Plant hormones and phenolic acids response to UV-B stress in Rhododendron chrysanthum pall.

Our study aims to identify the mechanisms involved in regulating the response of Rhodoendron Chrysanthum Pall. (R. chrysanthum) leaves to UV-B exposure; phosphorylated proteomics and metabolomics for phenolic acids and plant hormones were integrated in this study. The results showed that UV-B stress resulted in the accumulation of salicylic acid and the decrease of auxin, jasmonic acid, abscisic acid, cytokinin and gibberellin in R. chrysanthum. The phosphorylated proteins that changed in plant hormone signal transduction pathway and phenolic acid biosynthesis pathway were screened by comprehensive metabonomics and phosphorylated proteomics. In order to construct the regulatory network of R. chrysanthum leaves under UV-B stress, the relationship between plant hormones and phenolic acid compounds was analyzed. It provides a rationale for elucidating the molecular mechanisms of radiation tolerance in plants.

Acetylation proteomics and metabolomics analyses reveal the involvement of starch synthase undergoing acetylation modification during UV-B stress resistance in Rhododendron Chrysanthum Pall.

BACKGROUND: Rhododendron chrysanthum Pall. (R. chrysanthum) is a plant that lives in high mountain with strong UV-B radiation, so R. chrysanthum possess resistance to UV-B radiation. The process of stress resistance in plants is closely related to metabolism. Lysine acetylation is an important post-translational modification, and this modification process is involved in a variety of biological processes, and affected the expression of enzymes in metabolic processes. However, little is known about acetylation proteomics during UV-B stress resistance in R. chrysanthum. RESULTS: In this study, R. chrysanthum OJIP curves indicated that UV-B stress damaged the receptor side of the PSII reaction center, with a decrease in photosynthesis, a decrease in sucrose content and an increase in starch content. A total of 807 differentially expressed proteins, 685 differentially acetylated proteins and 945 acetylation sites were identified by quantitative proteomic and acetylation modification histological analysis. According to COG and subcellular location analyses, DEPs with post-translational modification of proteins and carbohydrate metabolism had important roles in resistance to UV-B stress and DEPs were concentrated in chloroplasts. KEGG analyses showed that DEPs were enriched in starch and sucrose metabolic pathways. Analysis of acetylation modification histology showed that the enzymes in the starch and sucrose metabolic pathways underwent acetylation modification and the modification levels were up-regulated. Further analysis showed that only GBSS and SSGBSS changed to DEPs after undergoing acetylation modification. Metabolomics analyses showed that the metabolite content of starch and sucrose metabolism in R. chrysanthum under UV-B stress. CONCLUSIONS: Decreased photosynthesis in R. chrysanthum under UV-B stress, which in turn affects starch and sucrose metabolism. In starch synthesis, GBSS undergoes acetylation modification and the level is upregulated, promotes starch synthesis, making R. chrysanthum resistant to UV-B stress.

Deciphering mycobiota and its functional dynamics in root hairs of Rhododendron campanulatum D. Don through Next-gen sequencing.

The Himalayas provide unique opportunities for the extension of shrubs beyond the upper limit of the tree. However, little is known about the limitation of the biotic factors belowground of shrub growth at these cruising altitudes. To fill this gap, the present study deals with the documentation of root-associated microbiota with their predicted functional profiles and interactions in the host Rhododendron campanulatum, a krummholz species. While processing 12 root samples of R. campanulatum from the sites using Omics we could identify 134 root-associated fungal species belonging to 104 genera, 74 families, 39 orders, 17 classes, and 5 phyla. The root-associated microbiota members of Ascomycota were unambiguously dominant followed by Basidiomycota. Using FUNGuild, we reported that symbiotroph and pathotroph as abundant trophic modes. Furthermore, FUNGuild revealed the dominant prevalence of the saptroptroph guild followed by plant pathogens and wood saprotrophs. Alpha diversity was significantly different at the sites. The heatmap dendrogram showed the correlation between various soil nutrients and some fungal species. The study paves the way for a more in-depth exploration of unidentified root fungal symbionts, their interactions and their probable functional roles, which may serve as an important factor for the growth and conservation of these high-altitude ericaceous plants.

