Integrated transcriptomic and WGCNA analyses reveal candidate genes regulating mainly flavonoid biosynthesis in Litsea coreana var. sinensis

Litsea coreana Levl. var. sinensis (Allen) Yang et P. H. Huang is a popular ethnic herb and beverage plant known for its high flavonoid content, which has been linked to a variety of pharmacological benefits and crucial health-promoting impacts in humans. The progress in understanding the molecular mechanisms of flavonoid accumulation in this plant has been hindered due to the deficiency of genomic and transcriptomic resources. We utilized a combination of Illumina and Oxford Nanopore Technology (ONT) sequencing to generate a de novo hybrid transcriptome assembly. In total, 126,977 unigenes were characterized, out of which 107,977 were successfully annotated in seven public databases. Within the annotated unigenes, 3,781 were categorized into 58 transcription factor families. Furthermore, we investigated the presence of four valuable flavonoids-quercetin-3-O-β-D-galactoside, quercetin-3-O-β-D-glucoside, kaempferol-3-O-β-D-galactoside, and kaempferol-3-O-β-D-glucoside in 98 samples, using high-performance liquid chromatography. A weighted gene co-expression network analysis identified two co-expression modules, MEpink and MEturquoise, that showed strong positive correlation with flavonoid content. Within these modules, four transcription factor genes (R2R3-MYB, NAC, WD40, and ARF) and four key enzyme-encoding genes (CHI, F3H, PAL, and C4H) emerged as potential hub genes. Among them, the R2R3-MYB (LcsMYB123) as a homologous gene to AtMYB123/TT2, was speculated to play a significant role in flavonol biosynthesis based on phylogenetic analysis. Our findings provided a theoretical foundation for further research into the molecular mechanisms of flavonoid biosynthesis. Additionally, The hybrid transcriptome sequences will serve as a valuable molecular resource for the transcriptional annotation of L. coreana var. sinensis, which will contribute to the improvement of high-flavonoid materials.

Biotechnological Applications and Health-Promoting Properties of Flavonols: An Updated View

Flavonols are a subclass of natural flavonoids characterized by a remarkable number of biotechnological applications and health-promoting properties. They attract researchers' attention due to many epidemiological studies supporting their usage. They are phytochemicals commonly present in our diet, being ubiquitous in the plant kingdom and, in particular, relatively very abundant in fruits and vegetables. All these aspects make flavonols candidates of choice for the valorization of products, based on the presence of a remarkable number of different chemical structures, each one characterized by specific chemical features capable of influencing biological targets inside the living organisms in very different manners. In this review, we analyzed the biochemical and physiological characteristics of flavonols focalizing our attention on the most promising compounds to shed some light on their increasing utilization in biotechnological applications in processing industries, as well as their suitable employment to improve the overall wellness of the humankind.

