Development of fruit color in Rubus chingii Hu (Chinese raspberry): A story about novel offshoots of anthocyanin and carotenoid biosynthesis

Ultrasound-based strategies for the recovery of microalgal carotenoids: Insights from green extraction methods to UV/MS-based identification

Carotenoids, versatile natural pigments with numerous health benefits, face environmental concerns associated with conventional petrochemical-based extraction methods and limitations of their synthetic equivalents. In this context, this study aims to introduce eco-friendly approaches using ultrasound-based strategies (probe and bath) for the extraction of carotenoids from microalgae, initially focusing on Microchloropsis gaditana and subsequently evaluating the versatility of the method by applying it to other microalgae species of interest (Tisochrysis lutea, Porphyridium cruentum, and Phaeodactylum tricornutum) and defatted microalgal residues. Among the approaches evaluated, the 5-min ultrasonic probe system with ethanol showed comparable carotenoid recovery efficiency to the reference method (agitation, 24 h, acetone) (9.4 ± 2.5 and 9.6 ± 3.2 mg g-1 carotenoids per dry biomass, for the green and the reference method, respectively). Moreover, the method's sustainability was demonstrated using the AGREEprep™ software (scored 0.62 out of 1), compared to the traditional method (0.22 out of 1). The developed method yielded high carotenoid contents across species with diverse cell wall compositions (3.1 ± 0.2, 2.1 ± 0.3, and 4.1 ± 0.1 mg g-1 carotenoid per dry biomass for T. lutea, P. cruentum, and P. tricornutum, respectively). Moreover, the application of the method to defatted biomass showed potential for microalgal valorization with carotenoid recovery rates of 41 %, 60 %, 61 %, and 100 % for M.gaditana, P. tricornutum, T. lutea, and P. cruentum, compared to the original biomass, respectively. Furthermore, by using high-performance liquid chromatography with a diode array detector (HPLC-DAD) and high-resolution mass spectrometry (HRMS), we reported the carotenoid and chlorophyll profiles of the different microalgae and evaluated the impact of the eco-friendly methods. The carotenoid and chlorophyll profiles varied depending on the species, biomass, and method used. In summary, this study advances a green extraction method with improved environmental sustainability and shorter extraction time, underscoring the potential of this approach as a valuable alternative for the extraction of microalgal pigments.

Chromosome-scale genome, together with transcriptome and metabolome, provides insights into the evolution and anthocyanin biosynthesis of Rubus rosaefolius Sm. (Rosaceae)

Rubus rosaefolius is a kind of red raspberry possessing high nutritional and pharmaceutical value. Here we present a chromosome-level draft genome of R. rosaefolius. Of the total 131 assembled scaffolds, 70 with a total size of 219.02 Mb, accounting for 99.33% of the estimated genome size, were anchored to seven pseudochromosomes. We traced a whole-genome duplication (WGD) event shared among members of the Rosaceae family, from which were derived 5090 currently detectable duplicated gene pairs (dgps). Of the WGD-dgps 75.09% underwent purifying selection, and approximately three-quarters of informative WGD-dgps expressed their two paralogs with significant differences. We detected a wide variety of anthocyanins in the berries of R. rosaefolius, and their total concentration remained relatively stable during berry development but increased rapidly during the ripening stage, mainly because of the contributions of pelargonidin-3-O-glucoside and pelargonidin-3-O-(6″-O-malonyl)glucoside. We identified many structural genes that encode enzymes, such as RrDFR, RrF3H, RrANS, and RrBZ1, and play key roles in anthocyanin biosynthesis. The expression of some of these genes significantly increased or decreased with the accumulation of pelargonidin-3-O-glucoside and pelargonidin-3-O-(6″-O-malonyl)glucoside. We also identified some transcription factors and specific methylase-encoding genes that may play a role in regulating anthocyanin biosynthesis by targeting structural genes. In conclusion, our findings provide deeper insights into the genomic evolution and molecular mechanisms underlying anthocyanin biosynthesis in berries of R. rosaefolius. This knowledge may significantly contribute to the targeted domestication and breeding of Rubus species.

