Silencing of Sulfoquinovosyl Diacylglycerol Synthase 1 Impairs the Glycolipids Accumulation and Photosynthesis in Phosphate-deprived Rice.

Phosphate (Pi) starved crops utilize the phospholipids as a source for internal Pi supply by replacing the non-phosphorus glycolipids. In rice, sulfoquinovosyl diacylglycerol synthase 1 (OsSQD1) functions as a key enzyme to catalyse SQDG formation. In this study, differential expression of OsSQD1 in response to Pi, nitrogen (N), potassium (K) and iron (Fe)-deficiencies in different durations was measured. A electrophoretic mobility shift assay (EMSA) suggests that OsSQD1 is regulated by OsPHR2, an MYB domain-containing transcription factor. The analyses of different lipid species concentrations in a ossqd1-knockout mutant demonstrated that OsSQD1 silencing increased the phospholipid contents and altered the fatty acid composition under Pi-deficiency. Moreover, OsSQD1 silencing reduces glycolipid accumulation under -Pi condition. It also triggered the saturation of fatty acid in phospholipids and glycolipids treated with different Pi regimes. Relative amounts of transcripts related to phospholipid degradation and glycolipid synthesis was assessed to explore the mechanism by which OsSQD1 exerts an effect on lipid homeostasis under -P conditions. Furthermore, OsSQD1 silencing inhibited photosynthesis, especially under Pi-deficient conditions, by down-regulating glycolipids in rice shoots. The study reveals that OsSQD1 plays a key role in lipid homeostasis, especially the glycolipids accumulation under Pi-deficiency, which results in the inhibition of photosynthesis responding to Pi-deficiency. © Crown copyright. Published by Oxford University Press on behalf of the Society for Experimental Biology.