Investigating the Phi Use Efficiency of a NADP Utilizing Phosphite Dehydrogenase in Rice

Phosphite, a reduced form of phosphate, has been proposed to be a better source of phosphorus due to its high mobility in soil and can be used as an alternative fertilizer with herbicide for growing crops engineered with bacterial phosphite dehydrogenase protein from Pseudomonas stutzeri. This enzyme uses NAD as a cofactor and its overexpression could deplete the cellular NAD pool, creating pressure on other cellular biochemical reactions. To take advantage of both NAD and NADP, we mutated the native phosphite dehydrogenase gene for relaxed cofactor specificity and overexpressed it in rice plants. The engineered rice plants were found to metabolize phosphite efficiently. However, use of phosphite as a herbicide was not met by mutated phosphite dehydrogenase overexpressing plants as compared to the rice plants overexpressing wild type phosphite dehydrogenase. Therefore, we conclude that mutant phosphite dehydrogenase has potential industrial application for NADPH regeneration and its use for engineering crops for dual fertilization and weed control system is limited.