Correlation between Antimicrobial Activity Values and Total Phenolic Content/Antioxidant Activity in Rubus idaeus L

Plant by-products, which are discarded into the environment, are rich in valuable compounds. The aim of this research was to determine the antibacterial activity of Rubus idaeus L. morphological parts and its correlation with total phenolic content and antioxidant activity. The authors also aimed to evaluate the plant's potential as added-value products. New aspects were revealed for further use and for making novel and natural products. The study's results indicated that raspberry leaves, inflorescences, and fruits could effectively combat three Gram-positive bacteria. According to the findings, among the various plant parts, root and seed extracts had the lowest antibacterial activity. Data revealed moderate, weak, or very weak correlation between the antimicrobial activity and phenolic content parameters. These findings underscore the viability of substituting synthetic antimicrobials with natural alternatives. The present study is significant for preparing novel products as antibacterials by appropriate and optimized processing using all raspberry morphological parts, and the research results show promising prospects for future purposeful utilisation of nature-based products. Raspberry plant parts can find applications in emerging fields that generate economic and environmental value.

Genome-Wide Identification of Expansins in Rubus chingii and Profiling Analysis during Fruit Ripening and Softening

Improving fruit size or weight, firmness, and shelf life is a major target for horticultural crop breeding. It is associated with the depolymerization and rearrangement of cell components, including pectin, hemicellulose, cellulose, and other structural (glyco)proteins. Expansins are structural proteins to loosen plant cell wall polysaccharides in a pH-dependent manner and play pivotal roles in the process of fruit development, ripening, and softening. Rubus chingii Hu, a unique Chinese red raspberry, is a prestigious pharmaceutical and nutraceutical dual-function food with great economic value. Thirty-three RchEXPs were predicted by genome-wide identification in this study, containing twenty-seven α-expansins (EXPAs), three β-expansins (EXPBs), one expansin-like A (EXPLA), and two expansin-like B (EXPLBs). Subsequently, molecular characteristics, gene structure and motif compositions, phylogenetic relationships, chromosomal location, collinearity, and regulatory elements were further profiled. Furthermore, transcriptome sequencing (RNA-seq) and real-time quantitative PCR assays of fruits from different developmental stages and lineages showed that the group of RchEXPA5, RchEXPA7, and RchEXPA15 were synergistically involved in fruit expanding and ripening, while another group of RchEXPA6 and RchEXPA26 might be essential for fruit ripening and softening. They were regulated by both abscisic acid and ethylene and were collinear with phylogenetic relationships in the same group. Our new findings laid the molecular foundation for improving the fruit texture and shelf life of R. chingii medicinal and edible fruit.

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.

Development of Smart Films of a Chitosan Base and Robusta Coffee Peel Extract for Monitoring the Fermentation Process of Pickles

Smart film is widely used in the field of food packaging. The smart film was prepared by adding anthocyanin-rich Robusta coffee peel (RCP) extract into a chitosan (CS)-glycerol (GL) matrix by a solution-casting method. By changing the content of RCP (0, 10%, 15% and 20%) in the CS-GL film, the related performance indicators of CS-GL-RCP films were studied. The results showed that the CS-GL-RCP films had excellent mechanical properties, and CS-GL-RCP15 film maintained the tensile strength (TS) of 16.69 MPa and an elongation-at-break (EAB) of 18.68% with RCP extract. CS-GL-RCP films had the best UV-vis light barrier property at 200-350 nm and the UV transmittance was close to 0. The microstructure observation results showed that CS-GL-RCP films had a dense and uniform cross section, which proved that the RCP extract had good compatibility with the polymer. In addition, the CS-GL-RCP15 film was pH-sensitive and could exhibit different color changes with different pH solutions. So, the CS-GL-RCP15 film was used to detect the fermentation process of pickles at 20 ± 1 °C for 15 days. The pickles were stored in a round pickle container after the boiling water had cooled. The color of the CS-GL-RCP15 film changed significantly, which was consistent with the change of pickles from fresh to mature. The color of the smart film changed significantly with the maturity of pickles, and the difference of ΔE of film increased to 8.89 (15 Days), which can be seen by the naked eye. Therefore, CS-GL-RCP films prepared in this study provided a new strategy for the development of smart packaging materials.

