A rare non-canonical splice site in Trema orientalis SYMRK does not affect its dual symbiotic functioning in endomycorrhiza and rhizobium nodulation.

BACKGROUND: Nitrogen-fixing nodules occur in ten related taxonomic lineages interspersed with lineages of non-nodulating plant species. Nodules result from an endosymbiosis between plants and diazotrophic bacteria; rhizobia in the case of legumes and Parasponia and Frankia in the case of actinorhizal species. Nodulating plants share a conserved set of symbiosis genes, whereas related non-nodulating sister species show pseudogenization of several key nodulation-specific genes. Signalling and cellular mechanisms critical for nodulation have been co-opted from the more ancient plant-fungal arbuscular endomycorrhizal symbiosis. Studies in legumes and actinorhizal plants uncovered a key component in symbiotic signalling, the LRR-type SYMBIOSIS RECEPTOR KINASE (SYMRK). SYMRK is essential for nodulation and arbuscular endomycorrhizal symbiosis. To our surprise, however, despite its arbuscular endomycorrhizal symbiosis capacities, we observed a seemingly critical mutation in a donor splice site in the SYMRK gene of Trema orientalis, the non-nodulating sister species of Parasponia. This led us to investigate the symbiotic functioning of SYMRK in the Trema-Parasponia lineage and to address the question of to what extent a single nucleotide polymorphism in a donor splice site affects the symbiotic functioning of SYMRK. RESULTS: We show that SYMRK is essential for nodulation and endomycorrhization in Parasponia andersonii. Subsequently, it is revealed that the 5'-intron donor splice site of SYMRK intron 12 is variable and, in most dicotyledon species, doesn't contain the canonical dinucleotide 'GT' signature but the much less common motif 'GC'. Strikingly, in T. orientalis, this motif is converted into a rare non-canonical 5'-intron donor splice site 'GA'. This SYMRK allele, however, is fully functional and spreads in the T. orientalis population of Malaysian Borneo. A further investigation into the occurrence of the non-canonical GA-AG splice sites confirmed that these are extremely rare. CONCLUSION: SYMRK functioning is highly conserved in legumes, actinorhizal plants, and Parasponia. The gene possesses a non-common 5'-intron GC donor splice site in intron 12, which is converted into a GA in T. orientalis accessions of Malaysian Borneo. The discovery of this functional GA-AG splice site in SYMRK highlights a gap in our understanding of splice donor sites.

In vitro antiplasmodial activity and prophylactic potentials of extract and fractions of Trema orientalis (Linn.) stem bark.

BACKGROUND: Trema orientalis (T. orientalis Linn) has been used in the management of malaria in the western part of Nigeria and despite its application in ethnomedicine, there is dearth of scientific evidence to justify the acclaimed prophylactic antimalarial usage of the plant. The aim of this study is to assess the in vitro antiplasmodial cell-free assay and chemopreventive efficacy of the methanol extract of the stem bark of T. orientalis and its fractions as a prophylactic regimen for malaria prevention. Also, the antimicrobial activities of the extract and the fractions were investigated. METHOD: Vacuum liquid chromatography was used to obtain dichloromethane, ethylacetate and methanol fractions from the methanol extract of T. orientalis. The fractions were tested for their prophylactic and cell-free antimalarial activity using murine models and ß-hematin formation assay respectively. Disc diffusion method was used to determine the antibacterial activity of the extract and its fractions against both Gram-positive and Gram-negative bacteria. RESULTS: In the prophylactic experiment, dichloromethane (DCMF), methanol fraction (MF) and extract (ME) (in this order) showed significant chemopreventive effects against P. berghei invasion of the red blood cells when compared with both Sulfadoxine-Pyrimethamine (SP) and untreated controls. Results of the in vitro study showed that the DCMF had the highest effect in preventing the formation of ß-hematin when compared with other fractions. The DCMF also had the highest percentage inhibition of ß-hematin formation when compared with chloroquine. The extract and fractions showed a concentration dependent antibacterial activity. Methanol extract had a pronounced inhibitory effect on Enterobacter cloaca ATCC 13047 and Enterococcus faecalis ATCC 29212. Serratia mercescens ATCC 9986 and Pseudomonas aeruginosa ATCC 19582 were the most susceptible bacteria. CONCLUSION: The results obtained showed that both extract and fractions of T. orientalis possessed antiplasmodial and antimicrobial activity.

