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PubMed2026

The evolution of Ca2+-ATPases across plants with profiles in Rhododendron and the function of key members in alleviating high calcium stress.

Ca2+-ATPase (CAP) is a key Ca2+ efflux protein in plants. Our previous research suggests that CAPs may play a crucial role in the adaptation of rhododendrons to high calcium environments. However, the evolution, variation, characteristic expression, and subfunctionalization of this gene family in Rhododendron remain unknown. Through the analysis of pan-genomes and pan-transcriptomes, we elucidated the systematic evolution of CAPs in plants, as well as their characteristic expression patterns in Rhododendron. During the evolutionary process from lower to higher plants, CAPs can be divided into six clades and exhibit structural conservation. CAPs have emerged and differentiated in lower plants such as algae, and they have undergone significant amplification in Eudicots plants like rhododendrons. Three Rhododendron species (Rhododendron bailiense, R. delavayi, and R. irroratum) located in the karst province of Guizhou in Southwest China exhibit the highest copies of CAPs, suggesting a strong association between CAP copy number variation and habitat, particularly in high calcium environments. Through multiple transcriptome analyses, we revealed that CAPs are induced under various environmental/developmental conditions (e.g. karst environments, high altitude, early flower development, hormones, etc.). Co-expression network analysis highlighted key members of calcineurin B-like protein (CBL) and CBL-interacting protein kinases (CIPK) that are associated with the high expression of CAPs. Experimental validation demonstrated that CAPb1 and CAPd1 significantly alleviate high calcium stress, and the CAPb1-CIPK1-CBL1 and CAPd1-CIPK2-CBL1 modules can further enhance the alleviation. These findings provide new insights into the evolution, characteristic expression, and function of CAPs, as well as new perspectives on the high calcium adaptability of rhododendrons.

Journal Article↗
PubMed1989

[HPTLC scanning determination of 6 flavonoids in 166 Rhododendron species].

This paper reports a quantitative determination in the contents of flavonoids in Rhododendron leaves by HPTLC scanning method. The methanol extract of each sample was spotted on a HPTLC silica gel plate (E. Merck F254) alongside with standard substances. Using the upper layer of petroleum ether (60-90 degrees C)-ether-formic acid (62:31:7) as developing solvent I, farrerol, kaempferol and quercetin were well separated. The spots were determined by a single wavelength (366 nm) TLC-scanner, Camag model 76510. The same plate was then further developed by developing solvent II:7 ml of the lower layer of chloroform-methanol-water (7:3:1) plus 0.5 ml of formic acid to separate polystachoside, quercitrin and hyperoside. The densitometric determination of each spot was also carried out with the same scanner. The contents of 6 flavonoids in the leaves of 166 Rhododendron species were thus determined.

Chromatography, Thin Layer↗
PubMed2025

Conservation genomics of a threatened subtropical Rhododendron species highlights the distinct conservation actions required in marginal and admixed populations.

With the impact of climate change and anthropogenic activities, the underlying threats facing populations with different evolutionary histories and distributions, and the associated conservation strategies necessary to ensure their survival, may vary within a species. This is particularly true for marginal populations and/or those showing admixture. Here, we re-sequence genomes of 102 individuals from 21 locations for Rhododendron vialii, a threatened species distributed in the subtropical forests of southwestern China that has suffered from habitat fragmentation due to deforestation. Population structure results revealed that R. vialii can be divided into five genetic lineages using neutral single-nucleotide polymorphisms (SNPs), whereas selected SNPs divide the species into six lineages. This is due to the Guigu (GG) population, which is identified as admixed using neutral SNPs, but is assigned to a distinct genetic cluster using non-neutral loci. R. vialii has experienced multiple genetic bottlenecks, and different demographic histories have been suggested among populations. Ecological niche modeling combined with genomic offset analysis suggests that the marginal population (Northeast, NE) harboring the highest genetic diversity is likely to have the highest risk of maladaptation in the future. The marginal population therefore needs urgent ex situ conservation in areas where the influence of future climate change is predicted to be well buffered. Alternatively, the GG population may have the potential for local adaptation, and will need in situ conservation. The Puer population, which carries the heaviest genetic load, needs genetic rescue. Our findings highlight how population genomics, genomic offset analysis, and ecological niche modeling can be integrated to inform targeted conservation.

Rhododendron↗
PubMed2026

Exogenous ABA enhances cold tolerance of Rhododendron yedoense var. poukhanense under subzero temperature: integrating physiology, transcriptome, and proteome.