Integrated Physiological and Metabolomic Analyses Reveal the Differences in the Fruit Quality of the Blueberry Cultivated in Three Soilless Substrates

With improving living standards, traditional blueberry planting modes cannot meet commercial demands, and blueberry cultivation with soilless substrate has become a popular solution in the blueberry industry. In this study, different soilless substrate treatments were found to markedly influence fruit appearance and intrinsic quality. The fruit in the 50:50 peat/pine bark (v/v) (FPB) treatment group had the maximum single fruit weight, largest vertical diameter, and brightest color, as well as the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) value, solid-acid ratio and anthocyanin content. The fruit in the 50:50 pine bark/rice husk (v/v) (FBR) treatment group had the highest total phenol and flavonoid levels, largest drip loss value, and lowest total pectin content and firmness value. Metabolomic analysis showed that flavonoid, carbohydrate, and carbohydrate conjugate, and amino acid, peptide, and analog levels were significantly different between groups. Fruit in the FPB group had the highest sucrose, D-fructose 1,6-bisphosphate, salidroside, tectorigenin, naringenin chalcone, trifolirhizin, and galangin contents. The increase in the relative expression of phenylalanine (Phe) promoted the synthesis of fruit polyphenols in the FBR group. Our results provide new insights into the effects of different substrates on the quality of blueberries and a reference for the soilless substrate cultivation of blueberries.

Evaluation of Physiological Coping Strategies and Quality Substances in Purple SweetPotato under Different Salinity Levels

Although salinity stress is one of the principal abiotic stresses affecting crop yield, a suitable concentration of NaCl has proven to be useful for increasing crop quality. This study used low salinity (34 mmol/L NaCl) and high salinity (85 mmol/L) to cultivate purple sweetpotato. Using transcriptomics and metabolomics to profile the pathway indicated that glycometabolism, secondary metabolite biosynthesis and the starch catabolic process were the significant pathways under the salinity stress. Further research showed that purple sweetpotato could regulate genes related to the regulation of the cellular Na+, K+, and other ions concentration in response to the low salinity tolerance, but loses this ability under high salinity. Meanwhile, under low salinity, the activity of antioxidant enzymes and their related gene expression are maintained at a high level. The low salinity influences the monosaccharide composition as well as the content and regulation of genes related to starch synthesis. Quality analysis showed that the low salinity could increase the starch content and influence the amylopectin biosynthesis. It suggested that low salinity promotes substance accumulation. High salinity could increase the anthocyanins biosynthesis and low salinity had a significant impact on phenolic acid and flavonol. Finally, the gene expression levels also prove the low salinity could change the composition and content level of the purple sweetpotato. This study showed that an appropriate concentration of NaCl can be used as an elicitor for application in purple sweetpotato planting.

Comparative metabolomics provides novel insights into the basis of petiole color differences in celery (Apiumgraveolens L.)

Plant metabolites are important for plant development and human health. Plants of celery (Apiumgraveolens L.) with different-colored petioles have been formed in the course of long-term evolution. However, the composition, content distribution, and mechanisms of accumulation of metabolites in different-colored petioles remain elusive. Using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), 1159 metabolites, including 100 lipids, 72 organic acids and derivatives, 83 phenylpropanoids and polyketides, and several alkaloids and terpenoids, were quantified in four celery cultivars, each with a different petiole color. There were significant differences in the types and contents of metabolites in celery with different-colored petioles, with the most striking difference between green celery and purple celery, followed by white celery and green celery. Annotated analysis of metabolic pathways showed that the metabolites of the different-colored petioles were significantly enriched in biosynthetic pathways such as anthocyanin, flavonoid, and chlorophyll pathways, suggesting that these metabolic pathways may play a key role in determining petiole color in celery. The content of chlorophyll in green celery was significantly higher than that in other celery cultivars, yellow celery was rich in carotenoids, and the content of anthocyanin in purple celery was significantly higher than that in the other celery cultivars. The color of the celery petioles was significantly correlated with the content of related metabolites. Among the four celery cultivars, the metabolites of the anthocyanin biosynthesis pathway were enriched in purple celery. The results of quantitative real-time polymerase chain reaction (qRT-PCR) suggested that the differential expression of the chalcone synthase (CHS) gene in the anthocyanin biosynthesis pathway might affect the biosynthesis of anthocyanin in celery. In addition, HPLC analysis revealed that cyanidin is the main pigment in purple celery. This study explored the differences in the types and contents of metabolites in celery cultivars with different-colored petioles and identified key substances for color formation. The results provide a theoretical basis and technical support for genetic improvement of celery petiole color.