Effects of organic extracts and their different fractions of five Bangladeshi plants on in vitro thrombolysis.

BACKGROUND: The increasingly high incidence of ischemic stroke caused by thrombosis of the arterial vessels is one of the major factors that threaten people's health and lives in the world. The present treatments for thrombosis are still unsatisfactory. Herbal preparations have been used since ancient times for the treatment of several diseases. The aim of this study was to investigate whether herbal preparations possess thrombolytic activity or not. METHODS: An in vitro thrombolytic model was used to check the clot lysis effect of the crude extracts and fractions of five Bangladeshi plant viz., Trema orientalis L., Bacopa monnieri L., Capsicum frutescens L., Brassica oleracea L. and Urena sinuata L. using streptokinase as a positive control and water as a negative control. Briefly, venous blood drawn from twenty healthy volunteers was allowed to form clots which were weighed and treated with the test plant materials to disrupt the clots. Weight of clot after and before treatment provided a percentage of clot lysis. RESULTS: Using an in vitro thrombolytic model, different fractions of five Bangladeshi medicinal plants namely T. orientalis, B. monnieri, C. frutescens, B. oleracea and U. sinuata showed various range of clot lysis activity. Chloroform fractions of T. orientalis, B. monnieri, C. frutescens, B. oleracea and U. sinuata showed highest significant (P < 0.05 and P < 0.001) clot lysis activity viz., 46.44 ± 2.44%, 48.39 ± 10.12%, 36.87 ± .27%, 30.24 ± 0.95% and 47.89 ± 6.83% respectively compared with positive control standard streptokinase (80.77 ± 1.12%) and negative control sterile distilled water (5.69 ± 3.09%). Other fractions showed moderate to low clot lysis activity. Order of clot lysis activity was found to be: Streptokinase > Chloroform fractions > Methanol (crude) extract > Hydro-methanol fractions > Ethyl acetate fractions > n-hexane fractions > Water. CONCLUSIONS: Our study suggests that thrombolytic activity of T. orientalis, B. monnieri and U. sinuata could be considered as very promising and beneficial for the Bangladeshi traditional medicine. Lower effects of other extracts might suggest the lack of bio-active components and/or insufficient quantities in the extract. In vivo clot dissolving property and active component(s) of T. orientalis and B. monnieri for clot lysis could lead the plants for their therapeutic uses. However, further work will establish whether or not, chloroform soluble phytochemicals from these plants could be incorporated as a thrombolytic agent for the improvement of the patients suffering from atherothrombotic diseases.

Mosquito larvicidal potential of four common medicinal plants of India.

