Desiccation tolerance in the Antarctic moss Sanionia uncinata

BACKGROUND: One of the most extreme environments on our planet is the Maritime Antarctic territory, due to its low-water availability, which restricts the development of plants. Sanionia uncinata Hedw. (Amblystegiaceae), the main colonizer of the Maritime Antarctic, has effective mechanisms to tolerate this environment. It has been described that the tolerance to desiccation is mediated by the hormone abscisic acid (ABA), antioxidants systems, accumulation of compatible solutes and proteins of the late embryogenesis abundant (LEA). However, to date, these mechanisms have not been described in S. uncinata. Therefore, in this work, we postulate that the tolerance to desiccation in the Antarctic moss S. uncinata is mediated by the accumulation of ABA, the osmolytes proline and glycine betaine, and dehydrins (an LEA class 11 proteins). To demonstrate our hypothesis, S. uncinata was subjected to desiccation for 24 h (loss in 95% of water content), and the effects on its physiological, photosynthetic, antioxidant and biochemical parameters were determined. RESULTS: Our results showed an accumulation of ABA in response to water loss, and the activation of protective responses that involves an increment in levels of proline and glycine betaine, an increment in the activity of antioxidant enzymes such as SOD, CAT, APX and POD, and the accumulation of dehydrins proteins. CONCLUSION: The results showed, suggest that S. uncinata is a desiccation-tolerant moss, property mediated by high cellular plasticity regulated by ABA.

Copper stress induces antioxidant responses and accumulation of sugars and phytochelatins in Antarctic Colobanthus quitensis (Kunth) Bartl

BACKGROUND: In field, C. quitensis Is subjected to many abiotic extreme environmental conditions, such as low temperatures, high UV-B, salinity and reduced water potentials, but not metal or metalloid high concentrations in soil, however, other members of Caryophyllaceae family have tolerance to high concentrations of metals, this is the case of Silene genre. In this work, we hypothesize that C. quitensis have the same mechanisms of Silene to tolerate metals, involving accumulation and induction of antioxidant systems, sugar accumulation and the induction of thiols such as phytochelatins to tolerate. RESULTS: The results showing an effective antioxidant defensive machinery involving non-enzymatic antioxidants such as phenolics, GSH and ascorbic acid, in another hand, GSH-related oligomers (phytochelatins) and sugars was induced as a defensive mechanism. CONCLUSIONS: Colobanthus quitensis exhibits certain mechanisms to tolerate copper in vitro demonstrating its plasticity to tolerate several abiotic stress conditions.

Soluble carbohydrate content variation in Sanionia uncinata and Polytrichastrum alpinum, two Antarctic mosses with contrasting desiccation capacities

BACKGROUND: Cryptogamic vegetation dominates the ice-free areas along the Antarctic Peninsula. The two mosses Sanionia uncinata and Polytrichastrum alpinum inhabit soils with contrasting water availability. Sanionia uncinata grows in soil with continuous water supply, while P. alpinum grows in sandy, non-flooded soils. Desiccation and rehydration experiments were carried out to test for differences in the rate of water loss and uptake, with non-structural carbohydrates analysed to test their role in these processes. RESULTS: Individual plants of S. uncinata lost water 60 % faster than P. alpinum; however, clumps of S. uncinata took longer to dry than those of P. alpinum (11 vs. 5 h, respectively). In contrast, rehydration took less than 10 min for both mosses. Total non-structural carbohydrate content was higher in P. alpinum than in S. uncinata, but sugar levels changed more in P. alpinum during desiccation and rehydration (60-50 %) when compared to S. uncinata. We report the presence of galactinol (a precursor of the raffinose family) for the first time in P. alpinum. Galactinol was present at higher amounts than all other non-structural sugars. CONCLUSIONS: Individual plants of S. uncinata were not able to retain water for long periods but by growing and forming carpets, this species can retain water the longest. In contrast individual P. alpinum plants required more time to lose water than S. uncinata, but as moss cushions they suffered desiccation faster than the later. On the other hand, both species rehydrated very quickly. We found that when both mosses lost 50 % of their water, carbohydrates content remained stable and the plants did not accumulate non-structural carbohydrates during the desiccation prosses as usually occurs in vascular plants. The raffinose family oligosaccarides decreased during desiccation, and increased during rehydration, suggesting they function as osmoprotectors.

