Introduction of Exogenous Glycolate Catabolic Pathway Can Strongly Enhances Photosynthesis and Biomass Yield of Cucumber Grown in a Low-CO2 Environment

Abstract

Carbon dioxide (CO 2 ) is very important for photosynthesis of green plants. CO 2 concentration in the atmosphere is relatively stable, but it drops sharply after sunrise due to the tightness of the greenhouse and the absorption of CO 2 by vegetable crops. Vegetables in greenhouses are chronically CO 2 starved. To investigate the feasibility of using genetic engineering to improve the photosynthesis and yield of greenhouse cucumber in a low CO 2 environment, five genes encoding glyoxylate carboligase (GCL), tartronic semialdehyde reductase (TSR), and glycolate dehydrogenase (GlcDH) in the glycolate catabolic pathway of Escherichia coli were partially or completely introduced into cucumber chloroplast. Both partial pathway by introducing GlcDH and full pathway expressing lines exhibited higher photosynthetic efficiency and biomass yield than wild-type (WT) controls in low CO 2 environments. Expression of partial pathway by introducing GlcDH increased net photosynthesis by 14.9% and biomass yield by 44.9%, whereas the expression of the full pathway increased seed yield by 33.4% and biomass yield by 59.0%. Photosynthesis, fluorescence parameters, and enzymatic measurements confirmed that the introduction of glycolate catabolic pathway increased the activity of photosynthetic carbon assimilation-related enzymes and reduced the activity of photorespiration-related enzymes in cucumber, thereby promoting the operation of Calvin cycle and resulting in higher net photosynthetic rate even in low CO 2 environments. This increase shows an improvement in the efficiency of the operation of the photosynthetic loop. However, the utilization of cucumber of low concentration CO 2 was not alleviated. This study demonstrated the feasibility of introducing the pathway of exogenous glycolate catabolic pathway to improve the photosynthetic and bio-yield of cucumber in a low CO 2 environment. These findings are of great significance for high photosynthetic efficiency breeding of greenhouse cucumber.

Two glyoxylate reductase isoforms are functionally redundant but required under high photorespiration conditions in rice

“…4 a). However, when the photorespiration was promoted by low CO 2 concentration and continuous light [ 27 , 28 ], the OsGR1/OsGR2 double mutants showed stunted growth (Fig. 4 b, Additional file 4 ).…”

“…Pre-germinated rice seeds were normally grown in KimuraB complete nutrient solution [45] under greenhouse condition (14 h light/10 h dark, average temperature of 30/25°C (light/dark), relative humidity 60-80% and average light intensity of 600 μmol m − 2 s − 1 ). In order to promote photorespiration, the rice plants were cultivated in enclosed glass tubes (21 cm height, 3.0 cm diameter) under continuous light, and then the CO 2 levels in the tubes decreased rapidly, facilitating the flux of the photorespiration [27,28].…”

Biosynthetic approaches to efficient assimilation of CO2via photorespiration modification in plant chassis

“…1. Among the reported photorespiratory bypass pathways implemented into plants, E. coli- originated glyoxylate oxidation catalysis has been extensively tested ( Kebeish et al, 2007 ; Dalal et al, 2015 ; South et al, 2019 ; Chen et al, 2019 ; Wang et al, 2019 ; Nayak et al, 2022 ; Zhang et al, 2022 ). Glycolate is converted into glyoxylate by glycolate dehydrogenase (GDH) or glycolate oxidase (GLO), followed by the generation of tartronic semialdehyde and CO 2 from two molecules of glyoxylate catalyzed by glyoxylate carboligase (GCL).…”

Wasteful, essential, evolutionary stepping stone? The multiple personalities of the photorespiratory pathway

“…If these three changes would come into effect, they ought to directly link the reactions catalysed by PGLP and GLYK, bridging all other reactions of the photorespiratory pathway. This strategy was adopted by Dalal et al () for Camelina sativa , Ahmad et al (; using cyanobacterial genes) for potato, Chen et al () for cucumber and South et al () for tobacco. The second approach attempted to stably introduce a related pathway into the peroxisome of tobacco in order to convert glyoxylate to hydroxypyruvate, avoiding the release of CO 2 and ammonia by the GCS, but failed to overexpress one of the required enzymes, hydroxypyruvate isomerase (Carvalho et al , ).…”