Molecular Mechanism of Exogenous ABA to Enhance UV-B Resistance in Rhododendron chrysanthum Pall. by Modulating Flavonoid Accumulation.

With the depletion of the ozone layer, the intensity of ultraviolet B (UV-B) radiation reaching the Earth's surface increases, which in turn causes significant stress to plants and affects all aspects of plant growth and development. The aim of this study was to investigate the mechanism of response to UV-B radiation in the endemic species of Rhododendron chrysanthum Pall. (R. chrysanthum) in the Changbai Mountains and to study how exogenous ABA regulates the response of R. chrysanthum to UV-B stress. The results of chlorophyll fluorescence images and OJIP kinetic curves showed that UV-B radiation damaged the PSII photosystem of R. chrysanthum, and exogenous ABA could alleviate this damage to some extent. A total of 2148 metabolites were detected by metabolomics, of which flavonoids accounted for the highest number (487, or 22.67%). KEGG enrichment analysis of flavonoids that showed differential accumulation by UV-B radiation and exogenous ABA revealed that flavonoid biosynthesis and flavone and flavonol biosynthesis were significantly altered. GO analysis showed that most of the DEGs produced after UV-B radiation and exogenous ABA were distributed in the cellular process, cellular anatomical entity, and catalytic activity. Network analysis of key DFs and DEGs associated with flavonoid synthesis identified key flavonoids (isorhamnetin-3-O-gallate and dihydromyricetin) and genes (TRINITY_DN2213_c0_g1_i4-A1) that promote the resistance of R. chrysanthum to UV-B stress. In addition, multiple transcription factor families were found to be involved in the regulation of the flavonoid synthesis pathway under UV-B stress. Overall, R. chrysanthum actively responded to UV-B stress by regulating changes in flavonoids, especially flavones and flavonols, while exogenous ABA further enhanced its resistance to UV-B stress. The experimental results not only provide a new perspective for understanding the molecular mechanism of the response to UV-B stress in the R. chrysanthum, but also provide a valuable theoretical basis for future research and application in improving plant adversity tolerance.

Discovery, biosynthesis, organic synthesis, and bioactivities of meroterpenoids from Rhododendron species.

Meroterpenoids discovered in Rhododendrons species possess unique chemical structures and biological activities and are expected to become new drug targets for Alzheimer's disease, metabolic disorders, and chronic kidney disease, and these compounds have attracted increasing attention in recent years. In this study, Rhododendron meroterpenoids and their structures, classifications, racemate distribution, biosynthetic pathways, chemical synthesis, and bioactivities are reviewed prior to 2023.

How will climate change and forest harvesting influence the habitat quality of two culturally salient species?

Boreal landscapes face increasing disturbances which can affect cultural keystone species, i.e. culturally salient species that shape in a major way the cultural identity of a people. Given their importance, the fate of such species should be assessed to be able to act to ensure their perennity. We assessed how climate change and forest harvesting will affect the habitat quality of Rhododendron groenlandicum and Vaccinium angustifolium, two cultural keystone species for many Indigenous peoples in eastern Canada. We used the forest landscape model LANDIS-II in combination with species distribution models to simulate the habitat quality of these two species on the territories of three Indigenous communities according to different climate change and forest harvesting scenarios. Climate-sensitive parameters included wildfire regimes as well as tree growth. Moderate climate change scenarios were associated with an increased proportion of R. groenlandicum and V. angustifolium in the landscape, the latter species also responding positively to severe climate change scenarios. Harvesting had a minimal effect, but slightly decreased the probability of presence of both species where it occurred. According to the modeling results, neither species is at risk under moderate climate change scenarios. However, under severe climate change, R. groenlandicum could decline as the proportion of deciduous trees would increase in the landscape. Climate change mitigation strategies, such as prescribed fires, may be necessary to limit this increase. This would prevent the decrease of R. groenlandicum, as well as contribute to preserve biodiversity and harvestable volumes.

