Combining transcriptome and metabolome analysis to understand the response of sorghum to Melanaphis sacchari.

BACKGROUND: The sorghum aphid Melanaphis sacchari (Zehntner) (Homoptera: Aphididae) is an important insect in the late growth phase of sorghum (Sorghum bicolor L.). However, the mechanisms of sorghum response to aphid infestation are unclear. RESULTS: In this paper, the mechanisms of aphid resistance in different types of sorghum varieties were revealed by studying the epidermal cell structure and performing a transcriptome and metabolome association analysis of aphid-resistant and aphid-susceptible varieties. The epidermal cell results showed that the resistance of sorghum to aphids was positively correlated with epidermal cell regularity and negatively correlated with the intercellular space and leaf thickness. Transcriptome and metabolomic analyses showed that differentially expressed genes in the resistant variety HN16 and susceptible variety BTX623 were mainly enriched in the flavonoid biosynthesis pathway and differentially expressed metabolites were mainly related to isoflavonoid biosynthesis and flavonoid biosynthesis. The q-PCR results of key genes were consistent with the transcriptome expression results. Meanwhile, the metabolome test results showed that after aphidinfestation, naringenin and genistein were significantly upregulated in the aphid-resistant variety HN16 and aphid-susceptible variety BTX623 while luteolin was only significantly upregulated in BTX623. These results show that naringenin, genistein, and luteolin play important roles in plant resistance to aphid infestation. The results of exogenous spraying tests showed that a 1‰ concentration of naringenin and genistein is optimal for improving sorghum resistance to aphid feeding. CONCLUSIONS: In summary, the physical properties of the sorghum leaf structure related to aphid resistance were studied to provide a reference for the breeding of aphid-resistant varieties. The flavonoid biosynthesis pathway plays an important role in the response of sorghum aphids and represents an important basis for the biological control of these pests. The results of the spraying experiment provide insights for developing anti-aphid substances in the future.

[Transcriptional regulation mechanism of differential accumulation of flavonoids in leaves and roots of Sarcandra glabra based on metabonomics and transcriptomics].

This study aims to explore the molecular regulation mechanism of the differential accumulation of flavonoids in the leaves and roots of Sarcandra glabra. Liquid chromatography-mass spectrometry(LC-MS) and high-throughput transcriptome sequencing(RNA-seq) were employed to screen out the flavonoid-related differential metabolites and differentially expressed genes(DEGs) encoding key metabolic enzymes. Eight DEGs were randomly selected for qRT-PCR verification. The results showed that a total of 37 flavonoid-related differential metabolites between the leaves and roots of S. glabra were obtained, including pinocembrin, phlorizin, na-ringenin, kaempferol, leucocyanidin, and 5-O-caffeoylshikimic acid. The transcriptome analysis predicted 36 DEGs associated with flavonoids in the leaves and roots of S. glabra, including 2 genes in the PAL pathway, 3 genes in the 4CL pathway, 2 genes in the CHS pathway, 4 genes in the CHI pathway, 2 genes in the FLS pathway, 1 gene in the DFR pathway, 1 gene in the CYP73A pathway, 1 gene in the CYP75B1 pathway, 3 genes in the PGT1 pathway, 6 genes in the HCT pathway, 2 genes in the C3'H pathway, 1 gene in the CCOAOMT pathway, 1 gene in the ANR pathway, 1 gene in the LAR pathway, 2 genes in the 3AT pathway, 1 gene in the BZ1 pathway, 2 genes in the IFTM7 pathway, and 1 gene in the CYP81E9 pathway. Six transcription factors, including C2H2, bHLH, and bZIP, were involved in regulating the differential accumulation of flavonoids in the leaves and roots of S. glabra. The qRT-PCR results showed that the up-or down-regulated expression of the 8 randomly selected enzyme genes involved in flavonoid synthesis in the leaves and roots of S. glabra was consistent with the transcriptome sequencing results. This study preliminarily analyzed the transcriptional regulation mechanism of differential accumulation of flavonoids in the leaves and roots of S. glabra, laying a foundation for further elucidating the regulatory effects of key enzyme genes and corresponding transcription factors on the accumulation of flavonoids in S. glabra.

Integrated Full-Length Transcriptome and Metabolome Profiling Reveals Flavonoid Regulation in Response to Freezing Stress in Potato.

Cold stress impairs plant growth and development, resulting in crop failure. Cultivated potato (Solanum tuberosum L.) is sensitive to freezing, while its wild relative, S. commersonii, has a strong freezing tolerance. To decipher the anti-freezing mechanism of CM, we carried out a transcriptomic and metabolomic analysis of an anti-freezing variety of CM (a type of S. commersonii) and a freeze-sensitive variety of DM (a type of Solanum tuberosum L.). A total of 49,232 high-quality transcripts from 12,811 gene loci, including 46,772 coding sequences and 2018 non-coding RNAs, were identified. KEEG enrichment analysis of differentially expressed genes (DEGs) between the two varieties showed that the flavonoid biosynthesis pathway was strongly induced by freezing stress, which was proven by flavonoid metabolome analysis. Consistent with the accumulation of more flavonoids, nearly all the pathway genes were significantly upregulated in CM than those in DM. The transcript levels of two chalcone synthase (CHS-1) isoforms and four isoforms of flavonoid 3'-hydroxylase (F3'H-1) were confirmed by qRT-PCR. Co-expression analysis identified one Myb-related and three UGTs (UDP-glycosyltransferase) that were significantly upregulated in CM during freezing stress. Our findings support that the flavonoid pathway was significantly enhanced by freezing stress and the greater accumulation ofglycosylatedflavonoids in resistant types than that of sensitive types, maybe accounting for the increased freezing tolerance of freeze-resistant potato varieties.

