Occurrence of Praxelis clematidea Witches'-Broom Disease Association with 16SrI Group 'Candidatus Phytoplasma asteris' in Hainan Island of China.

Praxelis clematidea is an invasive herbaceous plant belonging to Asteraceae family. From August to November 2020, the plants showing severe witches'-broom symptoms were found in farms and roadsides from Ding'an of Hainan Province, a tropical island of China. The disease symptoms were suggestive of phytoplasma infection. For pathogen detection, P. clematidea samples consisting of six symptomatic and three asymptomatic plants were collected from the farms and roadsites of Ding'an with 40 % incidence by conducting surveys and statistics. Total nucleic acids were extracted using 0.10 g of fresh leaf tissues of the plant through CTAB DNA extraction method. Conserved gene sequences of 16S rRNA and secA genes from phytoplasma were amplified by direct PCR using primer pairs of R16mF2/R16mR1 and secAfor1/secArev3, respectively. R16mF2/R16mR1 PCR amplicons were obtained for all symptomatic samples but not from the symptomless plants. The amplicons were purified and sequenced by Biotechnology (Shanghai) Co., Ltd. (Guangzhou, China). Sequences of 16S rRNA gene (1323 bp) and secA (732 bp) were obtained and all the gene sequences were identical, designated as PcWB (Praxelis clematidea witches'-broom)-hnda. Representative sequencs were deposited in Genbank with accession numbers of PP098736 (16S rDNA) and PP072216 (secA). Nucleotide BLAST (Basic Local Alignment Search Tool) search based on 16S rRNA gene sequences indicated that PcWB-hnda had 100% sequence identity (1323/1323) with 'Candidatus Phytoplasma asteris'-related strains belonging to 16SrI group like Waltheria indica virescence phytoplasma (MW353909) and Capsicum annuum yellow crinkle phytoplasma (MT760793); had 99.62 % sequence identity (1321/1326) with the phytoplasma strains of 16SrI group such as Oenothera phytoplasma (M30790). RFLP (Restriction Fragment Length Polymorphism) pattern derived from 16Sr RNA gene sequences by iPhyClassifier showed identical (similarity coefficient=1.00) to the reference pattern of 16SrI-B subgroup (GenBank accession number: AP006628). The results obtained demonstrate that the phytoplasma strain PcWB-hnda under study is a member of 16SrI-B subgroup. A BLAST search based on secA gene sequences indicated that PcWB-hnda shares 100% sequence identity (732/732 bp) with Pericampylus glaucus witches'-broom phytoplasma (MT875200), 99% sequence identify (728/732 bp) with onion yellows phytoplasma OY-M(AP006628), and 99% sequence identify (729/732 bp) with rapeseed phyllody phytoplasma isolate RP166 (CP055264), among other phytoplasma strains that belong to 16SrI group. Previous studies demonstrated that P. clematidea can be infected by phytoplasmas affiliate to the 16SrII group (GenBank accession number: KY568717 and EF061924) in Hainan Island of China. To our knowledge, this is the first report of a natural infection of P. clematidea by a group 16SrI phytoplasma in the Island of China. 16SrI group can infect agronomic important species such as areca palm in the island and P. clematidea can be a reservoir of 16SrI phytoplasmas. Therefore, it is necessary to search of potential vectors of the pathogens, which would contribute to epidemiological monitoring and prevention of the related diseases.

Sesquiterpenes from two Compositae plants as promising inhibitors to nuclear hormone receptor 3 of Tribolium castaneum.

Essential oils (EOs) and their volatile secondary metabolites have been proved to be effective on storage pests control, while restricted on the application due to unclear mechanism. Molecular dynamics (MD) simulations and binding free energies analysis provided an effective approach to reveal mechanism on conformational calculation. In this work, the insecticidal and repellent capacities of Praxelis clematidea and Ageratum houstonianum oils and their main components identified by gas chromatography-mass spectrometry (GC-MS) were scientifically measured. Interestingly, P. clematidea oil exhibited strong fumigant toxicity against Tribolium castaneum (LC50 = 7.07 mg/L air). Moreover, two EOs exhibited over 80% repellent rate against T. castaneum at the highest concentration of 78.63 nL/cm2. Furthermore, hundreds of enzymes related to the regulation of biological processes of T. castaneum were screened to explore the underlying molecular mechanism and develop promising insecticides. Besides, top hits were subjected to MD simulations and binding free energies analysis to elucidate complex inter-molecular stability and affinity over simulated time. The results demonstrated that isolongifolene, δ-cadinene, ß-caryophyllene and caryophyllene oxide were prioritized as they were establishing conserved and stable interactions with residues of nuclear hormone receptor 3 (TcHR3) of T. castaneum, which suggested that the four sesquiterpenes have potential to be promising insecticides on storage pests control.

