Integrated Transcriptomics And Metabolomics Analyses Reveal The Nutritional Quality And Molecular Basis Of Different Varieties Of Rice

Rice(Oryza sativa L.)is the main economic crop in the world.Therefore,analyzing the genetic basis of its nutritional quality is an important prerequisite for cultivating new varieties of nutritional health.Cultivar and landrace rice,with unique phenotypic traits and genetic diversity,are important resources for the genetic improvement of rice nutritional quality.The seeds of landrace varieties are usually white,black,red and purple,while the seeds of cultivar are mainly white.To systematically compare the differences in nutritional quality between cultivated rice and landraces,and to mine the key genes that determine the specific nutritional traits of landraces,a total of 114 rice materials were collected in this study,including 35 landraces and 79 cultivar rice.6 landraces and 4 cultivated rice were selected for comparative analysis of metabolism and transcriptome.The differences in metabolism,transcriptome and molecular mechanism between landrace and cultivated varieties of rice were systematically studied.The main results of this study are as follows.1.A rice seed metabolic database was established based on liquid chromatographymass spectrometry,which contained 985 high-quality metabolic signals.A total of 549 key nutritional metabolites were identified and annotated,including amino acids,flavonoids,lipids and vitamins.In addition,principal component analysis and phylogenetic analysis of the metabolic groups of dry rice seeds revealed that there were differences in the accumulation of metabolites between landrace and cultivated rice seeds.The main metabolites of dry seeds of different rice varieties were identified as flavonoids and lipids by thermal graph clustering.2.Principal component analysis(PCA)was performed on the seed metabolites of different rice varieties at 3 germination stages(0h,24 h,48h).There were differences in the accumulation of metabolites between landraces and cultivated varieties at different germination stages.A total of 174 differential accumulation metabolites related to nutritional quality were screened,among which the differential metabolites were mainly lipids,flavonoids and anthocyanin.3.Transcriptome analysis was performed on different varieties of rice seeds,and 1982 differential genes were found through KEGG and GO enrichment analysis,which were mainly enriched in flavonoids and anthocyanin synthesis pathways.4.The weighted co-expression analysis(WGCNA)was used to establish the metabolite-gene correlation network.The differential metabolites were mainly correlated with the genes in flavonoid and anthocyanin synthesis pathways.20 candidate genes that might be involved in anthocyanin structural modification were screened out,and 5glycosylation enzymes were proved to be capable of glycosylation of rice anthocyanin through in vitro enzyme activity experiments.5.Finally,the synthesis pathway of anthocyanin biosynthetic pathway in rice seeds was constructed using transcriptome and metabolomics data.The expression levels of anthocyanin biosynthetic pathway structural genes Os CHS,Os F3’H,Os F3’5’H and Os3 GT in different varieties were verified by q RT-PCR experiments.In this study,multi-omics analysis methods,including transcriptome and metabolomics analysis,combined with in vitro enzyme activity and q RT-PCR experiments were used to systematically compare the differences in anthocyanin biosynthesis pathway and anthocyanin structural diversity between landrace and cultivated rice,which provided new insights for the analysis and utilization of nutritional quality of landrace rice.