Identification of the key flavonoid and lipid synthesis proteins in the pulp of two sea buckthorn cultivars at different developmental stages

Optimizing the Solvent Selection of the Ultrasound-Assisted Extraction of Sea Buckthorn (Hippophae rhamnoides L.) Pomace: Phenolic Profiles and Antioxidant Activity

Sea buckthorn pomace (SBP) is a by-product of sea buckthorn processing that is rich in bioactive compounds. In this study, different active ingredients were extracted by using different solvents (water, methanol, ethanol, glycerol, ethyl acetate, and petroleum ether) combined with an ultrasonic assisted method. The correlation between the active ingredients and antioxidant properties of the extract was studied, which provided a research basis for the comprehensive utilization of SBP. This study revealed that the 75% ethanol extract had the highest total phenolic content (TPC) of 42.86 ± 0.73 mg GAE/g, while the 75% glycerol extract had the highest total flavonoid content (TFC) of 25.52 ± 1.35 mg RTE/g. The ethanol extract exhibited the strongest antioxidant activity at the same concentration compared with other solvents. The antioxidant activity of the ethanol, methanol, and glycerol extracts increased in a concentration-dependent manner. Thirteen phenolic compounds were detected in the SBP extracts using UPLC-MS/MS analysis. Notably, the 75% glycerol extract contained the highest concentration of all identified phenolic compounds, with rutin (192.21 ± 8.19 μg/g), epigallocatechin (105.49 ± 0.69 μg/g), and protocatechuic acid (27.9 ± 2.38 μg/g) being the most abundant. Flavonols were found to be the main phenolic substances in SBP. A strong correlation was observed between TPC and the antioxidant activities of SBP extracts. In conclusion, the choice of solvent significantly influences the active compounds and antioxidant activities of SBP extracts. SBP extracts are a valuable source of natural phenolics and antioxidants.

The Systematics, Reproductive Biology, Biochemistry, and Breeding of Sea Buckthorn-A Review

Both the fruit flesh and seeds of sea buckthorn have multiple uses for medicinal and culinary purposes, including the valuable market for supplementary health foods. Bioactive compounds, such as essential amino acids, vitamins B, C, and E, carotenoids, polyphenols, ursolic acid, unsaturated fatty acids, and other active substances, are now being analyzed in detail for their medicinal properties. Domestication with commercial orchards and processing plants is undertaken in many countries, but there is a large need for improved plant material with high yield, tolerance to environmental stress, diseases, and pests, suitability for efficient harvesting methods, and high contents of compounds that have medicinal and/or culinary values. Applied breeding is based mainly on directed crosses between different subspecies of Hippophae rhamnoides. DNA markers have been applied to analyses of systematics and population genetics as well as for the discrimination of cultivars, but very few DNA markers have as yet been developed for use in selection and breeding. Several key genes in important metabolic pathways have, however, been identified, and four genomes have recently been sequenced.

Temporospatial pattern of flavonoid metabolites and potential regulatory pathway of PbMYB211-coordinated kaempferol-3-O-rhamnoside biosynthesis in Phoebe bournei

Phoebe is a well-known timber tree species that contains abundant metabolites characterized by flavonoids that are widely used in the pharmaceutical industry. Nevertheless, temporospatial flavonoid metabolism variations substantially impact the Phoebe industry. Thus, a metabolomics analysis was carried out and identified 465 metabolites (102 flavonoids) in P. bournei, revealing distinct distribution patterns among five studied organs, and most of the flavonoids were dominant in the leaves. Furthermore, three kaempferol glycoside derivatives were significantly accumulated in the leaves and showed higher contents in young leaves than in mature leaves and differences between spring and autumn. For instance, greater accumulation of kaempferol-7-O-rhamnoside was detected in spring, whereas higher contents of kaempferol-3-O-arabinofuranoside and kaempferol-3-O-rhamnoside were found in autumn. Integrated metabolomics and transcriptomics identified 20 transcription factors (TFs) and 12 structural genes that participate in kaempferol derivative synthesis and elucidated a potential regulatory mechanism in P. bournei. Of the identified genes, PbMYB211 might contribute significantly to the kaempferol-3-O-rhamnoside content by regulating the target structural gene PbUGT139, as revealed by transient overexpression analysis. Overall, this study illuminated the temporospatial accumulation of flavonoids among different organs, seasons, and developmental stages in P. bournei and elucidated a potential regulatory pathway of kaempferol-3-O-rhamnoside. The results provide important insights into harvest techniques and a theoretical basis for the comprehensive utilization of P. bournei.

