Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the two predominant galactolipids present in the photosynthetic membrane in many photosynthetic organisms, including algae and higher plants. These galactolipids are the main constituents of thylakoid membrane and are essential for chloroplast biogenesis and photoautotrophic growth. In silico analysis revealed that rice ( Oryza sativa L.) genome has three genes encoding MGDG synthase ( OsMGD1, 2 , and 3 ). Although subcellular localization analysis demonstrated that OsMGD2 is localized to chloroplast, its expression was observed mainly in anther and endosperm, suggesting that MGDG might have an important role in the development of flower and grain in rice. Knock-out mutants of OsMGD2 were generated employing the CRISPR/Cas9 system and their morphology, yield and grain quality related traits were studied. The leaf of osmgd2 mutants showed reduced MGDG (∼11.6%) and DGDG (∼9.5%) content with chlorophyll a content decreased by ∼23%, consequently affecting the photosynthesis. The mutants also exhibited poor agronomic performance with plant height and panicle length decreased by ∼12.2 and ∼7.3%, respectively. Similarly, the number of filled grains per panicle was reduced by 43.8%, while the 1000 grain weight was increased by ∼6.3% in the mutants. The milled rice of mutants also had altered pasting properties and decreased linoleic acid content (∼26.6%). Put together, the present study demonstrated that OsMGD2 is the predominantly expressed gene encoding MGDG synthase in anther and grain and plays important roles in plant growth and development, as well as in grain quality.

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.