A widely targeted metabolite modificomics strategy for modified metabolites identification in tomato

The structural and functional diversity of plant metabolites is largely created via chemical modification of a basic backbone.However,metabolite modifications in plants have still not been thoroughly investigated by metabolomics approaches.In this study,a widely targeted metabolite modificomics(WTMM)strategy was developed based on ultra-high performance liquid chromatography-quadrupole-linear ion trap(UHPLC-Q-Trap)and UHPLC-Q-Exactive-Orbitrap(UHPLC-QE-Orbitrap),which greatly improved the detection sensitivity and the efficiency of identification of modified metabolites.A metabolite modificomics study was carried out using tomato as a model,and over 34,000 signals with MS2 information were obtained from approximately 232 neutral loss transitions.Unbiased metabolite profiling was also performed by utilizing high-resolution mass spectrometry data to annotate a total of 2,118 metabolites with 125 modification types;of these,165 modified metabolites were identified in this study.Next,the WTMM database was used to assess diseased tomato tissues and 29 biomarkers were analyzed.In summary,the WTMM strategy is not only capable of large-scale detection and quantitative analysis of plant-modified metabolites in plants,but also can be used for plant biomarker development.

Population analysis reveals the roles of DNA methylation in tomato domestication and metabolic diversity

DNA methylation is an important epigenetic marker,yet its diversity and consequences in tomato breeding at the population level are largely unknown.We performed whole-genome bisulfite sequencing(WGBS),RNA sequencing,and metabolic profiling on a population comprising wild tomatoes,landraces,and cultivars.A total of 8,375 differentially methylated regions(DMRs)were identified,with methylation levels progressively decreasing from domestication to improvement.We found that over 20%of DMRs overlapped with selective sweeps.Moreover,more than 80%of DMRs in tomato were not significantly associated with single-nucleotide polymorphisms(SNPs),and DMRs had strong linkages with adjacent SNPs.We additionally profiled 339 metabolites from 364 diverse accessions and further performed a metabolic association study based on SNPs and DMRs.We detected 971 and 711 large-effect loci via SNP and DMR markers,respectively.Combined with multi-omics,we identified 13 candidate genes and updated the polyphenol biosynthetic pathway.Our results showed that DNA methylation variants could complement SNP profiling of metabolite diversity.Our study thus provides a DNA methylome map across diverse accessions and suggests that DNA methylation variation can be the genetic basis of metabolic diversity in plants.

Integration of rhythmic metabolome and transcriptome provides insights into the transmission of rhythmic fluctuations and temporal diversity of metabolism in rice

Various aspects of the organisms adapt to cyclically changing environmental conditions via transcriptional regulation.However,the role of rhythmicity in altering the global aspects of metabolism is poorly characterized.Here,we subjected four rice(Oryza sativa)varieties to a range of metabolic profiles and RNA-seq to investigate the temporal relationships of rhythm between transcription and metabolism.More than 40%of the rhythmic genes and a quarter of metabolites conservatively oscillated across four rice accessions.Compared with the metabolome,the transcriptome was more strongly regulated by rhythm;however,the rhythm of metabolites had an obvious opposite trend between day and night.Through association analysis,the time delay of rhythmic transmission from the transcript to the metabolite level was~4 h under long-day conditions,although the transmission was nearly synchronous for carbohydrate and nucleotide metabolism.The rhythmic accumulation of metabolites maintained highly coordinated temporal relationships in the metabolic network,whereas the correlation of some rhythmic metabolites,such as branched-chain amino acids(BCAAs),was significantly different intervariety.We further demonstrated that the cumulative diversity of BCAAs was due to the differential expression of branched-chain aminotransferase 2 at dawn.Our research reveals the flexible pattern of rice metabolic rhythm existing with conservation and diversity.