Bacterial Form II Rubisco can support wild-type growth and productivity in Solanum tuberosum cv. Desiree potato under elevated CO2

The last decade has seen significant advances in the development of approaches for improving both the light harvesting and carbon fixation pathways of photosynthesis by nuclear transformation, many involving multigene synthetic biology approaches. As efforts to replicate these accomplishments from tobacco into crops gather momentum, similar diversification is needed in the range of transgenic options available, including capabilities to modify crop photosynthesis by chloroplast transformation. To address this need, here we describe the first transplastomic modification of photosynthesis in a crop by replacing the native Rubisco in potato with the faster, but lower CO2-affinity and poorer CO2/O-2 specificity Rubisco from the bacterium Rhodospirillum rubrum. High level production of R. rubrum Rubisco in the potRr genotype (8 to 10 mu mol catalytic sites m(2)) allowed it to attain wild-type levels of productivity, including tuber yield, in air containing 0.5% (v/v) CO2. Under controlled environment growth at 25 degrees C and 350 mu mol photons m(2) PAR, the productivity and leaf biochemistry of wild-type potato at 0.06%, 0.5%, or 1.5% (v/v) CO2 and potRr at 0.5% or 1.5% (v/v) CO2 were largely indistinguishable. These findings suggest that increasing the scope for enhancing productivity gains in potato by improving photosynthate production will necessitate improvement to its sink-potential, consistent with current evidence productivity gains by eCO(2) fertilization for this crop hit a ceiling around 560 to 600 ppm CO2.

Automated summary

Significant advances have been made in the past decade in improving light harvesting and carbon fixation pathways of photosynthesis through nuclear transformation. This study demonstrates the successful modification of photosynthesis in potato by replacing the native Rubisco with a faster Rubisco from Rhodospirillum rubrum, leading to increased productivity.