Flavonoid synthesis in Lamiophlomis rotata from Qinghai-Tibet Plateau is influenced by soil properties, microbial community, and gene expression

Lamiophlomis rotata is a medicinal plant in Qinghai-Tibet Plateau, in which flavonoid compounds are the major medicinal components. However, it remains unclear how flavonoid metabolism of L. rotata is influenced by soil properties and microbial community. In this study, we collected L. rotata seedlings and rhizosphere soils from five habitats ranging from 3750 to 4270 m of altitude and analyzed the effects of habitat conditions on flavonoid metabolism. The activities of peroxidase, cellulase, and urease were increased with altitude, while those of alkaline phosphatase, alkaline protease, and sucrase were decreased with altitude. Analysis of OTUs showed that the total number of bacterial genera was higher than that of fungal genera. The highest number of fungal genera was 132, and that of bacterial genera was 33 in Batang (BT) town in Yushu County at an altitude of 3880 m, suggesting that the fungal communities may play a critical role in L. rotata rhizosphere soils. Flavonoids in leaves and roots of L. rotata shared a similar pattern, with a trend of increasing levels with altitude. The highest flavonoid content measured, 12.94 mg/g in leaves and 11.43 mg/g in roots, was from Zaduo (ZD) County at an altitude of 4208 m. Soil peroxidases affected quercetin content in leaves of L. rotata, while the fungus Sebacina affected flavonoid content in leaves and roots of L. rotata. The expression of PAL, F3'H, FLS, and FNS genes showed a declining trend in leaves with altitude, while F3H showed an increasing trend in both leaves and roots. Overall, soil physicochemical properties and microbial community affect flavonoid metabolism in L. rotata in Qinghai-Tibet Plateau. The variations in flavonoid content and gene expression as well as their associations with soil factors revealed the complexity of the growth conditions and genetic makeup in L. rotata habitats of Qinghai-Tibet Plateau.

Co-regulatory effects of hormone and mRNA-miRNA module on flower bud formation of Camellia oleifera

Few flower buds in a high-yield year are the main factors restricting the yield of Camellia oleifera in the next year. However, there are no relevant reports on the regulation mechanism of flower bud formation. In this study, hormones, mRNAs, and miRNAs were tested during flower bud formation in MY3 ("Min Yu 3," with stable yield in different years) and QY2 ("Qian Yu 2," with less flower bud formation in a high-yield year) cultivars. The results showed that except for IAA, the hormone contents of GA₃, ABA, tZ, JA, and SA in the buds were higher than those in the fruit, and the contents of all hormones in the buds were higher than those in the adjacent tissues. This excluded the effect of hormones produced from the fruit on flower bud formation. The difference in hormones showed that 21-30 April was the critical period for flower bud formation in C. oleifera; the JA content in MY3 was higher than that in QY2, but a lower concentration of GA₃ contributed to the formation of the C. oleifera flower bud. JA and GA₃ might have different effects on flower bud formation. Comprehensive analysis of the RNA-seq data showed that differentially expressed genes were notably enriched in hormone signal transduction and the circadian system. Flower bud formation in MY3 was induced through the plant hormone receptor TIR1 (transport inhibitor response 1) of the IAA signaling pathway, the miR535-GID1c module of the GA signaling pathway, and the miR395-JAZ module of the JA signaling pathway. In addition, the expression of core clock components GI (GIGANTEA) and CO (CONSTANS) in MY3 increased 2.3-fold and 1.8-fold over that in QY2, respectively, indicating that the circadian system also played a role in promoting flower bud formation in MY3. Finally, the hormone signaling pathway and circadian system transmitted flowering signals to the floral meristem characteristic genes LFY (LEAFY) and AP1 (APETALA 1) via FT (FLOWERING LOCUS T) and SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CO 1) to regulate flower bud formation. These data will provide the basis for understanding the mechanism of flower bud alternate formation and formulating high yield regulation measures for C. oleifera.