OsPLGG1-enhanced Photorespiratory Bypass in Rice

Objective By deleting either OsPLGG1a or OsPLGG1b to optimize the pathway in the pre-engineered GOC rice for enhancing photosynthesis and photorespiration of the plant was postulated.

Method The knockout vectors osplgg1a-Cas9 or osplgg1b-Cas9 were constructed and transformed into the GOC rice to obtain transgenic homozygous lines with OsPLGG1a or OsPLGG1b deleted. Resulting photosynthesis and photorespiration of the rice plant were measured to determine the validity of the proposed hypothesis.

Result  The transgenic homozygous lines were successfully obtained to show a similar phenotype of osplgg1a-GOC and osplgg1a plants with stunted growth. The osplgg1b-GOC plants displayed a net photosynthetic rate increase over that of GOC rice. That indicated the OsPLGG1b mutation to be conducive to the retention of chloroplast glycolate, rise of metabolic flux through GOC bypass, and reduction of plant photorespiration metabolism manifested with enriched CO₂ in the chloroplasts.

Conclusion Compared with the GOC rice, the transgenic osplgg1b-GOC plants had an elevated net photosynthetic rate and stomatal conductance. It suggested that the deletion of OsPLGG1b could be a means to enhance the photorespiration metabolism in a rice plant.