Chalcone-Synthase-Encoding RdCHS1 Is Involved in Flavonoid Biosynthesis in Rhododendron delavayi.

Flower color is an important ornamental feature that is often modulated by the contents of flavonoids. Chalcone synthase is the first key enzyme in the biosynthesis of flavonoids, but little is known about the role of R. delavayi CHS in flavonoid biosynthesis. In this paper, three CHS genes (RdCHS1-3) were successfully cloned from R. delavayi flowers. According to multiple sequence alignment and a phylogenetic analysis, only RdCHS1 contained all the highly conserved and important residues, which was classified into the cluster of bona fide CHSs. RdCHS1 was then subjected to further functional analysis. Real-time PCR analysis revealed that the transcripts of RdCHS1 were the highest in the leaves and lowest in the roots; this did not match the anthocyanin accumulation patterns during flower development. Biochemical characterization displayed that RdCHS1 could catalyze p-coumaroyl-CoA and malonyl-CoA molecules to produce naringenin chalcone. The physiological function of RdCHS1 was checked in Arabidopsis mutants and tobacco, and the results showed that RdCHS1 transgenes could recover the color phenotypes of the tt4 mutant and caused the tobacco flower color to change from pink to dark pink through modulating the expressions of endogenous structural and regulatory genes in the tobacco. All these results demonstrate that RdCHS1 fulfills the function of a bona fide CHS and contributes to flavonoid biosynthesis in R. delavayi.

Evaluation of Rhododendri Mollis Flos and its representative component as a potential analgesic.

Rhododendri Mollis Flos (R. mole Flos), the dried flowers of Rhododendron mole G. Don, have the ability to relieve pain, dispel wind and dampness, and dissolve blood stasis, but they are highly poisonous. The significance of this study is to explore the analgesic application potential of R. mole Flos and its representative component. According to the selected processing methods recorded in ancient literature, the analgesic activities of wine- and vinegar-processed R. mole Flos, as well as the raw product, were evaluated in a writhing test with acetic acid and a formalin-induced pain test. Subsequently, the HPLC-TOP-MS technique was utilized to investigate the changes in active components before and after processing once the variations in activities were confirmed. Based on the results, rhodojaponin VI (RJ-Vl) was chosen for further study. After processing, especially in vinegar, R. mole Flos did not only maintain the anti-nociception but also showed reduced toxicity, and the chemical composition corresponding to these effects also changed significantly. Further investigation of its representative components revealed that RJ-VI has considerable anti-nociceptive activity, particularly in inflammatory pain (0.3 mg/kg) and peripheral neuropathic pain (0.6 mg/kg). Its toxicity was about three times lower than that of rhodojaponin III, which is another representative component of R. mole Flos. Additionally, RJ-VI mildly inhibits several subtypes of voltage-gated sodium channels (IC50 > 200 µM) that are associated with pain or cardiotoxicity. In conclusion, the chemical substances and biological effects of R. mole Flos changed significantly before and after processing, and the representative component RJ-VI has the potential to be developed into an effective analgesic.

Integrated analysis of transcriptome and small RNAome reveals regulatory network of rapid and long-term response to heat stress in Rhododendron moulmainense.