Morphogenesis and vitality of seedlings of Ginkgo biloba in outdoor conditions

Ginkgo biloba L. is a relic tree that is preserved in natural conditions only in China. In the North-East Ukraine ginkgo is only in the process of introduction, but in certain places ginkgo trees are grown for decorative purposes which show high vitality. Therefore a relevant and promising task is the creation of industrial plantations of ginkgo for collection of its leaves. The objective of the study was morphological peculiarities of ginkgo plants and their vital condition depending on the calendar age of the seedlings at the stage when they were transplanted into the soil. For growing ginkgo, in our studies, a combined two-stage system was approbated, accor­ding to which seedlings were grown in greenhouses during 2–3 years, and then moved into soil outdoors. In our study, as planting material we used seedlings of ginkgo from a plant nursery (greenhouse) of Sumy National Agrarian University planted in 2014 and 2015. Seedlings were planted in the soil in early spring. Seedlings for growth completion were planted in rows with inter-row distance of 0.8 m and distance between the plants measuring 2.5–3.0 m. We studied the condition of the seedlings in two variants: variant 1 – three-year old seedlings obtained in the greenhouse were transplanted in spring 2018; variant 2 – two-year old seedlings obtained in greenhouse were transplanted in spring 2017. Comparative morphometric analysis and evaluation of vitality of these plants was performed in August 2019. Both groups of seedlings were five years old at the time of survey. For evaluation of morphometric structure of the ginkgo seedlings and their vital condition we used randomized selections of specimens in amount of up to 30 from plantations of variants 1 and 2. Analysis of the plants was conducted during the end of the vegetative period of 2019, when active growth of the plants stopped. Four main parameters of the plants were recorded: height, value of annual increment, diameter of the stem near the root neck and the number of leaves. Vital condition of the seedlings was evaluated on the basis of algorithm of vital analysis. Vitality of each seedling was evaluated by the coefficient of Q vitality, value of which was in interval from 0 to 1.0. Depending on the value of Q the seedlings were divided into five classes of vitality: 0–0.2 – cc (specimens of the lowest vitality), 0.2–0.4 – c (low vita­lity), 0.4–0.6 – b (average vitality), 0.6–0.8 – a (high vitality), 0.8–1.0 – aa (specimens with highest vitality). Comparative analysis of morphological peculiarities of the ginkgo seedlings revealed that two-year plants transplanted outdoors from the greenhouse had higher annual increment of the main stem, diameter of stem and number of leaves. Vital condition of such seedlings was the highest and was evaluated using Q index, which ranges between vitality of classes b to aa. This allows recommending a two-stage scheme of growing seedlings of ginkgo in North-East Ukraine. The optimum age for transplanting seedlings from greenhouses to open soil is two years.

Flavonoid Biosynthesis Is Likely More Susceptible to Elevation and Tree Age Than Other Branch Pathways Involved in Phenylpropanoid Biosynthesis in Ginkgo Leaves

Ginkgo leaves are always resources for flavonoids pharmaceutical industry. However, the effect of the elevation and tree age changes on flavonoid biosynthesis have not been detailly explored in Ginkgo leaves. In addition, whether these environmental pressures have similar effects on the biosynthesis of other non-flavonoids polyphenolics in phenylpropanoid biosynthesis is not known at present. In this research, de novo transcriptome sequencing of Ginkgo leaves was performed coupled with ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry analyses to obtain a comprehensive understanding of the influence of elevation and tree age on phenylpropanoid biosynthesis. A total of 557,659,530 clean reads were assembled into 188,155 unigenes, of which 135,102 (71.80%) were successfully annotated in seven public databases. The putative DFRs, LARs, and ANRs were significantly up-regulated with the increase of elevation in young Ginkgo tree leaves. The relative concentration of flavonoid derivatives with high parent ion intensity was likely to imply that the elevation increase promoted the biosynthesis of flavonoids. Complex gene variations involved in flavonoid biosynthesis were observed with the tree age increase. However, flavonoid derivatives analysis predicted that the rise of tree age was more likely to be detrimental to the flavonoids manufacture. Otherwise, multiple genes implicated in the synthesis of hydroxycinnamates, lignin, and lignan exhibited fluctuations with the elevation increase. Significantly up-regulated CADs and down-regulated PRDs potentially led to the accumulation of p-Coumaryl alcohol, one of the lignin monomers, and might inhibit further lignification. Overall, the putative DFRs seemed to show more considerable variability toward these stress, and appeared to be the main regulatory point in the flavonoid biosynthesis. Light enhancement caused by elevation increase may be the main reason for flavonoids accumulation. Flavonoid biosynthesis exhibited a greater degree of perturbation than that of hydroxycinnamates, lignins and lignans, potentially suggesting that flavonoid biosynthesis might be more susceptible than other branch pathways involved in phenylpropanoid biosynthesis. This research effectively expanded the functional genomic library and provide new insights into phenylpropanoid biosynthesis in Ginkgo.