Non-targeted metabolomics analysis of flavonoids in rice grains

【Objective】To explore the changes of flavonoids in rice during grain filling period at the metabolome level, which could provide reference for further research on the molecular mechanisms of rice quality changes. 【Method】High quality rice Jinlongyou 2877 was used as the research material, and ordinary rice Tianyouhuazhan was used as the control（CK）. The physicochemical properties of the grains were determined at grains at 7 d of flowering（early stage of grain filling） and 14 d of flowering（middle stage of grain filling）, and non-targeted metabolomics analysis was conducted to screen out differential metabolites. 【Result】There were differences in the physicochemical properties of rice grains of the 2 varieties. Jinlongyou 2877 rice had low chalkiness, high head rice rate and alkali dissipation value, and its rice quality met the premium grade 2 standard set by the Ministry of Agriculture and Rural Affairs, while CK rice quality did not meet the high quality standard. A total of 1325 metabolites were detected in grains across both rice varieties at 2 developmental periods, classified into 13 categories. In the early stage of grouting, there were a total of 204 differential metabolites between Jinlongyou 2877 and CK, of which 38 metabolites showed up-regulation and 166 metabolites showed down-regulation. During the middle stage of grouting, Jinlongyou 2877 showed a total of 245 differential metabolites compared to CK, of which 136 metabolites showed up-regulation and 109 metabolites showed down-regulation. The differential metabolites mainly included fatty acyl groups, flavonoids and organic oxygen compounds. KEGG metabolic pathway enrichment analysis showed that the biosynthesis pathways of flavonoids and flavonols were enriched in both the early stage and the middle stage of grain filling, indicating that the biosynthesis pathways of flavonoids and flavonols were important for the quality development of rice. Through further extraction and detection of flavonoids, it was found that during the process of rice grain filling, the flavonoids contents of Jinlongyou 2877 did show an increasing trend, while the flavonoids contents of CK did not show obvious changes. 【Conclusion】High quality rice Jinlongyou 2877 exhibits active flavonoids related metabolic pathways during the early and middle stages of grain filling, leading to increasing accumulation of flavonoids. Flavonoids are key metabolites underlying the divergence in eating and cooking quality between high quality rice Jinlongyou 2877 and conventional rice Tianyouhuazhan.