Differential expression after UV-B radiation and characterization of chalcone synthase from the Patagonian hairgrass Deschampsia antarctica.

Deschampsiaantarctica inhabits the maritime territory of Antarctica and South Patagonia. It grows under very harsh environmental conditions. The survival of this species in low freezing temperatures and under high levels of UV-B radiation may constitute some of the most remarkable adaptive plant responses and suggests that this plant possesses genes associated with cold and UV tolerance. Frequently, increased levels of flavonoids have been linked to highly UV-B irradiated plants. Studies examining the biosynthesis of flavonoids in D. antarctica may provide clues to its success in this extreme environment. In this study, we characterized the family of genes encoding chalcone synthase, a key enzyme of the flavonoid biosynthetic pathway. DaCHS was cloned, sequenced and characterized by using software tools. CHS contains two domains, the N-terminal domain ranges from amino acid 8 to 231 and the C-terminal domain ranges from amino acid 241 to 391. Sequence analysis of the three family members revealed a high degree of identity after comparison with other monocotyledons such as Oryza sativa L., Zea mays L. and Hordeum vulgare L. According to these results, DaCHS can be grouped together with H. vulgare CHS1 in the same branch. The phylogenetic tree was built using MEGA software and the neighbour join method with 1000 bootstrap replicates. A model of DaCHS was constructed by way of structural tools and key amino acid residues were identified at the active motif site.

Sesquiterpenes, flavonoids, shikimic acid derivatives and pyrrolizidine alkaloids from Senecio kingii Hook.

Twenty-four compounds including eleven eremophilanolides (1-11), one eremophilane (13), five shikimic acid derivatives (14-18), six flavonoids (19-24), and the macrocyclic unsaturated pyrrolizidine alkaloid integerrimine (25) were isolated from Senecio kingii, an endemic species from the Magallanes Region (Chile). Compounds 3, 5, 6, 8-11 and 13-18 have not been previously reported as natural products. Their molecular structures were determined by NMR spectroscopic analysis and comparison with published NMR data. An X-ray-analysis of compound 3 has been performed. Their insecticidal and antifungal activities were tested, being compound 3 the strongest insect antifeedant. Compounds 6, 9 and 18 were moderate antifungals.

Adaptive variation of Patagonian Senecio patagonicus Hook. & Arn., Adesmia boronioides Hook.F. and Lepidophyllum cupressiforme (Lam.) Cass. as a plant response to environmental stress / Variación adaptativa en respuesta al estrés ambiental de Senecio patagonicus, Adesmia boronioides y Lepidophyllum cupressiforme que habitan en dos localidades de la Patagonia chilena

Different analyses were carried out on the following plant species: Adesmia boronioides Hook.F., Senecio patagonicus Hook. & Arn. and Lepidophyllum cupressiforme (Lam.) Cass. in order to compare the photosynthetic pigment, carotenoid and phenylpropanoid contents. Total phenolic content and antioxidant capacity were measured by using common established reagents: Folin-Ciocalteau and ABTS respectively. Plant samples were collected from specimens growing inside the National Park Pali Aike and the Botanic Garden Carl Skottsberg in Punta Arenas city. The results showed no marked tendencies between photosynthetic pigments. Nevertheless, a good correlation was found among the antioxidant capacity and phenolic compounds. Furthermore, species growing in the Pali Aike National Park seem to be more adapted to the environmental conditions.

Se realizaron diferentes análisis al contenido de pigmentos fotosintéticos, carotenoides y fenilpropanoides. El contenido de fenoles totales y la capacidad antioxidante se midieron usando reactivos ampliamente conocidos: Folin-Ciocalteau y ABTS respectivamente en las siguientes especies: Adesmia boronioides, Senecio patagonicus y Lepidophyllum cupressiforme. Estas plantas se encuentran en el Parque Nacional Pali Aike y en el Jardín Botánico Carl Skottsberg en la ciudad de Punta Arenas. Los resultados no muestran una tendencia clara entre las muestras de pigmentos fotosintéticos. Sin embargo, se pudo observar una buena correlación entre la capacidad antioxidante y el contenido de compuestos fenólicos. Además, aparentemente las especies que crecen en el Parque Nacional Pali Aike están más adaptadas a esas condiciones ambientales.

The recurvatianes: a suite of oxygenated guaiane sesquiterpenes from Perezia recurvata.

Six guaiane sesquiterpenes recurvatiane A-F, including the previously known recurvatiane E and xanthomicrol, were isolated from the Andean Perezia recurvata and their structures determined by spectroscopic evidence. The absolute stereochemistry of recurvatiane A was established by derivatization with (R)- and (S)-α-methoxy-α-phenylacetic acids (MPA). The suite of guaiane-based metabolites here reported, which we have named recurvatianes A-F, provide an example of a pathway by which molecular diversity is generated by the occurrence of specific oxidation reactions in the late biosynthetic steps of the frame structure.

Effects of UV-B radiation in morpho-genetic characters of Gnaphalium luteo-album.

Genetic analyses of Gnaphalium's DNA showed a high degree of polymorphism in UV-B irradiated plants when compared to controls. Among the five tested primers the four ISSR primers selected for this analysis generated a total of 189 fragments. A high proportion of polymorphic bands ranging from 70% to 28% were found using these ISSR markers. Nei and Li similarity indexes [1] were used to evaluate genetic divergence among plants. The dendrograms obtained using these markers efficiently separate plants from different treatments. A linear relationship was observed between UV-B dose and percentage of dissimilarity which may be related to DNA damage caused by the different UV-B treatments.

Pronuciferine N-oxide, a proaporphine N-oxide alkaloid from Berberis coletioides.

Pronuciferine N-oxide (1), a proaporphine N-methyl-N-oxide alkaloid, along with the parent alkaloid pronuciferine (2) were isolated from Berberis coletioides. The structure of the new compound was determined by spectroscopic evidence. Compound 1 is the first naturally occurring proaporphinoid alkaloid with an N-oxide functionality.

Biological activity of some Patagonian plants.

Citotoxicity (inhibition of cell division in fertilized eggs of Loxechinus albus) and general toxicity (using embryos of Artemia salina) of plants belonging to the genera Senecio, Deschampsia, Alstroemeria, Anarthrophyllum, Chloraea and Geranium were investigated.

Effects of UV-B radiation on the Patagonian Jaborosa magellanica Brisben.

Treatment of Jaborosa magellanica with artificial UV-B radiation caused changes in plant growth, plant chemistry and increase DNA polymorphisms. Spectrophotometric analysis showed that UV-B radiation decreases the chlorophylls content, and increases the amount of UV-B absorbing compounds (e.g., phenylpropanoids). Other UV-induced alterations include reduction in leaf area, alterations in plant architecture, and DNA damage. Using random primers and PCR amplification procedure, a high degree of polymorphism was detected when treated plants were compared to non-irradiated plants. These biochemical changes may be interpreted as plant response to UV-B radiation stress and as an indicator of DNA damage.