathway 1 increased biomass by nearly 13%. Pathway 2 showed no benefit compared to wild type. Introduction of pathway 3 increased biomass by 18% without RNAi and 24% with RNAi, which were con- sistent with changes in photorespiratory me- tabolism and higher photosynthetic rates. Ultimately, field testing across two different growing seasons showed significant increases in biomass of pathway 3 plants with RNAi compared to WT of 20 % in 2016 ( P = 0.04) and by 24% in 2017 (P = 0.018). In addition, this pathway increased the light-use efficiency of photosynthesis by 17% in the field. CONCLUSION: Engineering more efficient photorespiratory pathways into tobacco while inhibiting the native pathway markedly in- creased both photosynthetic efficiency and vegetative biomass. We are optimistic that sim- ilar gains may be achieved and translated into increased yield in C, grain crops because pho- torespiration is common to all C, plants and higher photosynthetic rates under elevated CO₂, which suppresses photorespiration and in- creases harvestable yield in C, crops. The list of author affiliations is available in the full article online. *Corresponding author. Email: d-ort@illinois.edu This is an open-access article distributed under the terms of the Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cite this article as P. F. South et al, Science 363, east9077 (2019). DOI: 10.1126/science.ast9077
Transcribed Image Text:RESEARCH ARTICLE SUMMARY PLANT SCIENCE Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field Paul F. South, Amanda P. Cavanagh, Helen W. Liu, Donald R. Ort* altered photorespiratory pathways within the chloroplast have shown promising results, in- cluding increased photosynthetic rates and plant size. INTRODUCTION: Meeting food demands for the growing global human population requires improving crop productivity, and large gains are possible through enhancing photosynthetic efficiency. Photosynthesis requires the carbox- ylation of ribulose-1,5-bisphosphate (RuBP) by ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO), but photorespiration occurs in most plants such as soybean, rice, and wheat (known as C, crops) when RuBisCO oxygenates RuBP instead, requiring costly processing of toxic byproducts such as glycolate. Photorespiration can reduce C, crop photosynthetic efficiency by 20 to 50%. Although various strategies exist for lowering the costs of photorespiration, chamber- and greenhouse-grown plants with RATIONALE: To determine if alternative pho- torespiratory pathways could effectively im- prove Cs field crop productivity, we tested the performance of three alternative photorespi- ratory pathways in field-grown tobacco. One pathway used five genes from the Escherichia coli glycolate oxidation pathway; a second path- way used glycolate oxidase and malate syn- thase from plants and catalase from E. coli; and the third pathway used plant malate synthase and a green algal glycolate dehydrogenase. All Chloroplast Peroxisome Glycerate Glycerate Hydroxypyruvate Glycolate Glyoxylate Glycine Tartronic- semialdehyde CO₂ Glyoxylate 2-P-Glycolate Glycolate H₂0₂ Glyoxylate Glyoxylate NH, Malate Pyruvate Mitochondria Alternate pathways Alternative photorespiratory pathways in tobacco. Three alternative pathways [1 (red). 2 (dark blue), and 3(light blue)] introduced into tobacco chloroplasts for more efficient recycling of glycolate. RNAi suppresses the native glycolate/glycerate transporter PLGG1 to prevent glycolate from leaving the chloroplast and entering the native pathway (gray). 3-P-Glycerate RuBisCO RuBP 10014 Acetyl-CoA Glycine Serine CO₂ Serine enzymes in the alternative pathway designs were directed to the chloroplast. RNA inter- ference (RNAI) was also used to down-regulate a native chloroplast glycolate transporter in the photorespiratory pathway, thereby limiting metabolite flux through the native pathway. The three pathways were introduced with and without the trans- porter RNAi construct into tobacco, which is an ideal model field crop be- cause it is easily trans- formed, has a short life ON OUR WEBSITE Read the full article at http://dx.doi. org/10.1126/ science.aat9077 cycle, produces large quan- tities of seed, and develops a robust canopy similar to that of other field crops. RESULTS: Using a synthetic biology approach to vary promoter gene combinations, we gen- erated a total of 17 construct designs of the three pathways with and without the trans- porter RNAi construct. Initial screens for pho- toprotection by alternative pathway function under high-photorespiratory stress conditions identified three to five independent transfor- mants of each design for further analysis. Gene and protein expression analyses confirmed ex- pression of the introduced genes and suppres- sion of the native transporter in RNAi plants. In greenhouse screens, pathway 1 increased biomass by nearly 13%. Pathway 2 showed no benefit compared to wild type. Introduction of pathway 3 increased biomass by 18% without RNAi and 24% with RNAi, which were con- sistent with changes in photorespiratory me- tabolism and higher photosynthetic rates. Ultimately, field testing across two different growing seasons showed significant increases in biomass of pathway 3 plants with RNAi compared to WT of 20 % in 2016 ( P = 0.04) and by 24% in 2017 (P = 0.018). In addition, this pathway increased the light-use efficiency of photosynthesis by 17% in the field. CONCLUSION: Engineering more efficient photorespiratory pathways into tobacco while inhibiting the native pathway markedly in- creased both photosynthetic efficiency and vegetative biomass. We are optimistic that sim- ilar gains may be achieved and translated into increased yield in C, grain crops because pho- torespiration is common to all C, plants and higher photosynthetic rates under elevated CO₂, which suppresses photorespiration and in- creases harvestable yield in C, crops. The list of author affiliations is available in the full article online. *Corresponding author. Email: d-ort@illinois.edu This is an open-access article distributed under the terms of the Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cite this article as P. F. South et al, Science 363, east9077 (2019). DOI: 10.1126/science.ast9077
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