BACKGROUND & OBJECTIVES: Mosquitoes transmit serious human health diseases, causing millions of deaths every year. Plants may be sources of alternative mosquito control agents. The present study was carried out to assess the role of larvicidal activities of the crude extracts of four plants viz. Alternanthera sessilis L. (Amaranthaceae), Trema orientalis L. (Cannabaceae), Gardenia carinata Smith. (Rubiaceae) and Ruellia tuberosa L. (Acanthaceae) against Culex quinquefasciatus Say in laboratory bioassay. METHODS: Selective concentrations (0.5, 1 and 1.5%) of crude extract of all four plant leaves were tested against I st to IV th instar larvae of Cx. quinquefasciatus. Log probit analysis (at 95% confidence level) revealed the LC50 values. Preliminary qualitative phytochemical analyses of crude extracts were also done. The lethal concentrations (%) of crude extracts at 24 h against III rd instar larvae were also studied on non-target organisms. RESULT: In a 72 h bioassay experiment with crude extract, the highest mortality was recorded in 1.5 per cent extract. A. sessilis showed the highest mortality (76.7%) at 1.5 per cent crude extract against II nd instar larvae having LC50 value of 0.35 per cent, followed by R. tuberosa (LC50 = 1.84%), G. carinata (LC50 = 2.11) and T. orientalis (LC50 = 2.95%). The regression equation showed a dose-dependent mortality, as the rate of mortality (Y) was positively correlated with the concentration (X). Phytochemical analysis of the crude extract showed the presence of many bioactive phytochemicals such as steroids, alkaloids, terpenes, saponins, etc. No changes in the swimming behaviour and survivality of non-target organism were noticed at the studied concentrations. INTERPRETATION & CONCLUSIONS: Crude extract of the four selected plants showed larvicidal activity against Cx. quinquefasciatus. The extracts at the studied concentrations did not produce any harmful effect on non-target organisms.

Responses to nitrogen pulses and growth under low nitrogen availability in invasive and native tree species with differing successional status.

Invasive species are frequently found in recently disturbed sites. To examine how these disturbance-dependent invasive species exploit resource pulses resulting from disturbance, twelve physiological and morphological traits, including age-dependent responsiveness in leaf traits to nitrogen pulse, were compared between Bischofia javanica, an invasive tree species in Ogasawara islands, and three native Ogasawara species, each having a different successional status. When exposed to a nitrogen pulse, invasive B. javanica showed higher increases in photosynthetic capacity, leaf area, epidermal cell number and cell size in leaves of broad age classes, and root nitrogen absorption ability than two native mid-/late or late-successional species, but showed no particular superiority to a native pioneer species in these responses. Under low nitrogen, however, it showed the largest relative growth rate among the four species, while the native pioneer showed the lowest growth. From these results, we concluded that the combination of moderately high responsiveness to resource pulses and the ability to maintain steady growth under resource limitations may give B. javanica a competitive advantage over a series of native species with different successional status from early to late-successional stages.

ß-sitosterol isolated from the leaves of Trema orientalis (Cannabaceae) promotes viability and proliferation of BF-2 cells.

Trema orientalis is a pioneer species in the cannabis family (Cannabaceae) that is widely distributed in Thai community forests and forest edges. The mature leaves are predominantly used as an anti-parasite treatment and feed for local freshwater fish, inspiring investigation of their phytochemical composition and bioactivity. The purpose of this work was to investigate the bioactive compounds in T. orientalis leaf extract and their cytotoxicity in the BF-2 fish cell line (ATCC CCL-91). Flash column chromatography was used to produce 25 mL fractions with a mixture solvent system comprised of hexane, diethyl ether, methanol, and acetone. All fractions were profiled with HPLC-DAD (mobile phase methanol:aqueous buffer, 60:40 v/v) and UV detection (wavelengths 256 and 365 nm). After drying, a yellowish powder was isolated from lipophilic leaf extract with a yield of 280 µg/g dry weight. Structure elucidation by nuclear magnetic resonance (NMR) indicated it to consist of pure ß-sitosterol. The lipophilic extract and pure compound were evaluated for cytotoxicity using BF-2 cells. MTT assays showed both leaf extract and pure compound at 1 µg/mL to increase cell viability after 24 h treatment. The respective half maximal inhibitory concentration (IC50) values of leaf extract and ß-sitosterol were 7,027.13 and 86.42 µg/ml, indicating a lack of toxicity in the BF-2 cell line. Hence, T. orientalis can serve as a source of non-toxic natural lipophilic compounds that can be useful as bioactive ingredients in supplement feed development.

The putative cannabinoid-secreting trichome of Trema micrantha (L.) Blume (Cannabaceae).

