Molecular characterization of Leucoanthocyanidin reductase and Flavonol synthase gene in Arachis hypogaea

The Antarctic moss 2-oxoglutarate/Fe(II)-dependent dioxygenases (Pn2-ODD2) enhanced the tolerance to drought and oxidative stress

BACKGROUND

Flavonoid biosynthesis pathway is generally thought unique to land plants and has assisted plants to adapt the terrestrial ecosystems. In this pathway, four 2-oxoglutarate/Fe(II)-dependent dioxygenases (2-ODDs), i.e., flavone synthase I (FNSI), flavanone-3-hydroxylase (F3H), flavonol synthase (FLS) and anthocyanin synthase/leucoanthocyanidin dioxygenase (ANS/LDOX), catalyze the hydroxylation and desaturation reactions. In bryophytes, the earliest land plant group, little is known about the biological functions of these enzymes.

RESULTS

Here, we cloned a Pn2-ODD2 gene of flavonoid biosynthesis pathway from Antarctic moss Pohlia nutans, which was induced by exogenous NaCl, PEG and abscisic acid (ABA) treatment. Overexpression of Pn2-ODD2 increased the drought resistance in Physcomitrium patens and Arabidopsis thaliana during gametophyte growth and seed germination, respectively. Overexpressed-Pn2-ODD2 Arabidopsis also exhibited the enhanced tolerance to oxidative stress, with the downregulation of ROS generation gene and increased the total flavonoid content. Also, overexpression of Pn2-ODD2 decreased the ABA sensitivity in transgenic P. patens and Arabidopsis. Meanwhile, overexpression of Pn2-ODD2 resulted in an increase in both anthocyanins and flavonols in Arabidopsis, which was correlated with the up-regulated anthocyanin biosynthesis gene.

CONCLUSIONS

Taken together, Pn2-ODD2 conferred the resistance to drought and oxidative stress by regulating antioxidant defense system in plants.

Multi-omics analysis revealed the mechanism underlying flavonol biosynthesis during petal color formation in Camellia Nitidissima

BACKGROUND

Camellia nitidissima is a rare, prized camellia species with golden-yellow flowers. It has a high ornamental, medicinal, and economic value. Previous studies have shown substantial flavonol accumulation in C. nitidissima petals during flower formation. However, the mechanisms underlying the golden flower formation in C. nitidissima remain largely unknown.

RESULTS

We performed an integrative analysis of the transcriptome, proteome, and metabolome of the petals at five flower developmental stages to construct the regulatory network underlying golden flower formation in C. nitidissima. Metabolome analysis revealed the presence of 323 flavonoids, and two flavonols, quercetin glycosides and kaempferol glycosides, were highly accumulated in the golden petals. Transcriptome and proteome sequencing suggested that the flavonol biosynthesis-related genes and proteins upregulated and the anthocyanin and proanthocyanidin biosynthesis-related genes and proteins downregulated in the golden petal stage. Further investigation revealed the involvement of MYBs and bHLHs in flavonoid biosynthesis. Expression analysis showed that flavonol synthase 2 (CnFLS2) was highly expressed in the petals, and its expression positively correlated with flavonol content at all flower developmental stages. Transient overexpression of CnFLS2 in the petals increased flavonol content. Furthermore, correlation analysis showed that the jasmonate (JA) pathways positively correlated with flavonol biosynthesis, and exogenous methyl jasmonate (MeJA) treatment promoted CnFLS2 expression and flavonol accumulation.

CONCLUSIONS

Our findings showed that the JA-CnFLS2 module regulates flavonol biosynthesis during golden petal formation in C. nitidissima.

Insight into the Molecular Mechanism of Flower Color Regulation in Rhododendron latoucheae Franch: A Multi-Omics Approach

Rhododendron latoucheae Franch. (R. latoucheae) is a valuable woody plant known for its high ornamental value. While purple flowers are a distinct and attractive variant phenotype of R. latoucheae, the underlying mechanism regulating its flower color is still poorly understood. To investigate the molecular regulatory mechanism responsible for the variation in flower color, we selected plants with white-pink and purple petals as the object and conducted analyses of metabolites, key genes, and transcription factors associated with flower color. A combined metabolome-transcriptome analysis was performed, and the expression of key genes was subsequently verified through qRT-PCR experiments. The results of our study demonstrated a significant enrichment of differential metabolites in the flavonoid metabolic pathway. Changes in anthocyanin content followed the same trend as the observed flower color variations, specifically showing significant correlations with the contents of malvidin-3-O-glucoside, dihydromyricetin, gallocatechin, and peonidin-3-O-glucoside. Furthermore, we identified three key structural genes (F3GT1, LAR, ANR) and four transcription factors (bHLH130, bHLH41, bHLH123, MYB4) that are potentially associated with the biosynthesis of flavonoid compounds, thereby influencing the appearance of purple flower color in R. latoucheae.

Phenotypic, Physiological, and Molecular Response of Loropetalum chinense var. rubrum under Different Light Quality Treatments Based on Leaf Color Changes

Light quality is a vital environmental signal used to trigger growth and to develop structural differentiation in plants, and it influences morphological, physiological, and biochemical metabolites. In previous studies, different light qualities were found to regulate the synthesis of anthocyanin. However, the mechanism of the synthesis and accumulation of anthocyanins in leaves in response to light quality remains unclear. In this study, the Loropetalum chinense var. rubrum "Xiangnong Fendai" plant was treated with white light (WL), blue light (BL), ultraviolet-A light (UL), and blue light plus ultraviolet-A light (BL + UL), respectively. Under BL, the leaves were described as increasing in redness from "olive green" to "reddish-brown". The chlorophyll, carotenoid, anthocyanin, and total flavonoid content were significantly higher at 7 d than at 0 d. In addition, BL treatment also significantly increased the accumulation of soluble sugar and soluble protein. In contrast to BL, ultraviolet-A light increased the malondialdehyde (MDA) content and the activities of three antioxidant enzymes in the leaves, including catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), in varying degrees over time. Moreover, we also found that the CRY-like gene, HY5-like gene, BBX-like gene, MYB-like gene, CHS-like gene, DFR-like gene, ANS-like gene, and UFGT-like gene were significantly upregulated. Furthermore, the SOD-like, POD-like, and CAT-like gene expressions related to antioxidase synthesis were found under ultraviolet-A light conditions. In summary, BL is more conducive to reddening the leaves of "Xiangnong Fendai" and will not lead to excessive photooxidation. This provides an effective ecological strategy for light-induced leaf-color changes, thereby promoting the ornamental and economic value of L. chinense var. rubrum.