Comparative analysis of the difference in flavonoid metabolic pathway during coloring between red-yellow and red sweet cherry (Prunus avium L.).

The color of a fruit is an important contributor to the perception of its nutritional value. It is widely acknowledged that the color of sweet cherry changes obviously during ripening. Variations in anthocyanins and flavonoids account for the heterogeneous color of sweet cherries. In this study, we showed that anthocyanins but not carotenoids determine the color of sweet cherry fruits. The difference between red-yellow and red sweet cherry may be attributed to seven anthocyanins, including Cyanidin-3-O-arabinoside, Cyanidin-3,5-O-diglucoside, Cyanidin 3-xyloside, Peonidin-3-O-glucoside, Peonidin-3-O-rutinoside, Cyanidin-3-O-galactoside, Cyanidin-3-O-glucoside (Kuromanin), Peonidin-3-O-rutinoside-5-O-glucoside, Pelargonidin-3-O-glucoside and Pelargonidin-3-O-rutinoside. The content of 85 flavonols differed between red and red-yellow sweet cherries. The transcriptional analysis identified 15 key structural genes involved in the flavonoid metabolic pathway and four R2R3-MYB transcription factors. The expression level of Pac4CL, PacPAL, PacCHS1, PacCHS2, PacCHI, PacF3H1, PacF3H2, PacF3'H, PacDFR, PacANS1, PacANS2, PacBZ1 and four R2R3-MYB were positively correlated with anthocyanin content (ps < 0.05). PacFLS1, PacFLS2 and PacFLS3 expression was negatively correlated with anthocyanin content but positively correlated with flavonols content (ps < 0.05). Overall, our findings suggests that the heterogeneous expression of structural genes in the flavonoid metabolic pathway accounts for the variation in levels of final metabolites, leading to differences between red 'Red-Light' and red-yellow 'Bright Pearl'.

Transcriptome profiling reveals the roles of pigment formation mechanisms in yellow Paeonia delavayi flowers.

The yellow colour of ornamental varieties of tree peony originated from Paeonia delavayi. However, but P. delavayi and Paeonia suffruticosa belong to different subgroups, so hybridization is difficult and results in a long breeding cycle. However, no comprehensive transcriptomic profiling has focused on the colour formation mechanisms of yellow tree peony petals. Analysing the colour formation mechanism of yellow petals in P. delavayi is very important for directional molecular breeding. In this study, the transcriptional map of yellow pigment development in petals was used to analyse the mechanism of petal colour formation. We analysed the genes related to the metabolism of flavonoids and carotenoids and the transcription factors (TFs) involved in P. delavayi var. lutea (pure yellow individual) yellow pigment development using transcriptome sequence profiling. Transcriptome sequence profiles revealed three and four differentially expressed transcripts (DETs) involved in flavonoid biosynthesis and carotenoid biosynthesis, respectively. An analysis of DETs in the flavonoid pathway showed that chalcone synthase (CHS) and chalcone 2´-glucosyltransferases (THC2'GT) act in synergy to synthesize isosalipurposide (ISP). CHS and flavonol synthase (FLS) synergistically synthesize quercetin and kaempferol. DEG analysis of the carotenoid pathway revealed that phytoene synthase (PSY), carotenoid isomerase (CRTISO) and ß-carotene hydroxylases (CHYB) play a key role in regulating lutein formation, and carotenoid cleavage dioxygenase (CCD) plays an important role in the degradation of carotenoids. These two pathways may be regulated by TF families such as bHLH, ARF, and MYB. The results of the transient overexpression of genes showed that CHS and CHI are regulated by PdMYB2. In this study, the molecular mechanism of ISP synthesis was analysed in depth, and the complete metabolic pathway of carotenoids in Paeonia L. was reported for the first time. By studying the formation mechanism of yellow pigment in P. delavayi petals, a breeding strategy for improving flavonol and carotenoid contents and reducing anthocyanin synthesis by genetic engineering was suggested.