Trema, a genus of the popularly known Cannabaceae, has recently been the subject of cannabinoid bioprospection. T. micrantha is a tree with pharmacological potential widely used in folk medicine. It has two types of glandular trichomes, bulbous and filiform, spread throughout the plant body. Considering the proximity of this species to Cannabis sativa and Trema orientalis, species containing cannabinoids, the glandular trichomes of T. micrantha are also expected to be related to the secretion of these compounds. Thus, this study aims to detail the morphology of secretory trichomes during the synthesis, storing and release of metabolites in T. micrantha. We tested the proposition that they could be a putative type of cannabinoid-secreting gland. Pistillate and staminate flowers and leaves were collected and processed for ontogenic, histochemical, and ultrastructural analyses. Both types of glandular trichomes originate from a protodermal cell. They are putative cannabinoid-secreting sites because: (1) terpene-phenols and, more specifically, cannabinoids were detected in situ; (2) their secretory subcellular apparatus is consistent with that found in C. sativa: modified plastids, polyribosomes, an extensive rough endoplasmic reticulum, and a moniliform smooth endoplasmic reticulum. Plastids and smooth endoplasmic reticulum are involved in the synthesis of terpenes, while the rough endoplasmic reticulum acts in the phenolic synthesis. These substances cross the plasma membrane by exocytosis and are released outside the trichome through cuticle pores. The study of the cell biology of the putative cannabinoid glands can promote the advancement of prospecting for natural products in plants.

Pneumotoxicosis in sheep caused by ingestion of trema micrantha.

Trema micrantha, a fast-growing tree distributed throughout the Americas, produces palatable leaves that have been associated with hepatic necrosis and acute death when consumed by livestock. This report describes fatal pulmonary disease of sheep triggered by consumption of Trema micrantha. Affected sheep had severe progressive dyspnea for a few days before death. Subcutaneous and mediastinal emphysema, reddened lungs, interalveolar septal thickening, and diffuse type II pneumocyte proliferation were the main pathological findings. After ingesting 77.5 and 102.5 g/kg (divided in 3 doses, at 30-day intervals) of T. micrantha leaves, 2 additional sheep developed the same condition. These findings indicate that T. micrantha toxicosis should be considered in the differential diagnosis of ovine respiratory disease.

Effect of prescribed fire on soil properties and N transformation in two vegetation types in South China.

Prescribed fire is a common site preparation practice in forest management in southern China. However, the effect of fire on soil properties and N transformations is still poorly understood in this region. In this study, soil properties and N transformations in burned and unburned site of two vegetation types (Eucalyptus plantation and shrubland) were compared in rainy and dry seasons after 2 years' prescribed fire. Soil pH and soil NH4-N were all higher in the burned site compared to the unburned control. Furthermore, burned sites had 30-40 % lower of soil total phosphorus than conspecific unburned sites. There was no difference in soil organic matter, total N, soil exchangeable cations, available P or NO3-N. Nitrogen mineralization rate of 0-5 cm soil in the unburned site ranged from 8.24 to 11.6 mg N kg(-1) soil month(-1) in the rainy season, compared to a lower level of 4.82-5.25 mg N kg(-1) soil month(-1) in the burned sites. In contrast, 0-5 cm layer nitrification rate was overall 2.47 mg N kg(-1) soil month(-1) in the rainy season, and was not significantly affected by burning. The reduced understory vegetation coverage after burning may be responsible for the higher soil NH4-N in the burned site. This study highlights that a better understanding the effect of prescribed burning on soil nutrients cycling would provide a critical foundation for management decision and be beneficial to afforestation in southern China.

Network pharmacology-based anti-pancreatic cancer potential of kaempferol and catechin of Trema orientalis L. through computational approach.