Low temperature limits the growth and ornamental value of evergreen shrubs. Rhododendron yedoense var. poukhanense, an important ornamental shrub from Northeast China, frequently suffers freezing damage during winter. While exogenous abscisic acid (ABA) enhances cold tolerance in many plants, its molecular mechanisms at subzero temperatures remain poorly understood in non-model species lacking chromosome-level reference genomes. This study investigated the effects of exogenous ABA on freezing tolerance in R. yedoense var. poukhanense at -4 °C using an integrated physiological, transcriptomic, and proteomic approach. Cutting seedlings were subjected to four treatments: CK (22°C control), A (22°C + ABA), LT (-4°C), and ALT (-4°C + ABA). Photosynthetic pigments, osmotic regulation substances, antioxidant enzyme activities, and malondialdehyde (MDA) content were measured. Transcriptome sequencing and quantitative proteomics were performed, and transcriptome data were validated by quantitative real-time PCR (qRT-PCR) of 15 selected genes. ABA pretreatment reduced visible cold injury severity, partially preserved photosynthetic pigments, decreased MDA content by 28.7%, and promoted recovery of catalase (+43.6%), superoxide dismutase (+31.1%), and peroxidase (+20.0%) activities under freezing stress. Transcriptome analysis revealed 8, 444 differentially expressed genes (DEGs) in LT versus CK and 6, 481 DEGs in ALT versus CK, representing a 23% reduction in transcriptional reprogramming scope attributable to ABA priming. The ALT versus LT comparison identified only 1, 690 additional DEGs, indicating that most cold-responsive genes were pre-activated during the ABA priming phase. Proteome analysis identified 1, 461 differentially expressed proteins (DEPs) in ALT versus CK. Integrated analysis revealed extensive post-transcriptional regulation, with transcript-protein concordance of only 1.0-4.1%, and co-enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in both omics layers. qRT-PCR validation confirmed high reliability of the transcriptome data (R2 = 0.8500). These findings demonstrate that exogenous ABA enhances freezing tolerance through multi-layered molecular regulation encompassing transcriptional buffering, translational reprogramming, and functional reallocation from photosynthesis to stress protection. This study provides the first integrated physiology-transcriptome-proteome framework for ABA-mediated freezing tolerance in an evergreen ornamental shrub and offers theoretical support for ABA-based winter protection strategies.

Rhododendron yedoense var. Poukhanense↗
PubMed1992

Techniques for clearing ovules for studies of megagametophyte and early postfertilization development in Rhododendron.

Using ovule clearing, more than 33,600 ovules of Rhododendron nuttallii T. W. Booth (Ericaceae) were examined for megagametophyte and early postfertilization stages at daily intervals from anthesis until 3 weeks after pollination. Pretreatments with amyloglucosidase to digest integumentary and gametophyte starch and Stockwell's bleach to remove tannins from the integumentary epidermis were necessary. Ovules were cleared by a combination or modifications of Herr's four-and-a-half or Stelly's hemalum-methyl salicylate techniques and were observed using differential interference contrast optics. The method proved suitable for large-scale quantitative studies of ovule development and fertilization. A general protocol is suggested as a starting point for ovule clearing studies.

Fertilization↗
PubMed1990

[Studies on the chemical constituents of Rhododendron molle G. Don].

Two physiologically active diterpenoids were isolated from the flower of Chinese azalea (Ericaceae Rhododendron molle G. Don). One of them is a new compound, named rhodomollein-III; its structure has been established as 1 through IR, MS, 1HNMR, 13C NMR, 1H-1H COSY, 1H-1H NOESY, 13C-1H COSY and long-range 13C-1HCOSY. The other one is the known rhodojaponin-III.

Diterpenes↗
PubMed1991

Site of action of grayanotoxins in mad honey in rats.

Grayanotoxins are known to occur in honey produced from the nectar of Rhododendrons of the family Ericaceae. Grayanotoxins extracted from honey sample obtained from a patient who experienced severe bradycardia and hypotension after ingesting two tablespoonfuls corresponded to Rhododendron ponticum tetrades. Anaesthetized albino rats were injected with honey extract intracerebroventricularly or intraperitoneally. The intracerebroventricular dose was equivalent to 50 mg honey and i.p. doses were equivalent to 50 mg, 1 mg kg-1 and 5 g kg-1 honey. Marked bradycardia and respiratory rate depression were observed in rats injected with extract equivalent to 1 and 5 g kg-1 honey i.p. and in rats injected with 50 mg i.c.v., but not in rats given 50 mg i.p. In bilaterally vagotomized animals, grayanotoxin-contaminated honey extract was not bradycardic. These results suggest that the sites of cardiac and respiratory actions are within the central nervous system, and that the bradycardic effect of grayanotoxin is mediated by vagal stimulation at the periphery.