MAIN CONCLUSION: The post-transcriptional gene regulatory pathway and small RNA pathway play important roles in regulating the rapid and long-term response of Rhododendron moulmainense to high-temperature stress. The Rhododendron plays an important role in maintaining ecological balance. However, it is difficult to domesticate for use in urban ecosystems due to their strict optimum growth temperature condition, and its evolution and adaptation are little known. Here, we combined transcriptome and small RNAome to reveal the rapid response and long-term adaptability regulation strategies in Rhododendron moulmainense under high-temperature stress. The post-transcriptional gene regulatory pathway plays important roles in stress response, in which the protein folding pathway is rapidly induced at 4 h after heat stress, and alternative splicing plays an important role in regulating gene expression at 7 days after heat stress. The chloroplasts oxidative damage is the main factor inhibiting photosynthesis efficiency. Through WGCNA analysis, we identified gene association patterns and potential key regulatory genes responsible for maintaining the ROS steady-state under heat stress. Finally, we found that the sRNA synthesis pathway is induced under heat stress. Combined with small RNAome, we found that more miRNAs are significantly changed under long-term heat stress. Furthermore, MYBs might play a central role in target gene interaction network of differentially expressed miRNAs in R. moulmainense under heat stress. MYBs are closely related to ABA, consistently, ABA synthesis and signaling pathways are significantly inhibited, and the change in stomatal aperture is not obvious under heat stress. Taken together, we gained valuable insights into the transplantation and long-term conservation domestication of Rhododendron, and provide genetic resources for genetic modification and molecular breeding to improve heat resistance in Rhododendron.

Alpine Rhododendron population contractions lead to spatial distribution mismatch with their pollinators under climate change.

The effect of global climate change on plant-pollinator interaction is not limited to changes in phenology and richness within communities but also includes the spatial mismatch caused by the inconsistency of geographical distribution changes. Subsequently, the pollinator interaction network may be remodeled or even disrupted. In this study, we simulated the suitable habitat niche of 15 Rhododendron species and their eight pollinator species as well as their overlapping versus geographical mismatch under the current and three future climate change scenarios in 2090s, using MaxEnt. Results showed that the suitable habitat of all Rhododendron species would decrease in 2090s. In particular, 10, 8, and 13 Rhododendron-pollinator assemblages would have a reduced spatial match region under the climate change scenarios, mainly due to the contraction of the suitable habitat of Rhododendron species. The results provide novel insights into the response of plant-pollinator interactions to global warming, useful to prioritize conservation actions of alpine plant ecosystems.

Spectrophotometric and Chromatographic Assessment of Total Polyphenol and Flavonoid Content in Rhododendron tomentosum Extracts and Their Antioxidant and Antimicrobial Activity.

In the literature, the chemical composition of Rhododendron tomentosum is mainly represented by the study of isoprenoid compounds of essential oil. In contrast, the study of the content of flavonoids will contribute to the expansion of pharmacological action and the use of the medicinal plant for medical purposes. The paper deals with the technology of extracts from Rh. tomentosum shoots using ethanol of various concentrations and purified water as an extractant. Extracts from Rh. tomentosum were obtained by a modified method that combined the effects of ultrasound and temperature to maximize the extraction of biologically active substances from the raw material. Using the method of high-performance thin-layer chromatography in a system with solvents ethyl acetate/formic acid/water (15:1:1), the following substances have been separated and identified in all the extracts obtained: rutin, hyperoside, quercetin, and chlorogenic acid. The total polyphenol content (TPC) and total flavonoid content (TFC) were estimated using spectrophotometric methods involving the Folin-Ciocalteu (F-C) reagent and the complexation reaction with aluminum chloride, respectively. A correlation analysis was conducted between antioxidant activity and the polyphenolic substance content. Following the DPPH assay, regression analysis shows that phenolic compounds contribute to about 80% (r2 = 0.8028, p < 0.05) of radical scavenging properties in the extract of Rh. tomentosum. The extract of Rh. tomentosum obtained by ethanol 30% inhibits the growth of test cultures of microorganisms in 1:1 and 1:2 dilutions of the clinical strains #211 Staphylococcus aureus and #222 Enterococcus spp. and the reference strain Pseudomonas aeruginosa ATCC 10145.

Assessing inter-intraspecific variability of leaf vulnerability to embolism for 10 alpine Rhododendron species growing in Southwestern China.

