Morpho-anatomical features of underground systems in six Asteraceae species from the Brazilian Cerrado

In the Brazilian Cerrado (neotropical savanna), the development of bud-bearing underground systems as adaptive structures to fire and dry periods can comprise an important source of buds for this ecosystem, as already demonstrated in the Brazilian Campos grasslands and North American prairies. Asteraceae species from both woody and herbaceous strata have subterranean organs that accumulate carbohydrates, reinforcing the adaptive strategy of these plants to different environmental conditions. This study aims to analyse the morpho-anatomy of underground systems of six species of Asteraceae (Mikania cordifolia L.f. Willd., Mikania sessilifolia DC, Trixis nobilis (Vell.) Katinas, Pterocaulon alopecuroides (Lam.) DC., Vernonia elegans Gardner and Vernonia megapotamica Spreng.), to describe these structures and to verify the occurrence and origin of shoot buds, and to analyse the presence of reserve substances. Individuals sampled in Cerrado areas in São Paulo State showed thick underground bud-bearing organs, with adventitious or lateral roots and presence of fructans. Xylopodium was found in all studied species, except for Trixis nobilis, which had stem tuber. The presence of fructans as reserve, and the capacity of structures in the formation of buds indicate the potential of herbaceous species of Asteraceae in forming a viable bud bank for vegetation regeneration in the Brazilian Cerrado.

Screening of Asteraceae (Compositae) Plant Extracts for Larvicidal Activity against Aedes fluviatilis (Diptera: Culicidae)

Ethanol extracts of 83 plants species belonging to the Asteraceae (Compositae) family, collected in the State of Minas Gerais, Brazil, were tested for larvicidal activity against the mosquito Aedes fluviatilis - Diptera: Culicidae). The extract from Tagetes minuta was the most active with a LC90 of 1.5 mg/l and LC50 of 1.0 mg/l. This plant has been the object of several studies by other groups and its active components have already been identified as thiophene derivatives, a class of compounds present in many Asteraceae species. The extract of Eclipta paniculata was also significantly active, with a LC90 of 17.2 mg/l and LC50 of 3.3 mg/l and no previous studies on its larvicidal activity or chemical composition could be found in the literature. Extracts of Achryrocline satureoides, Gnaphalium spicatum, Senecio brasiliensis, Trixis vauthieri, Tagetes patula and Vernonia ammophila were less active, killing more than 50% of the larvae only at the higher dose tested (100 mg/l).

A new species of Glena Hulst (Lepidoptera, Geometridae) from northern Chile

A new species of Glena Hulst (Lepidoptera, Geometridae) from northern Chile. A new species of Glena Hulst (Lepidoptera, Geometridae) is described from two valleys of the coastal desert of northern Chile. Immature stages are associated with Trixis cacalioides (Kunth) Don. (Asteraceae). Holotype, male and female genitalia, and a sexual dimorphic feature are illustrated. This is the first record of a species of Glena from Chile.

Ocorrência de apomixia e partenocarpia em algumas espécies subtropicais de Asteraceae

Neste trabalho foram estudados os sistemas reprodutivos de 22 espécies de Asteraceae ocorrentes na região de Curitiba, PR, tendo em vista investigar a ocorrência de apomixia em representantes subtropicais desta família. Testes de campo mostraram sete espécies produzindo frutos nos tratamentos de apomixia (Calea hispida, Taraxacum officinale, Baccharis cylindrica, B. dracunculifolia, Chromolaena ivaefolia, Trixis verbasciformis e Vernonia discolor), mas apenas as duas primeiras com sementes viáveis. As demais 15 espécies não produziram frutos nos tratamentos de apomixia: Bidens pilosa, B. tinctoria, Campovassouria cruciata, Chromolaena laevigata, Erechtites valerianaefolia, Hypochoeris radicata, H. tweediei, Lactuca scariola, Mutisia coccinea, Senecio brasiliensis, Sonchus oleraceus, Sphagneticola trilobata, Vernonia platensis e V. flexuosa apresentaram frutos formados em tratamentos de autopolinização espontânea, em níveis extremamente variáveis. Perezia cubataensis foi a única espécie que não apresentou autopolinização espontânea. Testes de viabilidade de pólen mostraram esterilidade muito baixa em todas as espécies (inclusive cinco apomíticas), à exceção de T. officinale e C. ivaefolia. A freqüência relativamente baixa de casos de apomixia entre Asteraceae de clima subtropical é notável, assim como a partenocarpia (produção e desenvolvimento de frutos sem sementes) encontrada em cinco das espécies estudadas .

DAHP synthase from Mycobacterium tuberculosis H37Rv: Cloning, expression, and purification of functional enzyme

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains the leading cause of mortality due to a bacterial pathogen. According to the 2004 Global TB Control Report of the World Health Organization, there are 300,000 new cases per year of multi-drug resistant strains (MDR-TB), defined as resistant to isoniazid and rifampicin, and 79% of MDR-TB cases are now super strains, resistant to at least three of the four main drugs used to treat TB. Thus there is a need for the development of effective new agents to treat TB. The shikimate pathway is an attractive target for the development of antimycobacterial agents because it has been shown to be essential for the viability of M. tuberculosis, but absent from mammals. The M. tuberculosis aroG-encoded 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (mtDAHPS) catalyzes the first committed step in this pathway. Here we describe the PCR amplification, cloning, and sequencing of aroG structural gene from M. tuberculosis H37Rv. The expression of recombinant mtDAHPS protein in the soluble form was obtained in Escherichia coli Rosetta-gami (DE3) host cells without IPTG induction. An approximately threefold purification protocol yielded homogeneous enzyme with a specific activity value of 0.47 U mg-1 under the experimental conditions used. Gel filtration chromatography results demonstrate that recombinant mtDAHPS is a pentamer in solution. The availability of homogeneous mtDAHPS will allow structural and kinetics studies to be performed aiming at antitubercular agents development. © 2004 Elsevier Inc. All rights reserved.