Effect of aluminum on antioxidant activity and phenolic compounds content in in vitro cultured blueberries / Efectos de aluminio en la capacidad antioxidante y en el contenido de compuestos fenólicos en plántulas de arándano cultivadas in vitro

Blueberry is a popular natural food product consumed worldwide. Acid soils are found throughout the world. A significant problem of acid soils is the active aluminum content, which may result toxic to plant. The present study was undertaken to assess the toxicities of Al for Blueberry (Vaccinium corymbosum L.) cultivated in vitro and treated with 100 and 200 uM Al. The effects of Al concentration on malondialdehyde (MDA) content, antioxidant activity and phenolic compounds of blueberry after 7, 14 and 21 days of treatment were established. The analysis of the MDA accumulated in the tissues of the blueberry seedlings indicates that Al concentration increases the damage caused by lipid peroxidation, for both treatments, after 14 days. The highest antioxidant activity in the extracts was observed at 200 uM Al after 14 days of treatment, being chlorogenic and ellagic acids the most significant metabolites involved in the antioxidant properties. Then, the content of Al in soil could be modulate the content of bioactive compounds in blueberry plants.

El Arándano es un popular alimento natural consumido en todo el mundo. Los suelos ácidos se encuentran en todo el mundo. Un problema significativo de suelos ácidos es el contenido de aluminio activo, que puede resultar tóxico para la planta. Este estudio se realizó para evaluar la toxicidad del aluminio en plantas de arandano, cultivadas in vitro y tratadas con 100 y 200 mM de Al. Se establecieron los del aluminio en el contenido de malodialdehido (MDA), capacidad antioxidante y contenido de compuestos fenolicos en plantulas de arandano luego de 7, 14 y 21 dias de tratamiento. El análisis del MDA acumulado en los tejidos de las plantulas de arándanos indica que la concentración de Al aumenta el daño causado medido como peroxidación de lípidos, para ambos tratamientos, después de 14 días. La actividad antioxidante más alta de los extractos se obseva a 200 mM de Al después de 14 días de tratamiento, siendo los ácidos clorogénico y elágico los metabolitos más importantes que participan en las propiedades antioxidantes. Entonces, el contenido de Al en el suelo podría modular el contenido de compuestos bioactivos en plantas de arándanos, alterando sus propiedades medicinales.

Production of phenolic metabolites by Deschampsia antarctica shoots using UV-B treatments during cultivation in a photobioreactor

Deschampsia antarctica (DA), the only species in the Gramineae family endemic to the Antarctic territory, is characterized by a combination of high levels of free endogenous phenylpropanoid compounds under normal in situ and in vitro growth conditions. In this article, we describe the design and use of a specific temporary immersion photobioreactor to produce both increased DA biomass and secondary metabolite accumulation by UV-B elicitation during cultivation. Three min-long immersions in an induction medium applied every 4 hrs at 14ºC +/- 1 and 20/4 hrs light/darkness photoperiod increased DA biomass production over previous in vitro reports. Biomass duplication was obtained at day 10.7 of culturing, and maximum total phenolics and antioxidant activity were observed after 14 day of culturing. The addition of UV-B radiation pulses for 0.5 hrs at 6 hrs intervals increased total phenolics and antioxidant activity more than 3- and 1.5- fold, respectively, compared to controls with no UV-B. Significant accumulation of scopoletin, chlorogenic acid, gallic acid and rutin was found in these plantlets. This is the first bioreactor designed to optimize biomass and phenylpropanoid production in DA.