Alpine Rhododendron species are prominent constituents and renowned ornamental plants in alpine ecosystems. Consequently, evaluating the genetic variation in embolism resistance within the genus Rhododendron and predicting their adaptability to future climate change is important. Nevertheless, the assessment of embolism resistance in Rhododendron species remains limited. This investigation aimed to examine leaf vulnerability to embolism across ten alpine Rhododendron species, which are frequently employed as ornamental species in Rhododendron forests in Southwest China. The study analyzed the correlation between embolism resistance and various morphological traits, while also conducting water control experiments to evaluate the relationship between embolism resistance and drought resistance. The outcomes indicated pronounced variations in leaf vulnerability to embolism among species, as reflected by the water potential at 50% of embolized pixels (P50 ). Furthermore, the leaf P50 exhibited a significant positive correlation with vessel diameter (D) (R2 = 0.44, P = 0.03) and vessel wall span (b) (R2 = 0.64, P = 0.005), while displaying a significant negative correlation with vessel reinforcement ((t/b)2 ) (R2 = 0.67, P = 0.004). These findings underscore the reliability of selecting species based on embolism vulnerability to preserve the diversity of alpine ecosystems and foster resilience to climate change.

Integrated metabolomics and transcriptomics reveal molecular mechanisms of corolla coloration in Rhododendron dauricum L.

Rhododendron dauricum L. is a semi-evergreen shrub of high ornamental and medicinal values in Northeast China. To study the molecular mechanisms of corolla coloration in R. dauricum, integrated metabolomics and transcriptomics were performed in R. dauricum featuring purple flowers and R. dauricum var. album featuring white flowers. Comparative metabolomics revealed 25 differential metabolites in the corolla of the two distinct colors, enriched in flavonoids that are closely related to pigmentation in the flower. Differential analysis of the transcriptomics data revealed enrichment of structural genes for flavonoid biosynthesis (99 up- and 58 down-regulated, respectively, in purple corollas compared to white ones). Significantly, CHS and CHI, key genes in the early stage of anthocyanin synthesis, as well as F3H, F3'H, F3'5'H, DFR, ANS, and UFGT that promote the accumulation of pigments in the late stage of anthocyanin synthesis, were up-regulated in R. dauricum (purple color). In R. dauricum var. album, FLS were key genes determining the accumulation of flavonols. In addition, transcriptome-metabolome correlation analysis identified 16 R2R3 MYB transcription factors (out of 83 MYBs) that are important for corolla coloration. Five negative and four positive MYBs were further identified by integrated transcriptional and metabolic network analysis, revealing a key role of MYBA and MYB12 in regulating anthocyanins and flavonols, respectively. Moreover, we validated the function of RdMYBA by creating stable transgenic plants and found that RdMYBA promotes anthocyanin biosynthesis. In summary, we systematically characterized the transcriptome and metabolome of two R. dauricum cultivars with different flower colors and identified MYBs as key factors in modulating corolla coloration.

Exploitation of green synthesized chromium doped zinc oxide nanorods (NRs) mediated by flower extract of Rhododendron arboreum for highly efficient photocatalytic degradation of cationic dyes Malachite green (MG) and Fuchsin basic (FB).

In this work, green method to synthesize chromium-doped zinc oxide (ZnO) nanorods (NRs) using an aqueous flower extract from Rhododendron arboretum is explored. Herein, chromium-doped ZnO NRs were prepared with different amount of chromium doping, varied as 2-10%. The green synthesized products underwent substantial analysis through X-ray diffraction (XRD), spectroscopic such as ultraviolet spectroscopy(UV-Vis) and scanning electron microscopy (SEM) methods. All samples were found to have hexagonal wurtzite ZnO, with average particle sizes of 52.41, 56.6, 54.44, 53.05, and 56.99 nm, respectively, for 2, 4, 6, 8, and 10% chromium doping in ZnO NRs. The Cr-doped ZnO NRs exhibited remarkable photocatalytic degradation activity of cationic dyes under UV-light, i.e., Malachite Green and Fuchsin Basic with degradation of 99.604 and 99.881%, respectively in 90 min. The reusability tests for these green synthesized Cr-doped ZnO NRs have also been carried out, showed 9-11 cycles with 85% of degradation efficiency. In addition, the Cr-doped ZnO NRs exhibited high selectivity for cationic dyes when experiments against mixture of dyes were performed. Photodegradation kinetics followed the pseudo-first-order model. The flower-extract-stabilized chromium-doped ZnO NRs demonstrated high photocatalytic activity toward malachite green and fuchsin basic dyes, potential material for pollution remediation.