In pancreatic cancer, healthy cells in the pancreas begin to malfunction and proliferate out of control. According to our conventional knowledge, many plants contain several novel bioactive compounds, having pharmaceutical applications for the treatment of disease like pancreatic cancer. The methanolic fraction of fruit extract of Trema orientalis L. (MFETO) was analysed through HRMS. In this in silico study, pharmacokinetic and physicochemical properties of the identified flavonoids from MFETO were screened out by ADMET analysis. Kaempferol and catechin followed Lipinski rules and showed no toxicity in Protox II. Targets of these compounds were taken from SwissTarget prediction and TCMSP whilst targets for pancreatic cancer were taken from GeneCards and DisGeNET databases. The protein-protein interaction (PPI) network of common genes was generated through STRING and then exported to the Cytoscape to get top 5 hub genes (AKT1, SRC, EGFR, TNF, and CASP3). The interaction between compounds and hub genes was analysed using molecular docking, and high binding affinity between them can be visualised by Biovia discovery studio visualizer. Our study shows that, five hub genes related to pancreatic cancer play an important role in tumour growth induction, invasion and migration. Kaempferol effectively check cell migration by inhibiting ERK1/2, EGFR-related SRC, and AKT pathways by scavenging ROS whilst catechin inhibited TNFα-induced activation and cell cycle arrest at G1 and G2/M phases by induction of apoptosis of malignant cells. Kaempferol and catechin containing MFETO can be used for formulation of potent drugs for pancreatic cancer treatment in future.

Distribution of the herbicide atrazine in a microcosm with riparian forest plants.

Pesticides applied on sugarcane reach the subsoil of riparian forests and probably contaminate the river water. This work was conducted to learn about the phytoremediation of atrazine and subsoil contamination using the common riparian forest species of Cecropia hololeuca Miq. and Trema micranta (L.) Blum. These plants were grown in soil microcosms where (14)C-atrazine at 1/10 of the field-recommended dose was applied at the bottom of the microcosm simulating the movement from contaminated ground water to the upper soil layers and into plants. Residues of (14)C-atrazine were detected in all parts of the microcosm including soil, rhizosphere and the roots in different layers of the microcosm, stem and leaves. Atrazine mineralization was higher (10.2%) in the microcosms with plants than the control microcosms without plants (1.2%). The upward movement of this pesticide from deeper to more superficial soil layers occurred in all the microcosms with plants, powered by evapotranspiration process. From the atrazine applied in this study about 45% was taken up by C. hololeuca and 35% by T. micrantha. The highest amount of radioactivity (%) was found in the fine roots and the specific radioactivity (% g(-1)) showed that thick, fine roots and leaves bioaccumulate atrazine. The enhanced mineralization of atrazine as well the phytostabilization effect of the tree biomass will reduce the bioavailability of these residues and consequently decrease the hazardous effects on the environment.

SilicoDArT and SNP markers for genetic diversity and population structure analysis of Trema orientalis; a fodder species.

Establishing the genetic diversity and population structure of a species can guide the selection of appropriate conservation and sustainable utilization strategies. Next-generation sequencing (NGS) approaches are increasingly being used to generate multi-locus data for genetic structure determination. This study presents the genetic structure of a fodder species -Trema orientalis based on two genome-wide high-throughput diversity array technology (DArT) markers; silicoDArT and single nucleotide polymorphisms (SNPs). Genotyping of 119 individuals generated 40,650 silicoDArT and 4767 SNP markers. Both marker types had a high average scoring reproducibility (>99%). Genetic relationships explored by principal coordinates analysis (PCoA) showed that the first principal coordinate axis explained most of the variation in both the SilicoDArT (34.2%) and SNP (89.6%) marker data. The average polymorphic information content did not highly differ between silicoDArT (0.22) and SNPs (0.17) suggesting minimal differences in informativeness in the two groups of markers. The, mean observed (Ho) and expected (He) heterozygosity were low and differed between the silicoDArT and SNPs respectively, estimated at Ho = 0.08 and He = 0.05 for silicoDArT and Ho = 0.23 and He = 0.19 for SNPs. The population of T. orientalis was moderately differentiated (FST = 0.20-0.53) and formed 2 distinct clusters based on maximum likelihood and principal coordinates analysis. Analysis of molecular variance revealed that clusters contributed more to the variation (46.3-60.8%) than individuals (32.9-31.2%). Overall, the results suggest a high relatedness of the individuals sampled and a threatened genetic potential of T. orientalis in the wild. Therefore, genetic management activities such as ex-situ germplasm management are required for the sustainability of the species. Ex-situ conservation efforts should involve core collection of individuals from different populations to capture efficient diversity. This study demonstrates the importance of silicoDArT and SNP makers in population structure and genetic diversity analysis of Trema orientalis, useful for future genome wide studies in the species.