Anti-inflammatory phenolics and phenylpropanoids from Praxelis clematidea.

Praxelis clematidea (Asteraceae) is a noxious invasive exotic plant in southern China, and it has caused great damage to ecological conditions and serious financial losses. In this study, four new phenolics (1, 2, 7, 8), and two new phenylpropanoids (3, 4), along with seventeen known compounds were separated and purified from the whole plant of P. clematidea. Their chemical structures were determined by extensive spectroscopic analysis methods. Additionally, the potential inhibitory activities on nitric oxide (NO) production and NF-κB nuclear translocation in LPS-triggered RAW 264.7 macrophages of the isolated compounds were evaluated. Notably, compounds 2, 7, and 8 showed significant inhibitory activities on NO production, and also inhibited the expression of iNOS and COX-2. Furthermore, compounds 2, 7, and 8 effectively suppressed the NF-κB nuclear translocation. These findings suggest that P. clematidea has the potential to be developed and promoted as a treatment for inflammation-related diseases.

Avaliação da citotoxicidade em hemácias de humanos do extrato etanólico de Praxelis clematidea (Griseb.)

Introdução: Espécies da família Asteraceae são conhecidas por apresentarem propriedades aromática, cosmética e terapêutica; tendo diversas pesquisas que evidenciou potencial medicinal dessa família. Dentre as espécies de Asteraceae, está Praxelis clematidea, que é rica em substâncias químicas como flavonoides, terpenóides e esteroides, as quais podem desempenhar uma série de atividades biológicas. Objetivo: Verificar o potencial tóxico do extrato etanólico das folhas de P. clematidea frente à células sanguíneas humanas, afim de determinar a toxicidade teórica dessa espécie. Métodos: Para a realização do teste de atividade citotóxica foram preparadas suspensões sanguíneas dos tipos A, B e O, que posteriormente foram misturadas a concentrações distintas do extrato etanólico por 1 (uma) hora. A hemólise foi quantificada por espectrofotometria em comprimento de onda de 540 nm. Resultados: O extrato etanólico das folhas de P. clematidea em diferentes concentrações apresentou baixa citoxicidade contra os eritrócitos humanos in vitro, enfatizando o produto como uma possível opção viável para a indústria de medicamentos fitoterápicos. No entanto, é importante elucidar que mais estudos in vivo precisam ser realizados para confirmar esse perfil toxicológico do extrato.

SUMMARY Introduction: Species of the Asteraceae family are known to have aromatic, cosmetic and therapeutic properties; having several researches that evidenced medicinal potential of this family. Among the species of Asteraceae, there is Praxelis clematidea, which is rich in chemical substances such as flavonoids, terpenoids and steroids, which can perform a series of biological activities. Aim: To verify the toxic potential of the ethanolic extract of P. clematidea leaves against human blood cells, in order to determine the theoretical toxicity of this species. Method: For the performance of the cytotoxic activity test, blood suspensions of types A, B and O were prepared, which were subsequently mixed at different concentrations of the ethanolic extract for 1 (one) hour. Hemolysis was quantified by spectrophotometry at a wavelength of 540 nm. Results: The ethanolic extract of P. clematidea leaves in different concentrations showed low cytotoxicity against human erythrocytes in vitro, emphasizing the product as a possible viable option for the herbal medicine industry. However, it is important to clarify that more in vivo studies need to be carried out to confirm this toxicological profile of the extract.

