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.

Explicating genetic diversity based on ITS characterization and determination of antioxidant potential in sea buckthorn (Hippophae spp.).

BACKGROUND: Sea buckthorn (Hippophae) is in the focus of interest mainly for its positive effects on health of both human and animal organisms. Due to the similarities in vegetative morphology, Hippophae species are often misidentified. Therefore, current study was focused on ITS based sequence characterization of sea buckthorn species and comparative biochemical evaluation for its antioxidant properties. METHODS AND RESULTS: DNA was extracted from leaf samples. Primer pairs K-Lab-SeaBukRhm-ITS1F1- K-Lab-SeaBukRhm-ITS1R1 and K-LabSeaBukTib- ITSF1- K-LabSeaBukTib-ITSR1 were used for PCR amplification. The purified PCR products were outsourced for sequencing. Phylogenetic tree was constructed based on neighbor-joining (NJ) method. Moreover, comparison of antioxidant potential of leaves of two sea buckthorn species (Hippophae rhamnoides and Hippophae tibetana) collected from different regions of Ladakh viz., Stakna, Nubra, DRDO Leh and Zanskar was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3- ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), and Total antioxidant capacity (TAC) by phosphomolybdenum assays. The present investigation led to the differentiation of two sea buckthorn species viz., H. rhamnoides and H. tibetana based on Internal Transcribed Spacer (ITS) region. Moreover, significant variation was observed in antioxidant potential of leaf extracts collected from different regions. CONCLUSIONS: Primary ITS sequence analysis was found to be powerful tool for identification and genetic diversity studies in sea buckthorn. Leaves of sea buckthorn have pronounced antioxidant properties and can be used in food, neutraceuticals and pharmaceutical industries etc. The current study will pave the way to discover small bioactive molecules responsible for antioxidant and anticancer properties in sea buckthorn.

Diversity in sea buckthorn (Hippophae rhamnoides L.) accessions with different origins based on morphological characteristics, oil traits, and microsatellite markers.

Sea buckthorn (Hippophae rhamnoides) is an ecologically and economically important species. Here, we assessed the diversity of 78 accessions cultivated in northern China using 8 agronomic characteristics, oil traits (including oil content and fatty acid composition) in seeds and fruit pulp, and SSR markers at 23 loci. The 78 accessions included 52 from ssp. mongolica, 6 from ssp. sinensis, and 20 hybrids. To assess the phenotypic diversity of these accessions, 8 agronomic fruit traits were recorded and analyzed using principal component analysis (PCA). The first two PCs accounted for approximately 78% of the variation among accessions. The oil contents were higher in pulp (3.46-38.56%) than in seeds (3.88-8.82%), especially in ssp. mongolica accessions. The polyunsaturated fatty acid (PUFA) ratio was slightly lower in the seed oil of hybrids (76.06%) than that of in ssp. mongolica (77.66%) and higher than that of in ssp. sinensis (72.22%). The monounsaturated fatty acid (MUFA) ratio in the pulp oil of ssp. sinensis (57.00%) was highest, and that in ssp. mongolica (51.00%) was equal to the ratio in the hybrids (51.20%). Using canonical correspondence analysis (CCA), we examined the correlation between agronomic traits and oil characteristics in pulp and seeds. Oil traits in pulp from different origins were correlated with morphological groupings (r = 0.8725, p = 0.0000). To assess the genotypic diversity, 23 SSR markers (including 17 loci previously reported) were used among the 78 accessions with 59 polymorphic amplified fragments obtained and an average PIC value of 0.2845. All accessions were classified into two groups based on the UPGMA method. The accessions of ssp. sinensis and ssp. mongolica were genetically distant. The hybrid accessions were close to ssp. mongolica accessions. The 8 agronomic traits, oil characteristics in seed and pulp oils, and 23 SSR markers successfully distinguished the 78 accessions. These results will be valuable for cultivar identification and genetic diversity analysis in cultivated sea buckthorn.

RNA-seq data reveals a coordinated regulation mechanism of multigenes involved in the high accumulation of palmitoleic acid and oil in sea buckthorn berry pulp.