Crystal structures of Parasponia and Trema hemoglobins: differential heme coordination is linked to quaternary structure.

Hemoglobins from the plants Parasponia andersonii (ParaHb) and Trema tomentosa (TremaHb) are 93% identical in primary structure but differ in oxygen binding constants in accordance with their distinct physiological functions. Additionally, these proteins are dimeric, and ParaHb exhibits the unusual property of having different heme redox potentials for each subunit. To investigate how these hemoglobins could differ in function despite their shared sequence identity and to determine the cause of subunit heterogeneity in ParaHb, we have measured their crystal structures in the ferric oxidation state. Furthermore, we have made a monomeric ParaHb mutant protein (I43N) and measured its ferrous/ferric heme redox potential to test the hypothesized link between quaternary structure and heme heterogeneity in wild-type ParaHb. Our results demonstrate that TremaHb is a symmetric dimeric hemoglobin similar to other class 1 nonsymbiotic plant hemoglobins but that ParaHb has structurally distinct heme coordination in each of its two subunits that is absent in the monomeric I43N mutant protein. A mechanism for achieving structural heterogeneity in ParaHb in which the Ile(101(F4)) side chain contacts the proximal His(105(F8)) in one subunit but not the other is proposed. These results are discussed in the context of the evolution of plant oxygen transport hemoglobins, and other potential functions of plant hemoglobins.

Trema and parasponia hemoglobins reveal convergent evolution of oxygen transport in plants.

All plants contain hemoglobins that fall into distinct phylogenetic classes. The subset of plants that carry out symbiotic nitrogen fixation expresses hemoglobins that scavenge and transport oxygen to bacterial symbiotes within root nodules. These "symbiotic" oxygen transport hemoglobins are distinct in structure and function from the nonoxygen transport ("nonsymbiotic") Hbs found in all plants. Hemoglobins found in two closely related plants present a paradox concerning hemoglobin structure and function. Parasponia andersonii is a nitrogen-fixing plant that expresses a symbiotic hemoglobin (ParaHb) characteristic of oxygen transport hemoglobins in having a pentacoordinate ferrous heme iron, moderate oxygen affinity, and a relatively rapid oxygen dissociation rate constant. A close relative that does not fix nitrogen, Trema tomentosa, expresses hemoglobin (TremaHb) sharing 93% amino acid identity to ParaHb, but its phylogeny predicts a typical nonsymbiotic hemoglobin with a hexacoordinate heme iron, high oxygen affinity, and slow oxygen dissociation rate constant. Here we characterize heme coordination and oxygen binding in TremaHb and ParaHb to investigate whether or not two hemoglobins with such high sequence similarity are actually so different in functional behavior. Our results indicate that the two proteins resemble nonsymbiotic hemoglobins in the ferric oxidation state and symbiotic hemoglobins in the ferrous oxidation state. They differ from each other only in oxygen affinity and oxygen dissociation rate constants, two factors key to their different functions. These results demonstrate distinct mechanisms for convergent evolution of oxygen transport in different phylogenetic classes of plant hemoglobins.

Response to dehydration and irrigation in invasive and native saplings: osmotic adjustment versus leaf shedding.