Introducción: Se sabe que las especies de la familia Asteraceae tienen propiedades aromáticas, cosméticas y terapéuticas; habiendo varias investigaciones que evidenciaron el potencial medicinal de esta familia. Entre las especies de Asteraceae, se encuentra Praxelis clematidea, que es rica en sustancias químicas como flavonoides, terpenoides y esteroides, que pueden realizar una serie de actividades biológicas. Objetivo: Verificar el potencial tóxico del extracto etanólico de hojas de P. clematidea contra las células sanguíneas humanas, con el fin de determinar la toxicidad teórica de esta especie. Metodos: Para realizar la prueba de actividad citotóxica se prepararon suspensiones de sangre de los tipos A, B y O, que luego se mezclaron a diferentes concentraciones del extracto etanólico durante 1 (una) hora. La hemólisis se cuantificó mediante espectrofotometría a una longitud de onda de 540 nm. Resultados: El extracto etanólico de hojas de P. clematidea a diferentes concentraciones mostró baja citotoxicidad contra eritrocitos humanos in vitro, destacando el producto como una posible opción viable para la industria de la fitoterapia. Sin embargo, es importante aclarar que es necesario realizar más estudios in vivo para confirmar este perfil toxicológico del extracto.

Autonomous apomixis in Praxelis clematidea (Asteraceae: Eupatorieae), an invasive alien plant.

Understanding the reproductive mechanisms of invasive alien species can lay the foundation for effective control measures. Praxelis clematidea is a triploid neotropical Asteraceae species that is invasive in China and other countries. However, few studies have focused on its reproductive biology. In this study, flow cytometric seed screening (FCSS) was used to identify and confirm the reproductive mode of the species. The development of ovules, anthers, and mega- and microgametophytes was observed using a clearing method and differential interference contrast microscopy. Pollen viability was measured using the Benzidine test and Alexander's stain. Pollen morphology was observed via fluorescence microscopy after sectioning the disk florets and staining with water-soluble aniline blue or 4'6-diamidino-2-phenylindole nuclei dyes. Controlled pollination experiments were conducted on four populations in China to examine the breeding system and to confirm autonomous apomixis. The reproductive mode was found to be autonomous apomixis without pseudogamy, according to FCSS. Megaspore mother cells developed directly into eight-nucleate megagametophytes without meiosis, conforming to Antennaria-type diplospory. The unreduced egg cells developed into embryos through parthenogenesis, while the endosperm was formed by the fusion of two unreduced polar nuclei. Pollen viability was very low (0.82 ± 0.57 % and 0.36 ± 0.44 %) as measured by the Benzidine test and Alexander's stain, respectively. The majority of the pollen grains were empty and had neither cytoplasm nor nuclei. The seed set was >90 % for all treatments of open pollination, bagging and emasculated capitula. Mature cypselae developed in capitula that were emasculated before flowering, which confirmed that the breeding system of P. clematidea was autonomous apomixis. The present study is the first report of autonomous apomixis in P. clematidea in China. Antennaria-type autonomous apomixis in P. clematidea greatly increases the probability of successful colonisation and dispersal of P. clematidea into new areas, which likely contributes to its high invasion potential. Effective control measures should be implemented to prevent autonomous (pollen-independent) seed production.

Phytochemical investigation of the flowers of Praxelis clematidea (Griseb.) R.M. King & H. Rob.

Chemical investigations of the flowers of Praxelis clematidea resulted in the isolation of 12 known compounds (1-12). Their structures were elucidated by extensive spectroscopic studies and chemical evidence. The structure and absolute configuration of 1 was precisely determined by a combination of 2 D NMR and quantum chemical calculations of ECD spectra analysis. Compounds 1, 4, 11 were isolated from the genus Praxelis for the first time, while 1-6, 8-12 were isolated from P. clematidea for the first time. The antibacterial activity of compounds 1, 2, 7, 9 were evaluated.

Anti-neuroinflammatory benzofurans and lignans from Praxelis clematidea.