BACKGROUND: Sea buckthorn is a woody oil crop in which palmitoleic acid (C16:1n7, an omega-7 fatty acid (FA)) contributes approximately 40% of the total FA content in berry pulp (non-seed tissue). However, the molecular mechanisms contributing to the high accumulation of C16:1n7 in developing sea buckthorn berry pulp (SBP) remain poorly understood. RESULTS: We identified 1737 unigenes associated with lipid metabolism through RNA-sequencing analysis of the four developmental stages of berry pulp in two sea buckthorn lines, 'Za56' and 'TF2-36'; 139 differentially expressed genes were detected between the different berry pulp developmental stages in the two lines. Analyses of the FA composition showed that the C16:1n7 contents were significantly higher in line 'Za56' than in line 'TF2-36' in the mid-late developmental stages of SBP. Additionally, qRT-PCR analyses of 15 genes involved in FA and triacylglycerol (TAG) biosynthesis in both lines revealed that delta9-ACP-desaturase (ACP-Δ9D) competed with 3-ketoacyl-ACP-synthase II (KASII) for the substrate C16:0-ACP and that ACP-Δ9D and delta9-CoA-desaturase (CoA-Δ9D) gene expression positively correlated with C16:1n7 content; KASII and fatty acid elongation 1 (FAE1) gene expression positively correlated with C18:0 content in developing SBP. Specifically, the abundance of ACP-Δ9D and CoA-Δ9D transcripts in line 'Za56', which had a higher C16:1n7 content than line 'TF2-36', suggests that these two genes play an important role in C16:1n7 biosynthesis. Furthermore, the high expressions of the glycerol-3-phosphate dehydrogenase (GPD1) gene and the WRINKLED1 (WRI1) transcription factor contributed to increased biosynthesis of TAG precursor and FAs, respectively, in the early developmental stages of SBP, and the high expression of the diacylglycerol O-acyltransferase 1 (DGAT1) gene increased TAG assembly in the later developmental stages of SBP. Overall, we concluded that increased ACP-Δ9D and CoA-Δ9D levels coupled with decreased KASII and FAE1 activity is a critical event for high C16:1n7 accumulation and that the coordinated high expression of WRI1, GPD1, and DGAT1 genes resulted in high oil accumulation in SBP. CONCLUSION: Our results provide a scientific basis for understanding the mechanism of high C16:1n7 accumulation in berry pulp (non-seed tissue) and are valuable to the genetic breeding programme for achieving a high quality and yield of SBP oil.

Tandem Mass Tag Based Quantitative Proteomics of Developing Sea Buckthorn Berries Reveals Candidate Proteins Related to Lipid Metabolism.

Sea buckthorn ( Hippophae L.) is an economically important shrub or small tree distributed in Eurasia. Most of its well-recognized medicinal and nutraceutical products are derived from its berry oil, which is rich in monounsaturated omega-7 (C16:1) fatty acid and polyunsaturated omega-6 (C18:2) and omega-3 (C18:3) fatty acids. In this study, tandem mass tags (TMT)-based quantitative analysis was used to investigate protein profiles of lipid metabolism in sea buckthorn berries harvested 30, 50, and 70 days after flowering. In total, 8626 proteins were identified, 6170 of which were quantified. Deep analysis results for the proteins identified and related pathways revealed initial fatty acid accumulation during whole-berry development. The abundance of most key enzymes involved in fatty acid and triacylglycerol (TAG) biosynthesis peaked at 50 days after flowering, but TAG synthesis through the PDAT (phospholipid: diacylglycerol acyltransferase) pathway mostly occurred early in berry development. In addition, the patterns of proteins involved in lipid metabolism were confirmed by combined quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and parallel reaction monitoring analyses. Our data on the proteomic spectrum of sea buckthorn berries provide a scientific basic for understanding lipid metabolism and related pathways in the developing berries.

DNA barcoding based identification of Hippophae species and authentication of commercial products by high resolution melting analysis.

Sea buckthorn (Hippophae), an ancient crop with modern virtues, is increasingly consumed in source of foods and nutraceuticals. The growing demand leads to the adulteration of commercial sea buckthorn products, which is a common form of food fraud. Herein, a high resolution melting assay, targeting a DNA barcoding region of the internal transcribed spacer 2 (ITS2) (Bar-HRM) was developed to identify the seven native Chinese Hippophae species, and to authenticate commercial sea buckthorn products. Melting data from the HRM assay demonstrated that all Hippophae species could be clearly distinguished. Then, application to commercial sea buckthorn products indicated the existence of adulterants or contamination, further confirmed using Sanger sequencing results for PCR products from HRM. The Bar-HRM technique proposed in this work could provide a method for regulatory agencies, promoting consumers trust, and raise the quality and safety of sea buckthorn products.