Cr-doped ZnO NRs by green method using flower extract of Rhododendon arboretum were prepared for the first time under ambient reaction conditions.Effect of Dopant i.e. Cr on Photocatalytic activity have been exploited.Selective photocatalytic degradation of cationic dyes i.e. MG, and FB has been achieved in 60­90 minutes.Optimization of reaction condition and various parameters has also been carried out.Recyclability of Cr-doped ZnO NRs was also evaluated and were found to be reusable for 11 cycles for degradation.

Study on the characteristics of genetic diversity of different populations of Guizhou endemic plant Rhododendron pudingense based on microsatellite markers.

BACKGROUND: Rhododendron pudingense, firstly discovered in Puding county of Guizhou province in 2020, have adapted to living in rocky fissure habitat, which has important ornamental and economic values. However, the genetic diversity and population structure of this species have been rarely described, which seriously affects the collection and protection of wild germplasm resources. RESULTS: In the present study, 13 pairs of primers for polymorphic microsatellite were used to investigate the genetic diversity of 65 R. pudingense accessions from six different geographic populations. A total of 254 alleles (Na) were obtained with an average of 19.5 alleles per locus. The average values of polymorphic information content (PIC), observed heterozygosity (Ho), and expected heterozygosity (He) were 0.8826, 0.4501, and 0.8993, respectively, These results indicate that the microsatellite primers adopted demonstrate good polymorphism, and the R. pudingense exhibits a high level of genetic diversity at the species level. The average genetic differentiation coefficient (Fst) was 0.1325, suggested that moderate divergence occurred in R. pudingense populations. The average values of genetic differentiation coefficient and gene flow among populations were 0.1165 and 3.1281, respectively. The analysis of molecular variance (AMOVA) indicated that most of the population differences (88%) were attributed to within-population variation. The PCoA results are consistent with the findings of the UPGMA clustering analysis, supporting the conclusion that the six populations of R. pudingense can be clearly grouped into two separate clusters. Based on Mantel analysis, we speculate that the PD population may have migrated from WM-1 and WM-2. Therefore, it is advised to protect the natural habitat of R. pudingense in situ as much as possible, in order to maximize the preservation of its genetic diversity. CONCLUSIONS: This is the first comprehensive analysis of genetic diversity and population structure of R. pudingense in Guizhou province. The research results revealed the high genetic diversity and moderate population diferentiation in this horticulture plant. This study provide a theoretical basis for the conservation of wild resources of the R. pudingense and lay the foundation for the breeding or cultivation of this new species.

Abscisic Acid Affects Phenolic Acid Content to Increase Tolerance to UV-B Stress in Rhododendron chrysanthum Pall.