To clarify the mechanism underlying successful invasion by tree species into xeric sites on Japan's Bonin Islands, we compared the water use of an alien species, Psidium cattleianum, which is rapidly expanding on ridge sites with shallow soil, with that of a native species, Trema orientalis. We hypothesized that there is a trade-off between leaf shedding with low cavitation resistance (frequent xylem cavitation plus refilling ability) and leaf osmotic adjustment with high cavitation resistance (cessation of xylem cavitation plus canopy leaf retention), indicating contrasting strategies for drought tolerance and water use in semi-arid regions. We examined leaf turnover, leaf gas exchange, leaf water potential and water distribution in stem xylem conduits using cryo-scanning electron microscopy for the saplings of both species under three cycles of artificial drought and sudden pulse irrigation. Invasive P. cattleianum saplings were highly resistant to cavitation in stem xylem conduits, retained their leaves and exhibited effective leaf osmotic adjustment under the drought treatment. In contrast, native T. orientalis saplings exhibited xylem cavitation, conspicuous leaf shedding and less effective leaf osmotic adjustment under the drought treatment. Leaf gas exchange rate recovered more rapidly in P. cattleianum saplings than in T. orientalis saplings immediately following pulse irrigation after a period without irrigation, especially in the first drought cycle. Embolized conduits in T. orientalis were refilled by pulse irrigation, and leaf gas exchange rate recovered following refilling. The two tree species showed contrasting strategies for drought tolerance and water use along a trade-off axis. Cavitation avoidance and effective leaf osmotic adjustment in P. cattleianum saplings under drought conditions partially support their survival at the xeric ridge sites on the Bonin Islands. Our results help to explain the success of P. cattleianum in its invasion of a sub-arid environment.

Trema micrantha toxicity in horses in Brazil.

After ingesting green leaves of T. micrantha, 2 horses showed apathy, locomotor deficit, blindness, recumbency, paddling, coma and death. The main gross findings were scattered haemorrhages, enhanced lobular pattern of the liver, and cerebral oedema. Histological changes included disseminated haemorrhages, massive hepatocellular necrosis, neuronal degeneration, Alzheimer type II astrocytes and cerebral perivascular oedema. Clinicopathological findings which were comparable with those observed in Trema micrantha poisoned ruminants, associated with epidemiological evidence suggested the diagnosis.Trema micrantha poisoning should be evaluated as a possible cause in the diagnosis of equine hepatopathy and occasional secondary encephalopathy.

Long-term persistence of pioneer species in tropical rain forest soil seed banks.

In tropical forests, pioneer tree species regenerate from seeds dispersed directly into canopy gaps and from seeds that persisted in soil seed banks before gap formation. Life-history models have suggested that selection for the long-term persistence of tree seeds in the soil should be weak because persistence potentially reduces population growth rate by extending generation time and because adult life spans may exceed the return interval of favorable recruitment sites. Here we use accelerator mass spectrometry to carbon-date seeds of three pioneer tree species extracted from undisturbed seed banks in seasonally moist lowland Neotropical forest. We show that seeds of Croton billbergianus, Trema micrantha, and Zanthoxylum ekmannii germinate successfully from surface soil microsites after 38, 31, and 18 years, respectively. Decades-long persistence may be common in large-seeded tropical pioneers and appears to be unrelated to specific regeneration requirements.

Initial hydraulic failure followed by late-stage carbon starvation leads to drought-induced death in the tree Trema orientalis.

Drought-induced tree death has become a serious problem in global forest ecosystems. Two nonexclusive hypotheses, hydraulic failure and carbon starvation, have been proposed to explain tree die-offs. To clarify the mechanisms, we investigated the physiological processes of drought-induced tree death in saplings with contrasting Huber values (sapwood area/total leaf area). First, hydraulic failure and reduced respiration were found in the initial process of tree decline, and in the last stage carbon starvation led to tree death. The carbohydrate reserves at the stem bases, low in healthy trees, accumulated at the beginning of the declining process due to phloem transport failure, and then decreased just before dying. The concentrations of non-structural carbohydrates at the stem bases are a good indicator of tree damage. The physiological processes and carbon sink-source dynamics that occur during lethal drought provide important insights into the adaptive measures underlying forest die-offs under global warming conditions.

