Flavanols in somatic cell division and male meiosis of tea (Camellia sinensis) anthers

Transcriptome and metabolome analysis of the developmental changes in Cynanchum thesioides anther

Cynanchum thesioides, a xerophytic species utilized both as a medicinal herb and a food source, plays a significant role in arid and desert ecosystem management. Its inflorescence is an umbellate cyme, each carrying nearly a thousand flowers; however, its fruiting rate remains remarkably low. The normal development of the anther is a necessary prerequisite for plants to produce seeds. However, our understanding of the anther development process in Cynanchum thesioides remains limited. To better understand the pollen development process in Cynanchum thesioides, the stages of pollen development were determined through paraffin sectioning, and observations were made on the distribution characteristics of polysaccharides and lipid droplets in the pollen development of Cynanchum thesioides using Periodic Acid-Schiff stain (PAS) and 0.5% Sudan Black B tissue staining. Concurrently, the gene expression patterns and metabolite profiles were delineated across various developmental stages of Cynanchum thesioides anthers (T1: microspore stage, T2: tetrad stage, T3: mononuclear stage, and T4: maturation stage). The findings revealed that Cynanchum thesioides pollen is in an aggregate form. Polysaccharides gradually accumulate during maturation and lipid droplets form a surrounding membrane, thereby preventing pollen dispersion. Furthermore, transcriptomic and metabolomic analyses across distinct developmental phases uncovered a plethora of differentially expressed genes and metabolites associated with the flavonoid biosynthesis pathway. Flavonoid levels exhibited dynamic changes concurrent with anther development, aligning with the gene regulatory patterns of the corresponding biosynthetic pathways. The study identified 63 differentially accumulated flavonoid compounds and 21 differentially expressed genes associated with flavonoid biosynthesis. Weighted gene co-expression network analysis revealed six MYB and ten bHLH transcription factors as key candidates involved in flavonoid biosynthesis, with CtbHLH (Cluster-6587.1050) and CtMYB (Cluster-6587.31743) specifically regulating structural genes within the pathway. These findings underscore the pivotal role of flavonoid biosynthesis in anther development of Cynanchum thesioides. In conclusion, this research offers a comprehensive insight into the anther development process in Cynanchum thesioides.

Metabolomic and Confocal Laser Scanning Microscopy (CLSM) Analyses Reveal the Important Function of Flavonoids in Amygdalus pedunculata Pall Leaves With Temporal Changes

Amygdalus pedunculata Pall [Rosaceae, Prunus, Prunus pedunculata (Pall.) Maxim.] belongs to the Rosaceae family and is resistant to cold and drought. Ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry and metabolomics were used to track the changes in bioactive metabolites during several stages of Amygdalus pedunculata Pall growth. A total of 827 different metabolites were detected, including 169 flavonoids, 68 organic acids, 35 terpenoids and 2 tannins. Flavonoid biosynthesis and flavone and flavonol biosynthesis were the main synthetic sources of flavonoids. Quercetin, isoquercitrin, and epicatechin as biomarkers related to growth and development were found. Quercetin connects the biosynthesis of flavonoids and the biosynthesis of flavones and flavonols. The contents of isoquercitrin and epicatechin increased uniformly during the whole growth process from the flowering stage to the fruit ripening stage, indicating that play key roles in the fruit growth and ripening stages of this plant. The tissue location and quantitative analysis of flavonoids in leaves at different stages were performed by confocal laser scanning microscopy. The flavonoids were mainly distributed in the palisade tissue and spongy tissue, indicating the need for protection of these sensitive tissues in particular. Through comprehensive and systematic analysis, the temporal distribution of flavonoids in the process of their leaves growth was determined. These results clarify the important role of flavonoids in the developmental process of Amygdalus pedunculata Pall.

Comparative analysis of the transcriptome, methylome, and metabolome during pollen abortion of a seedless citrus mutant