The presence of the ozone hole increases the amount of UV radiation reaching a plant's surface, and UV-B radiation is an abiotic stress capable of affecting plant growth. Rhododendron chrysanthum Pall. (R. chrysanthum) grows in alpine regions, where strong UV-B radiation is present, and has been able to adapt to strong UV-B radiation over a long period of evolution. We investigated the response of R. chrysanthum leaves to UV-B radiation using widely targeted metabolomics and transcriptomics. Although phytohormones have been studied for many years in plant growth and development and adaptation to environmental stresses, this paper is innovative in terms of the species studied and the methods used. Using unique species and the latest research methods, this paper was able to add information to this topic for the species R. chrysanthum. We treated R. chrysanthum grown in a simulated alpine environment, with group M receiving no UV-B radiation and groups N and Q (externally applied abscisic acid treatment) receiving UV-B radiation for 2 days (8 h per day). The results of the MN group showed significant changes in phenolic acid accumulation and differential expression of genes related to phenolic acid synthesis in leaves of R. chrysanthum after UV-B radiation. We combined transcriptomics and metabolomics data to map the metabolic regulatory network of phenolic acids under UV-B stress in order to investigate the response of such secondary metabolites to stress. L-phenylalanine, L-tyrosine and phenylpyruvic acid contents in R. chrysanthum were significantly increased after UV-B radiation. Simultaneously, the levels of 3-hydroxyphenylacetic acid, 2-phenylethanol, anthranilate, 2-hydroxycinnamic acid, 3-hydroxycinnamic acid, α-hydroxycinnamic acid and 2-hydroxy-3-phenylpropanoic acid in this pathway were elevated in response to UV-B stress. In contrast, the study in the NQ group found that externally applied abscisic acid (ABA) in R. chrysanthum had greater tolerance to UV-B radiation, and phenolic acid accumulation under the influence of ABA also showed greater differences. The contents of 2-phenylethanol, 1-o-p-coumaroyl-ß-d-glucose, 2-hydroxy-3-phenylpropanoic acid, 3-(4-hydroxyphenyl)-propionic acid and 3-o-feruloylquinic ac-id-o-glucoside were significantly elevated in R. chrysanthum after external application of ABA to protect against UV-B stress. Taken together, these studies of the three groups indicated that ABA can influence phenolic acid production to promote the response of R. chrysanthum to UV-B stress, which provided a theoretical reference for the study of its complex molecular regulatory mechanism.

How generalist insect herbivores respond to alien plants? The case of Aphis fabae-Myzus persicae-Rhododendron ponticum.

BACKGROUND: The enemy release hypothesis (ERH) predicts that alien plant species are unsuitable hosts for native phytophagous insects. However, the biotic resistance hypothesis (BRH) predicts that generalist herbivores may prefer an alien plant over their common host plant. In this study, we have tested these two hypotheses by comparing the potential colonization of the invasive Pontic rhododendron (Rhododendron ponticum L.) versus the common rearing host plants by two generalist aphid species (Aphis fabae and Myzus persicae). We assessed (i) the probing behavior using the electrical penetration graph (EPG) technique and (ii) survival and fecundity in Petri dishes. RESULTS: The results showed the inability of A. fabae and Myzus persicae to immediately colonize R. ponticum. Despite their ability to feed on this invasive plant, the two aphid species hardly survived and poorly reproduced. CONCLUSION: Our results are consistent with the ERH, since R. ponticum appeared as an unsuitable host for native phytophagous insects. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Structurally diverse analgesic diterpenoids from the flowers of Rhododendron molle.

Thirteen diterpenoids (1-13), classified into four structurally diverse carbon skeletons, including 1,5-seco-kalmane (1 and 6), grayanane (2-11), kalmane (12), and rhodomollane (13), were isolated from the flowers extract of Rhododendron molle. Among them, rhodomollinols A - E (1-5) were five new diterpenoids and their structures were elucidated by extensive spectroscopic methods including HRESIMS, UV, IR, 1D and 2D NMR, as well as quantum ECD calculations. Rhodomollinol A (1) is the first representative of a 6-deoxy-1,5-seco-kalmane diterpenoid. The abnormal NMR phenomenon of the presence of only 9 carbon resonances instead of 20 carbons in the 13C NMR spectrum of 1 was observed and elucidated by the quantum NMR calculations. All diterpenoids 1-13 showed significant analgesic activities in an acetic acid-induced writhing model. It's the first time to report the analgesic activity of a rhodomollane-type diterpenoid. At a dose of 1.0 mg/kg, diterpenoids 1-3, 6, 8, 9, and 12 reduced the writhe numbers with inhibition rates over 50%, and 9 exhibited stronger analgesic activity with a writhe inhibition rate of 89.7% than that of the positive control morphine. Importantly, even at the lowest dose of 0.04 mg/kg, rhodomollinols A (1) and B (2), rhodomollein X (7), and 2-O-methylrhodojaponin VI (9) still showed more potent analgesic effects than morphine with the writhe inhibition rates of 51.8%, 48.0%, 61.7%, and 60.0%, respectively. A preliminary structure-activity relationship might provide some clues to design potential analgesics on the basis of structurally diverse Ericaceae diterpenoids.