ISSR markers for gender identification and genetic diagnosis of Hippophae rhamnoides ssp. turkestanica growing at high altitudes in Ladakh region (Jammu and Kashmir).

Hippophae rhamnoides L. ssp. turkestanica (Elaeagnaceae) is a predominantly dioecious and wind-pollinated medicinal plant species. The mature fruits of the species possess antioxidative, anti-inflammatory, antimicrobial, anticancerous, and antistimulatory properties that are believed to improve the immune system. The identification of male and female plants in H. rhamnoides ssp. turkestanica is quite difficult until flowering which usually takes 3-4 years or more. A sex-linked marker can be helpful in establishing the orchards through identification of genders at an early stage of development. Therefore, we studied the genetic diversity of populations in Ladakh with the aim to identify a gender-specific marker using ISSR markers. Fifty-eight ISSR primers were used to characterize the genome of H. rhamnoides ssp. turkestanica, of which eight primers generated 12 sex-specific fragments specific to one or more populations. The ISSR primer (P-45) produced a fragment which faithfully segregates all the males from the female plants across all the three valleys surveyed. This male-specific locus was converted into a SCAR. Forward and reverse primers designed from this fragment amplified a 750-bp sequence in males only, thus specifying it as an informative male-specific sex-linked marker. This SCAR marker was further validated for its capability to differentiate gender on an additional collection of plants, representing three geographically isolated valleys (Nubra, Suru, and Indus) from Ladakh region of India. The results confirmed sex-linked specificity of the marker suggesting that this conserved sequence at the Y chromosome is well preserved through the populations in Ladakh region. At present, there are no reliable markers which can differentiate male from female plants across all the three valleys of Ladakh region at an early stage of plant development. It is therefore envisaged that the developed SCAR marker shall provide a reliable molecular tool for early identification of the sex in this commercial crop. The genetic diversity of populations as surveyed by ISSR primers revealed 85.71 % polymorphism at the population level. The dendrogram obtained divided the genotypes into three different clusters, and the distribution of male and female genotypes in all the clusters was random. The Nei's genetic similarity index was in the range of 0.63-0.96.

Characterization and identification of ISSR markers associated with oil content in sea buckthorn berries.

Bioactive oils extracted from sea buckthorn (Hippophae rhamnoides) berries contain highly nutritional and medicinal compounds; however, the oil contents of sea buckthorn berries are very low. Thirteen inter-simple sequence repeat (ISSR) primers were used to identify markers associated with oil content of dry pulp in 51 cultivars and lines, which clustered into three major groups based on 137 polymorphic markers. Dry pulp oil contents in 45 cultivars and lines in Group I ranged from 6.6 to 33.1%; these accessions belonged to H. rhamnoides ssp mongolica and its hybrids with H. rhamnoides ssp sinensis. Three lines (H. rhamnoides ssp mongolica) in Group II had high dry pulp oil contents (33.7 to 37.5%), whereas three lines of hybrids in Group III had low dry pulp oil contents (10.9 to 17.5%). The dry pulp oil content of H. rhamnoides ssp mongolica (27.2 ± 0.9%) was higher than that of hybrids (12.0 ± 1.2%) (P < 0.01). Four ISSR markers (881340, 8251000, 817380, and 8071100) had positive association with high dry pulp oil content (P < 0.01) using stepwise multiple regression analysis. The use of these ISSR markers is a potential strategy to select genotypes with high dry pulp oil content and suitable parental combinations for improvement of sea buckthorn berries.

Proanthocyanidins in Sea Buckthorn (Hippophaë rhamnoides L.) Berries of Different Origins with Special Reference to the Influence of Genetic Background and Growth Location.

Wild sea buckthorn berries from Finland (Hippophaë rhamnoides ssp. rhamnoides) and China (ssp. sinensis) as well as berries of two varieties of ssp. rhamnoides cultivated in Finland and five of ssp. mongolica cultivated in Canada were compared on the basis of the content and composition of proanthocyanidins (PAs). Among all of the samples, only B-type PAs were found. The contents of dimeric, trimeric, tetrameric, and total PAs were in the range of 1.4-8.9, 1.3-9.5, 1.0-7.1, and 390-1940 mg/100 g of dry weight, respectively. The three subspecies were separated by three validated factors (R(2), 0.724; Q(2), 0.677) in the partial least squares discriminant analysis model. Significant differences in total PAs were found between the ssp. rhamnoides and mongolica samples (p < 0.05). In ssp. rhamnoides, samples grown in northern Finland were characterized by a high amount of total PAs, typically 2-3 times higher than that in the level found in southern Finland. In ssp. sinensis, altitude did not have a systematic effect on the PA composition, suggesting the significance of the interaction between genetic background and growth location.

