Untargeted lipidomic analysis of milled rice under different alternate wetting and soil drying irrigation regimes

Abstract

Alternate wetting and soil drying irrigation (AWD) technique plays crucial influences on grain quality in rice (Oryza sativa L.). Lipids are the third abundant constitutes besides starch and proteins in rice grains and closely related with grain quality. However, it remains unclear about the changes in lipids profiling under different AWD regimes. This study set up three irrigation regimes including conventional irrigation (CI), alternate wetting and moderate soil drying irrigation (AWMD) and alternate wetting and severe soil drying irrigation (AWSD), and employed the untargeted lipidomics approach to explore lipidome changes in milled rice of Yangdao 6 (YD6), and rice cooking and eating quality was also analyzed. The results showed that 7 lipid classes, 55 lipid subclasses, and a total of 1,086 lipid molecular species were identified. Compared with CI regime, AWMD regime mainly altered these lipid subclasses consisting of TG, Cer, DG, BisMePA, PC, PE, MGDG, and DGDG in milled rice and improved cooking and eating quality of rice, while AWSD regime distinctly changed these lipid subclasses like TG, Cer, DG, PC, PE, Hex1Cer, DGDG, and BisMePA, and degraded cooking and eating quality of rice. Specifically, AWMD regime most significantly altered the expressions of these lipid molecules including DGDG(18:0_18:2), DGDG(16:0_14:0), PC(33:1), Cer(t17:0_26:0), and Cer(t17:0_16:0), while AWSD regime most obviously influenced expressions of TG(6:0_14:0_18:3), PC(41:1), TG(19:1_18:4_18:4), Hex1Cer(d18:2_24:0+O), and Hex1Cer(d18:2_24:1). These 10 altered lipid molecules in milled rice can be preferentially used to focus on their relationships with grain quality in rice.