A Novel Approach for Bypassing Photorespiration in C3 Plants: Partial Suppression of Photorespiration

Metabolism of glycolate via the photorespiratory pathway in C3 plants consumes not only ATP and reducing equivalents but results also in approximately 25% loss of the carbon from glycolate. a novel biochemical pathway for the metabolism of glycolate was established in the chloroplast of Arabidopsis thaliana plants. The pathway is derived from E. coli and converts the glycolate formed during photorespiration into glycerate. Three enzymatic activities are required: glycolate dehydrogenase (GDH), glyoxylate carboligase (GCL), and tartronic semialdehyde reductase (TSR). Transgenic A. thaliana plants containing the necessary genes for the novel pathway were generated. Variable amounts of foreign proteins as well as RNA were detected by Western blot and RT-PCR, respectively. Enzymatic assays showed that the proteins are active in planta. Biochemical, and physiological analyses were performed under ambient and enhanced photorespiratory conditions for evaluating the impact of the novel pathway in planta. it can be concluded that the expression of the novel pathway in C3 plant chloroplasts does not only result in a reduction of photorespiration but it also enhances plant growth.