Pollen abortion could be mainly attributed to abnormal meiosis in the mutant. Multiomics analysis uncovered significant epigenetic variations between the mutant and its wild type during the pollen abortion process. Male sterility caused by aborted pollen can result in seedless fruit. A seedless Ponkan mandarin mutant (bud sport) was used to compare the transcriptome, methylome, and metabolome with its progenitor to understand the mechanism of citrus pollen abortion. Cytological observations showed that the anther of the mutant could form microspore mother cells, although the microspores failed to develop fertile pollen at the anther dehiscence stage. Based on pollen phenotypic analysis, pollen abortion could be mainly attributed to abnormal meiosis in the mutant. A transcriptome analysis uncovered the molecular mechanisms underlying pollen abortion between the mutant and its wild type. A total of 5421 differentially expressed genes were identified, and some of these genes were involved in the meiosis, hormone biosynthesis and signaling, carbohydrate, and flavonoid pathways. A total of 50,845 differentially methylated regions corresponding to 15,426 differentially methylated genes in the genic region were found between the mutant and its wild type by the methylome analysis. The expression level of these genes was negatively correlated with their methylation level, especially in the promoter regions. In addition, 197 differential metabolites were identified between the mutant and its wild type based on the metabolome analysis. The transcription and metabolome analysis further indicated that the expression of genes in the flavonoid, carbohydrate, and hormone metabolic pathways was significantly modulated in the pollen of the mutant. These results indicated that demethylation may alleviate the silencing of carbohydrate genes in the mutant, resulting in excessive starch and sugar hydrolysis and thereby causing pollen abortion in the mutant.

Site-specific accumulation and dynamic change of flavonoids in Apocyni Veneti Folium

Site-specific accumulation of flavonoids in Apocyni Veneti Folium was determined by laser scanning confocal microscope (LSCM) and the localization of catechins also was observed via vanillin-HCl staining under the conventional optical microscope. The contents of five flavonoids in Apocyni Veneti Folium from different harvest times and growth parts were measured using HPLC method. LSCM observation showed that flavonoids are accumulated in cuticle of epidermal cells and vessel walls, especially in protoplasts and nucleolus of the collenchyma cells and the epidermal cells. Catechins are localized in the palisade parenchyma cells and vessel walls, particularly in the laticifers found in the phloem. On the basis of the difference of the maximal emission wavelength between quercetin and kaempferol derivatives which have fluorescence behavior by appropriate treatment, kaempferol and its derivatives are localized exclusively in the cuticle. Results showed that the content of astragalin in Apocyni Veneti Folium from different parts revealed the decreasing trend, while hyperin and isoquercitrin were higher in June and July analyzed by HPLC. In summary, the site-specific accumulation of flavonoids in Apocyni Veneti Folium can be determined by LSCM and vanillin-HCl staining. The contents of flavonoids in Apocyni Veneti Folium are correlated with harvest times and growth parts.

Loss of nuclear flavanols during drought periods in Taxus baccata

Normally, needles of Taxus baccata during the growth period prominently stain blue for nuclear flavanols with the histochemical DMACA procedure. However, under excess heat and drought conditions, nuclear flavanols of current-year needles decline to zero. Nevertheless, greenish-yellow-coloured flavonols (quercetin derivatives) were still observed in nuclei. All of these yellow nuclei were in a silenced state and without mitosis. This link between drought and loss of nuclear flavanols was found in 3 years, 2003, 2007 and 2010. In 2007, exceptional drought occurred in early spring, interrupted by short rains. This, in turn, led to flushing of new sprouts, a characteristic feature in which nuclei were overloaded with flavanols. By the end of three drought periods, all nuclei developed blue-coloured nuclear flavanols. The flavanols seem to be associated with the histone proteins of chromatin. The oxidative degradation of catechin in Tris buffer (pH 8.0) containing MgCl2 was studied in the presence of the H4-core fragment TYTEHAKRKTVTAMD, modified according to the epigenetic histone code. The results show that catechin degradation can be significantly inhibited by the non-modified peptides and the methylated peptides (methylation at both lysine residues). The acetylated and formylated peptides do not show this behaviour. These observations indicate that flavanol association at chromosomes appears to be regulated by the epigenetic histone code.

Significance of flavonoids in plant resistance and enhancement of their biosynthesis

The roles of flavonoids in plant defence against pathogens, herbivores, and environmental stress are reviewed and their significant contribution to plant resistance is discussed. The induction of flavonoids is of particular interest for gathering evidence of their roles. Tools are mentioned which may enhance flavonoid biosynthesis and accumulation. These include metabolic engineering and UV light. The induction of defence-related flavonoids is modified by other determining factors and competition between growth and secondary metabolism may exist. In an evolutionary context, stress-related oxidative pressure may have been a major trigger for the distribution and abundance of flavonoids. UV protection is one of their most significant, or even the most significant, functional role for flavonoids. The multi-functionality of these compounds, however, often complicates the interpretation of experimental results but, overall, it supports the importance of flavonoids.