Transcriptome and photosynthetic analyses provide new insight into the molecular mechanisms underlying heat stress tolerance in Rhododendron × pulchrum Sweet.

Rhododendron species provide excellent ornamental use worldwide, yet heat stress (HS) is one of the major threats to their cultivation. However, the intricate mechanisms underlying the photochemical and transcriptional regulations associated with the heat stress response in Rhododendron remain relatively unexplored. In this study, the analyses of morphological characteristics and chlorophyll fluorescence (ChlF) kinetics showed that HS (40 °C/35 °C) had a notable impact on both the donor's and acceptor's sides of photosystem II (PSII), resulting in reduced PSII activity and electron transfer capacity. The gradual recovery of plants observed following a 5-day period of culture under normal conditions indicates the reversible nature of the HS impact on Rhododendron × pulchrum. Analysis of transcriptome data unveiled noteworthy trends: four genes associated with photosynthesis-antenna protein synthesis (LHCb1, LHCb2 and LHCb3) and the antioxidant system (glutamate-cysteine ligase) experienced significant down-regulation in the leaves of R. × pulchrum during HS. Conversely, aseorbate peroxidase and glutathione S-transferase TAU 8 demonstrated an up-regulated pattern. Furthermore, six down-regulated genes (phos-phoenolpyruvate carboxylase 4, sedoheptulose-bisphosphatase, ribose-5-phosphate isomerase 2, high cyclic electron flow 1, beta glucosidase 32 and starch synthase 2) and two up-regulated genes (beta glucosidase 2 and UDP-glucose pyrophosphorylase 2) implicated in photosynthetic carbon fixation and starch/sucrose metabolism were identified during the recovery process. To augment these insights, a weighted gene co-expression network analysis yielded a co-expression network, pinpointing the hub genes correlated with ChlF dynamics' variation trends. The cumulative results showed that HS inhibited the synthesis of photosynthesis-antenna proteins in R. × pulchrum leaves. This disruption subsequently led to diminished photochemical activities in both PSII and PSI, albeit with PSI exhibiting heightened thermostability. Depending on the regulation of the reactive oxygen species scavenging system and heat dissipation, photoprotection sustained the recoverability of R. × pulchrum to HS.

An updated review of the genus Rhododendron since 2010: Traditional uses, phytochemistry, and pharmacology.

Rhododendron, the largest genus of Ericaceae, consists of approximately 1000 species that are widely distributed in Europe, Asia, and North America but mainly exist in Asia. Rhododendron plants have not only good ornamental and economic value but also significant medicinal potential. In China, many Rhododendron plants are used as traditional Chinese medicine or ethnic medicine for the treatment of respiratory diseases, pain, bleeding and inflammation. Rhododendron is known for its abundant metabolites, especially diterpenoids. In the past 13 years, a total of 610 chemical constituents were reported from Rhododendron plants, including 222 diterpenoids, 122 triterpenoids, 103 meroterpenoids, 71 flavonoids and 92 other constituents (lignans, phenylpropanoids, phenolic acids, monoterpenoids, sesquiterpenoids, coumarins, steroids, fatty acids). Moreover, the bioactivities of various extracts and isolates, both in vitro and in vivo, were also investigated. Our review summarized the research progress of Rhododendron regarding traditional uses, phytochemistry and pharmacology in the past 13 years (2010 to December 2022), which will provide new insight for prompting further research on Rhododendron application and drug development.