Transcriptional regulation mechanism of differential accumulation of flavonoids in leaves and roots of Sarcandra glabra based on metabonomics and transcriptomics / 中国中药杂志

This study aims to explore the molecular regulation mechanism of the differential accumulation of flavonoids in the leaves and roots of Sarcandra glabra. Liquid chromatography-mass spectrometry(LC-MS) and high-throughput transcriptome sequencing(RNA-seq) were employed to screen out the flavonoid-related differential metabolites and differentially expressed genes(DEGs) encoding key metabolic enzymes. Eight DEGs were randomly selected for qRT-PCR verification. The results showed that a total of 37 flavonoid-related differential metabolites between the leaves and roots of S. glabra were obtained, including pinocembrin, phlorizin, na-ringenin, kaempferol, leucocyanidin, and 5-O-caffeoylshikimic acid. The transcriptome analysis predicted 36 DEGs associated with flavonoids in the leaves and roots of S. glabra, including 2 genes in the PAL pathway, 3 genes in the 4CL pathway, 2 genes in the CHS pathway, 4 genes in the CHI pathway, 2 genes in the FLS pathway, 1 gene in the DFR pathway, 1 gene in the CYP73A pathway, 1 gene in the CYP75B1 pathway, 3 genes in the PGT1 pathway, 6 genes in the HCT pathway, 2 genes in the C3'H pathway, 1 gene in the CCOAOMT pathway, 1 gene in the ANR pathway, 1 gene in the LAR pathway, 2 genes in the 3AT pathway, 1 gene in the BZ1 pathway, 2 genes in the IFTM7 pathway, and 1 gene in the CYP81E9 pathway. Six transcription factors, including C2H2, bHLH, and bZIP, were involved in regulating the differential accumulation of flavonoids in the leaves and roots of S. glabra. The qRT-PCR results showed that the up-or down-regulated expression of the 8 randomly selected enzyme genes involved in flavonoid synthesis in the leaves and roots of S. glabra was consistent with the transcriptome sequencing results. This study preliminarily analyzed the transcriptional regulation mechanism of differential accumulation of flavonoids in the leaves and roots of S. glabra, laying a foundation for further elucidating the regulatory effects of key enzyme genes and corresponding transcription factors on the accumulation of flavonoids in S. glabra.

Genome-wide identification of key enzyme-encoding genes and the catalytic roles of two 2-oxoglutarate-dependent dioxygenase involved in flavonoid biosynthesis in Cannabis sativa L.

BACKGROUND: Flavonoids are necessary for plant growth and resistance to adversity and stress. They are also an essential nutrient for human diet and health. Among the metabolites produced in Cannabis sativa (C. sativa), phytocannabinoids have undergone extensive research on their structures, biosynthesis, and biological activities. Besides the phytocannabinoids, C. sativa is also rich in terpenes, alkaloids, and flavonoids, although little research has been conducted in this area. RESULTS: In this study, we identified 11 classes of key enzyme-encoding genes, including 56 members involved in the flavonoid biosynthesis in C. sativa, from their physical characteristics to their expression patterns. We screened the potentially step-by-step enzymes catalyzing the precursor phenylalanine to the end flavonoids using a conjoin analysis of gene expression with metabolomics from different tissues and chemovars. Flavonol synthase (FLS), belonging to the 2-oxoglutarate-dependent dioxygenase (2-ODD) superfamily, catalyzes the dihydroflavonols to flavonols. In vitro recombinant protein activity analysis revealed that CsFLS2 and CsFLS3 had a dual function in converting naringenin (Nar) to dihydrokaempferol (DHK), as well as dihydroflavonols to flavonols with different substrate preferences. Meanwhile, we found that CsFLS2 produced apigenin (Api) in addition to DHK and kaempferol when Nar was used as the substrate, indicating that CsFLS2 has an evolutionary relationship with Cannabis flavone synthase I. CONCLUSIONS: Our study identified key enzyme-encoding genes involved in the biosynthesis of flavonoids in C. sativa and highlighted the key CsFLS genes that generate flavonols and their diversified functions in C. sativa flavonoid production. This study paves the way for reconstructing the entire pathway for C. sativa's flavonols and cannflavins production in heterologous systems or plant culture, and provides a theoretical foundation for discovering new cannabis-specific flavonoids.

Genome-Wide Investigation of Major Enzyme-Encoding Genes in the Flavonoid Metabolic Pathway in Tartary Buckwheat (Fagopyrum tataricum).

Key enzymes play a vital role in plant growth and development. However, the evolutionary relationships between genes encoding key enzymes in the metabolic pathway of Tartary buckwheat flavonoids are poorly understood. Based on the published Tartary buckwheat genome sequence and related Tartary buckwheat transcriptome data, 48 key enzyme-encoding genes involved in flavonoid metabolism were screened from the Tartary buckwheat genome in this study; the chromosome localization, gene structure and promoter elements of these enzyme-encoding gene were also investigated. Gene structure analysis revealed relatively conserved 5' exon sequences among the 48 genes, indicating that the structural diversity of key enzyme-encoding genes is low in Tartary buckwheat. Through promoter analysis, these key enzyme-encoding genes were found to contain a large number of light-response elements and hormone-response elements. In addition, some genes could bind MYB transcription factors, participating in the regulation of flavonoid biosynthesis. The transcription level of the 48 key enzyme-encoding gene varied greatly among tissues. In this study, we identified 48 key enzyme-encoding genes involved in flavonoid metabolic pathways, and elucidated the structure, evolution and tissue-specific expression patterns of these genes. These results lay a foundation for further understanding the functional characteristics and evolutionary relationships of key enzyme-encoding genes involved in the flavonoid metabolic pathway in Tartary buckwheat.