Trema orientalis (Linn.) leaves promotes anticancer activity in Ehrlich ascites carcinoma (EAC) in Swiss albino mice.

Background The in vivo anticancer effect of the Trema orientalis leaves crude methanol extract (TLME) was screened against Ehrlich ascites carcinoma (EAC) in Swiss albino mice. Materials and methods The cytotoxic activity of TLME was determined in vitro by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The growth inhibitory activity and morphological alterations were determined by the hemocytometer counting of the EAC cells using trypan blue dye. The apoptotic cells were assessed by DAPI (4',6-diamidino-2-phenylindole) staining. The hematological and biochemical parameters of experimental mice were also estimated. Results After treatment with the TLME, the viable tumor cell count, morphological changes and nuclear damages of the EAC cells were observed along with the hematological parameters of the experimental mice. The LD50 of TLME was 3120.650 mg/kg body weight, and this extract was proven to be safe at a dose of as high as 800 mg/kg body weight. The oral administration of the TLME at 400 mg/kg body weight resulted in approximately 59% tumor cell growth inhibition compared with the control mice, with considerable apoptotic features, including membrane blebbing, chromatin condensation, nuclear fragmentation and aggregation of the apoptotic bodies in DAPI staining under a fluorescence microscope. The TLME also dose-dependently restored the altered hematological parameters to approximately normal levels. The TLME exhibited bolstering cytotoxic effect against the EAC cell with the IC50 value of 29.952 ± 1.816 µg/mL. Conclusion The TLME has potential as a natural anti-cancer product with apoptosis induction property and cytotoxicity against carcinoma cells.

Neurotoxicosis in horses associated with consumption of Trema micrantha.

BACKGROUND: Trema micrantha is a tree widely distributed throughout the Americas. The tree produces highly palatable leaves that have been associated with natural poisoning in goats, sheep and horses, in which hepatic necrosis and hepatic encephalopathy have been observed. OBJECTIVES: This study describes malacia and haemorrhage in the central nervous system (CNS) due to T. micrantha consumption, with minimal to absent hepatic lesions. STUDY DESIGN: Retrospective case series. METHODS: A total of 14 horses with a history of neurological signs and spontaneous consumption of T. micrantha leaves were submitted to necropsy and multiple samples were collected for histopathology. Details of clinical history and signs of the horses were obtained through inquiries to the owners and attending veterinarians. RESULTS: All the 14 horses had neurological signs of ataxia, severe sialorrhoea, involuntary running movements, sternal and lateral recumbency, and death after a clinical course that lasted from 24 h to 9 days. For a few days prior to onset of clinical signs, all horses had spontaneously consumed, potentially toxic doses of T. micrantha leaves. All 14 brains had diffuse yellowish discoloration affecting the rhombencephalon, mesencephalon, diencephalon, telencephalon and corpus striatum. In all cases, the most severe lesions were observed in the pons. Spinal cord lesions were observed affecting the lumbar intumescence, which was swollen with darken and depressed areas at the dorsal and ventral horns, and at the sacral level, which on cut surface displayed a friable and yellowish grey matter. The lesions observed grossly in brain and spinal cord consisted microscopically of severe vasculitis and liquefactive necrosis of white and grey matter of the brainstem, cerebellum and spinal cord. MAIN LIMITATIONS: This is a small retrospective series relying on clinical observations reported by owners and attending veterinarians. The mechanism of action of the plant toxin in the CNS is still unidentified. CONCLUSION: T. micrantha poisoning in horses causes predominantly a neurological disease, with minimal to absent hepatic lesions.