[Genetic and chemical discrimination of traditional Tibetan medicine seabuckthorn based on DNA barcode and ¹H-NMR metabolic method].

To differentiate three medicinal Hippopahe species of seabuckthorn, a combined genetic and chemical identification method was established in this study. ITS2 and psbA-trnH were tested for identification of 3 species of seabuckthorn. Detection of the kimura 2-parameter (K2P) distance, the neighbor-joining (NJ) tree and the barcoding gap were used to assess the identification efficiency. ¹H-NMR based metabolic method was applied to acquire the profile of metabolites. PCA was used to analysis the metabolite data. The results indicated that DNA barcode combined ¹H-NMR based metabolic method is a powerful tool for the identification of 3 medicinal Hippopahe species of seabuckthorn. The finding demonstrated that different genetic variation and chemical constituents existed among 3 medicinal Hippopahe species of seabuckthorn. The combined identification method will improve the reliability of species discrimination and could be applicable to much other ethnic medicine which has various origins in China.

Isolation of good quality RNA from a medicinal plant seabuckthorn, rich in secondary metabolites.

Medicinal plants are being widely investigated owing to their ability to produce molecules of therapeutic significance. Isolation of good quality RNA is a tedious but primary step towards undertaking molecular biology experiments. However, medicinal plants are rich in secondary metabolites and not amenable to standard RNA isolation protocols involving Guanidine isothiocyanate (GITC). So an RNA isolation protocol from difficult samples (richer in secondary metabolites) is of highest desiderata. Here we propose a new protocol suitable for isolating RNA from plant tissues rich in secondary metabolites. To standard CTAB (Cetyl Trimethyl Ammonium Bromide) buffer, addition of 2% PVPP (polyvinyl polypyrrolidone) and 350 mM beta-mercaptoethanol was found useful. Use of glacial acetic acid (1M) along with ethanol for precipitation after phenolization and chloroform extraction enhanced the RNA yield. This is the first report of using glacial acetic acid in a CTAB based protocol for the precipitation of RNA. This protocol has been validated in medicinal plant Hippophae rhamnoides vern. seabuckthorn, where standard RNA isolation methods involving GITC and TRIZol extraction buffers failed. The RNA isolated by this method was of good quality as gauged by spectrophotometric readings and denaturing agarose gel electrophoresis. To the best of our knowledge, this RNA isolation protocol has never been published before. The RNA thus obtained could be suitably used for the downstream molecular procedures like Reverse Transcription Polymerase Chain Reaction (RT-PCR), Real Time-PCR, cDNA library construction, etc.

High-performance liquid chromatographic fingerprint analysis for different origins of sea buckthorn berries.

Using high-performance liquid chromatography (HPLC), a chemical fingerprint method was developed for investigating and demonstrating the variance of flavonoids among different origins of sea buckthorn berries. Thirty-four samples were analyzed including 15 RS (Hippophae rhamnoides ssp. sinensis) samples, 7 RY (H. rhamnoindes ssp. yunnanensis) samples, 5 RW (H. rhamnoides ssp. wolongensis) samples, 4 NS (H. neurocarpa ssp. stellatopilosa) samples and 3 TI (H. tibetana) samples. In the HPLC chromatograms, 12 compounds were identified as flavonoids, including quercetin 3-O-sophoroside-7-rhamnoside, kaempferol 3-O-sophoroside-7-O-rhamnoside, isorhamnetin 3-O-sophoroside-7-O-rhamnoside, isorhamnetin 3-O-glucoside-7-O-rhamnoside, quercetin 3-O-rutinoside, quercetin 3-O-glucoside, isorhamnetin 3-O-rutinoside, isorhamnetin 3-O-glucoside, quercetin, kaempferol 7-O-rhamnoside, kaempferol and isorhamnetin. Both correlation coefficient of similarity in chromatograms and relative peak areas of characteristic compounds were calculated for quantitative expression of the HPLC fingerprints. Our results revealed that the chromatographic fingerprint combining similarity evaluation could efficiently identify and distinguish sea buckthorn berries from different species. However, no obvious difference between RS and RY suggested that the two subspecies might have very close relationship in terms of chemotaxonomy. The established method was considered to be suitable for fingerprint analysis to check the genuine origin and control the quality of sea buckthorn berries and extracts.