Praxelis clematidea (Asteraceae) is a harmful invasive alien weed, which cause huge destruction of ecological environment and economic losses. In this study, 22 compounds were isolated and purified from the whole plant of P. clematidea, including 4 benzofurans (1-4), 18 lignans (5-22), and five of which were new compounds (1, 3, 4, 9, 10). Various spectroscopic analysis methods were utilized to elucidate their chemical structures. The inhibitory effects of the isolated compounds on NO release from BV-2 microglia cells induced by LPS were investigated. Most of the compounds showed pronounced anti-neuroinflammatory activity. Additionally, the new compounds 3, 4 and 10 exhibited significant anti-neuroinflammatory effects, and the biological activities were further confirmed by immunoblotting, quantitative PCR and immunofluorescence staining assays. As results, this study provided a new idea for the further treatment and utilization of P. clematidea as anti-neuroinflammatory agents in health-benefit products.

Detection and identification of a novel subgroup 16SrII-V phytoplasma associated with Praxelis clematidea phyllody disease.

Praxelis clematidea is a very vigorous non-native weed in tropical and subtropical regions of China. P. clematidea plants showing symptoms of phyllody disease were found in an orchard located in Hainan province, PR China. The presence of phytoplasmas was confirmed by PCR of 16S rRNA gene using phytoplasma universal primers R16mF2/R16mR1 followed by R16F2n/R16R2. According to 16S rRNA gene sequence similarity, the P. clematidea phyllody (PCP) phytoplasma is a 'CandidatusPhytoplasma australasiae'-related strain (99.5 % similarity). The virtual RFLP pattern analyses of 16S rRNA gene sequences indicated that the PCP is a new subgroup within 16 Sr group II. The most similar RFLP pattern is the reference pattern of 16Sr group II, subgroup M, with a similarity coefficient of 0.94. These results were confirmed by phylogenetic analyses of the 16S rRNA gene. These findings suggest that P. clematidea phyllody disease is caused by a new phytoplasma considered to be a novel subgroup, 16SrII-V.

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Community invaded by Praxelis clematidea in karst mountainous area of Pingguo, Guangxi Province was investigated including 4 land types, i.e. abandoned cropland, young plantation, roadside and shrub. Meta analysis, analysis of covariance, linear mixed effect model and recursive partitioning were used to analyze their herb diversity and richness in relation to environmental variables. The results showed that summary effects were positive and significant, effects of groups were positive, effect of abandoned cropland was negative, and effects of other three land types were positive, and shrub had high weight in the analysis. Analysis of covariance indicated that importance value of P. clematidea, distance to driveway and soil were the main numeric factors influencing herb diversity and herb species richness, and plots invaded had higher herb diversity and richness than those uninvaded. Land types had extremely significant impacts on herb diversity but had nothing on herb species richness. Linear mixed effect model partitioned the explained variances of random effects, factor P. clematidea present or absent and residuals respectively contributed 50.9% and 49.1% in Shannon model, while 39.0% and 61.0% in richness model, groups and land types contributed zero to the random effects. P. clematidea invasion could be classified into 5 levels, and modest invasion caused higher herb diversity and richness. When P. clematidea importance value was more than 23.6%, the critical threshold, both herb diversity and richness declined.

Antibacterial activity of flavonoid 5.7.4’-trimethoxyflavone isolated from Praxelis clematides R.M. King & Robinson / Actividad antibacterial del flavonoide 5.7.4’-trimetoxiflavona aislada dePrexelis clematides R.M. King & Robinson

The flavonoids are a large class of polyphenolic compounds found in plants that are known to exhibit biological effects. In the study, the flavonoid 5.7.4’-trimethoxyflavone (TMF) extracted from Praxelis clematidea was evaluated for its antibacterial activity. Microdilution method was used for antibacterial assay of the flavonoid and eleven bacteria strains were used in the study for activities. The results were also compared with the standard drug, Chloramphenicol (100 ug/mL). The results obtained showed activity of the flavonoid against Gram positive and Gram negative bacteria.

Los flavonoides son una clase importante de compuestos polifenólicos encontrados en las plantas que se sabe que presentan efectos biológicos. En el estudio, el flavonoide 5.7.4 '-trimethoxyflavone (TMF) extraído de Praxelis clematidea fue evaluado por su actividad antibacteriana. Se utilizó el método de microdilución para el ensayo antibacteriano del flavonoide y once cepas de bacterias se usaron en el estudio de las actividades. Los resultados se compararon también con el fármaco estándar, Cloranfenicol (100 ug/mL). Los resultados obtenidos mostraron actividad del flavonoide contra bacterias Gram positivas y Gram negativas.