Mutational Analysis of OsPLDα1 Reveals Its Involvement in Phytic Acid Biosynthesis in Rice Grains

Phospholipids and phytic acid are important phosphorus (P)-containing compounds in rice grains. Phytic acid is considered as a major antinutrient, because the negatively charged phytic acid chelates cations, including essential micronutrients, and decreases their bioavailability to human beings and monogastric animals. To gain an insight into the interplay of these two kinds of phosphorus-containing metabolites, we used the CRISPR/Cas9 system to generate mutants of a phospholipase D gene (OsPLDα1) and analyzed the mutational effect on metabolites, including phytic acid in rice grains. Metabolic profiling of two ospldα1 mutants revealed depletion in the phosphatidic acid production and lower accumulation of cytidine diphosphate diacylglycerol and phosphatidylinositol. The mutants also showed significantly reduced phytic acid content as compared to their wild-type parent, and the expression of the key genes involved in the phytic acid biosynthesis was altered in the mutants. These results demonstrate that OsPLDα1 not only plays an important role in phospholipid metabolism but also is involved in phytic acid biosynthesis, most probably through the lipid-dependent pathway, and thus revealed a potential new route to regulate phytic acid biosynthesis in rice.