Overexpressing the H-protein of the glycine cleavage system increases biomass yield in glasshouse and field-grown transgenic tobacco plants

Authors: South, Paul; LOPEZ-CALGANO, PATRICIA - University Of Essex; RAINES, CHRISTINE - University Of Essex; FISK, STUART - University Of Essex; BULL, SIMON - University Of Essex

Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2018
Publication Date: 5/31/2018
Citation: South, P.F., Lopez-Calgano, P., Raines, C., Fisk, S., Bull, S. 2018. Overexpressing the H-protein of the glycine cleavage system increases biomass yield in glasshouse and field-grown transgenic tobacco plants. Plant Biotechnology Journal. https://doi.org/10.1111/pbi.12953.
DOI: https://doi.org/10.1111/pbi.12953

Interpretive Summary: C3 crops such as wheat, rice, and soybean undergo a process called photorespiration. Depending on growing temperatures photorespiration can reduce crop yields by 20-50%. To reduce crop losses due to photorespiration we engineered the model crop tobacco with an faster photorespiration pathway.. Top performing plant lines were able to increase productivity and increase biomass yields by >17% in field trials. These results provide compelling proof-of-concept that engineering alternative glycolate metabolic pathways into crops while inhibiting glycolate export into the native pathway can drive significant increases in C3 crop yield.

Technical Abstract: Photorespiration is essential for C3 plants, enabling oxygenic photosynthesis through thescavenging of 2-phosphoglycolate. Previous studies have demonstrated that overexpression ofthe L- and H-proteins of the photorespiratory glycine cleavage system results in an increase inphotosynthesis and growth inArabidopsis thaliana. Here, we present evidence that undercontrolled environment conditions an increase in biomass is evident in tobacco plantsoverexpressing the H-protein. Importantly, the work in this paper provides a clear demonstrationof the potential of this manipulation in tobacco grown in field conditions, in two separateseasons. We also demonstrate the importance of targeted overexpression of the H-protein usingthe leaf-specific promoter ST-LS1. Although increases in the H-protein driven by this promoterhave a positive impact on biomass, higher levels of overexpression of this protein driven by theconstitutive CaMV 35S promoter result in a reduction in the growth of the plants. Furthermore inthese constitutive overexpressor plants, carbon allocation between soluble carbohydrates andstarch is altered, as is the protein lipoylation of the enzymes pyruvate dehydrogenase and alpha-ketoglutarate complexes. Our data provide a clear demonstration of the positive effects ofoverexpression of the H-protein to improve yield under field conditions.