Animals↗
PubMed1991

Mad honey poisoning in man and rat.

Grayanotoxins are known to occur in the honey produced from the nectar of Rhododendron ponticum growing on the mountains of the eastern Black Sea region of Turkey and also in Japan, Nepal, Brazil, and some parts of North America and Europe. Two cases of honey intoxication are presented here. Both of the patients experienced severe bradycardia and hypotension after ingestion of honey which was brought from Trabzon, Turkey. Microscopical examination showed Rhododendron ponticum pollen tetrades. Anesthetized albino rats were injected intraperitoneally with toxic honey extract doses equivalent to 1 or 5 g honey/kg. Dose-dependent hypotension, bradycardia and respiratory rate depression were observed. When marked bradycardia (approximately 75% of control value) was reached, rats were given atropine sulfate (2 mg/kg, i.p.) or AF-DX 116 (20 mg/kg, i.p.). Atropine sulfate improved both bradycardia and respiratory rate depression. AF-DX 116, which is a selective M2-muscarinic receptor antagonist, restored only heart rate, but not the respiratory rate depression. These results suggest that M2-muscarinic receptors are involved in cardiotoxicity of grayanotoxin.

Aged↗
PubMed1989

Noninfectious diseases, metabolic diseases, toxicities, and neoplastic diseases of South American camelids.

Although the SAC generally are healthy and tolerant of a wide variety of management schemes, a number of noninfectious diseases have been documented to occur, affecting all body systems. Gastrointestinal diseases appear to be the most common afflictions, particularly dental diseases, indigestion, ulceration of the third compartment, and the various causes of colic, such as enteritis, peritonitis, and intestinal accidents. Diseases of the urinary system (urolithiasis, amyloidosis, and glomerulonephritis in particular), the nervous system (especially various compressive lesions of the spinal cord), and the respiratory system (such as obstructive pulmonary diseases) are not uncommon. Diseases of the cardiovascular system (other than congenital defects), hemolymphatic system, and nonsurgical diseases of the musculoskeletal system only rarely are encountered. Heat stress appears to be a very common problem in certain areas, but other metabolic diseases (ketosis, hypocalcemia, and hypothyroidism) are of minor importance. It is assumed that SAC are susceptible to most of the same toxicities that affect domestic livestock species. The best documented examples appear to be the Ericaceae family of plants (laurels, rhododendrons, and so on) and the organophosphate chlorpyrifos. Neoplasia occasionally is seen; examples include lymphosarcoma, gastric squamous cell carcinoma, and adenocarcinoma. As the longevity of these species increases because of their pet status, neoplasia can be expected to become more common. The treatment of most of these conditions is based upon extrapolation from domestic ruminants.

Animals↗
PubMed1992

[Honey-induced poisoning].

Because of the increasing preference for natural products intoxications induced by consumption of honey will reappear, especially with products bought directly from the beekeeper. In the hospital of Trapezunt about 8 cases of intoxications induced by honey were reported per year. The courses observed appear to be identical to those already described by Xenophon 2400 years ago. Symptoms begin acutely but last rarely for more than 24 hours. Fatal cases are extremely rare. Most prominent symptoms are loss of consciousness, weakness, severe salivation, sweating, vomiting and diarrhea. Beside these symptoms circumoral paresthesias and bradyarrhythmia may occur. Intoxication is induced by certain diterpenes, so called gray-anotoxins, that appear in flowers of different species of rhododendron. Next to close surveillance only symptomatic therapy is generally necessary.

Diterpenes↗
PubMed1989

An experimental study of the anti-HSV-II action of 500 herbal drugs.

Experimental assessments were made on the anti-HSV-II action of 500 herbs by determinations of the virus inhibition logarithm (VIL). 13 highly effective herbs (VIL greater than or equal to 4.00) were screened cut, providing a rational basis for clinical therapy. Among these effective herbs, 10 were aqueous extracts of Artemisia anomala, Centella asiatica, Epimedium Sagittatum, Hibiscus mutabilis, Hosta plantaginea, Hypericum japonicum, Inula japonica, Mosla punctata, Rhododendron simsii, and Rhus chinenses, while 3 were alcohol extracts of Epimedium Sagittatum, Hypericum japonicum, and Mosla punctata.

Antiviral Agents↗