Effects of co-overproduction of Rubisco and chloroplast glyceraldehyde-3-phosphate dehydrogenase on photosynthesis in rice

The capacity for regeneration of the substrate for Rubisco, ribulose 1,5-bisphosphate (RuBP), is one of the candidates for the bottleneck in photosynthesis in transgenic rice plants with overproduction of Rubisco. As the overproduction of chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was suggested to slightly enhance RuBP regeneration capacity, transgenic rice plants with co-overproduction of Rubisco and GAPDH were generated to improve photosynthesis. The amount of Rubisco increased by 8% to 18%, whereas GAPDH activity increased to 2.1- to 3.2-fold that of the wild-type. However, the rate of CO2 assimilation did not increase under conditions of high irradiance and different [CO2] partial pressures. The possibility that photosynthesis in the co-overproduced plants was co-limited by Rubisco, GAPDH, and other unknown factors is discussed.

Automated summary

The overproduction of Rubisco and GAPDH in transgenic rice plants increased their respective activities, but did not lead to an increase in CO2 assimilation rate under high irradiance and different CO2 concentrations. Photosynthesis in these plants may be co-limited by Rubisco, GAPDH, and other unknown factor.