Improved the Activity of Phosphite Dehydrogenase and its Application in Plant Biotechnology

Phosphorus (P) is a nonrenewable resource, which is one of the major challenges for sustainable agriculture. Although phosphite (Phi) can be absorbed by the plant cells through the Pi transporters, it cannot be metabolized by plant and unable to use as P fertilizers for crops. However, transgenic plants that overexpressed phosphite dehydrogenase (PtxD) from bacteria can utilize phosphite as the sole P source. In this study, we aimed to improve the catalytic efficiency of PtxD from Ralstonia sp.4506 (PtxD_R4506), by directed evolution. Five mutations were generated by saturation mutagenesis at the 139th site of PtxD _R4506 and showed higher catalytic efficiency than native PtxD_R4506. The PtxD_Q showed the highest catalytic efficiency (5.83-fold as compared to PtxD_R4506) contributed by the 41.1% decrease in the K _m and 2.5-fold increase in the k _cat values. Overexpression of PtxD_Q in Arabidopsis and rice showed increased efficiency of phosphite utilization and excellent development when phosphite was used as the primary source of P. High-efficiency PtxD transgenic plant is an essential prerequisite for future agricultural production using phosphite as P fertilizers.