Impact of polyploidy on plant tolerance to abiotic and biotic stresses.

Polyploidy, defined as the coexistence of three or more complete sets of chromosomes in an organism's cells, is considered as a pivotal moving force in the evolutionary history of vascular plants and has played a major role in the domestication of several crops. In the last decades, improved cultivars of economically important species have been developed artificially by inducing autopolyploidy with chemical agents. Studies on diverse species have shown that the anatomical and physiological changes generated by either natural or artificial polyploidization can increase tolerance to abiotic and biotic stresses as well as disease resistance, which may positively impact on plant growth and net production. The aim of this work is to review the current literature regarding the link between plant ploidy level and tolerance to abiotic and biotic stressors, with an emphasis on the physiological and molecular mechanisms responsible for these effects, as well as their impact on the growth and development of both natural and artificially generated polyploids, during exposure to adverse environmental conditions. We focused on the analysis of those types of stressors in which more progress has been made in the knowledge of the putative morpho-physiological and/or molecular mechanisms involved, revealing both the factors in common, as well as those that need to be addressed in future research.

Beyond Arabidopsis: Differential UV-B Response Mediated by UVR8 in Diverse Species.

Ultraviolet-B radiation (UV-B, 280-315 nm) is an important environmental signal that regulates growth and development in plants. Two dose-dependent UV-B response pathways were described in plants: a specific one, mediated by UVR8 (the specific UV-B receptor) and an unspecific one, activated by the oxidative damage produced by radiation. The constitutively expressed receptor appears inactive as a dimer, with the two monomers dissociating upon UV-B irradiation. The monomer then interacts with COP1, an ubiquitin ligase, hindering its ability to poly-ubiquitinate transcriptional factor HY5, thus averting its degradation and activating the photomorphogenic response. HY5 induces the synthesis of proteins RUP1 and RUP2, which interact with UVR8, releasing COP1, and inducing the re-dimerization of UVR8. This mechanism has been thoroughly characterized in Arabidopsis, where studies have demonstrated that the UVR8 receptor is key in UV-B response. Although Arabidopsis importance as a model plant many mechanisms described in this specie differ in other plants. In this paper, we review the latest information regarding UV-B response mediated by UVR8 in different species, focusing on the differences reported compared to Arabidopsis. For instance, UVR8 is not only induced by UV-B but also by other agents that are expressed differentially in diverse tissues. Also, in some of the species analyzed, proteins with low homology to RUP1 and RUP2 were detected. We also discuss how UVR8 is involved in other developmental and stress processes unrelated to UV-B. We conclude that the receptor is highly versatile, showing differences among species.

Traditional uses, conservation status and biotechnological advances for a group of aromatic / medicinal native plants from America / Usos tradicionales, estado de conservación y avances biotecnológicos para un grupo de plantas aromáticas / medicinales nativas de América

Medicinal and aromatic plants are biologically and economically valuable species because of their intrinsic value as plants, ability to produce secondary metabolites, possible use in the pharmaceutical and food industries, germplasm availability and applications in traditional medicine. In addition, they hold social and economic importance due to the ancestral knowledge they represent and because they are part of the livelihood of many families. Most of them are collected from the wild and are in serious danger of extinction. Through biotechnological tools it is possible to develop their germplasm and obtain new and improved varieties from wild material, while advocating the alternative of production by cultivation instead of extracting it from nature. The objective of this review is to provide an updated perspective on the traditional uses, conservation status and biotechnological advances in a group of 30 plant species native to the American continent.

Las plantas medicinales y aromáticas deben ser valoradas tanto por su valor intrínseco como tales, por su capacidad de producir metabolitos secundarios, su posible uso en las industrias farmacéutica y alimentaria y por sus aplicaciones en medicina tradicional. Además, tienen importancia social y económica debido al conocimiento ancestral que representan y porque son parte del sustento de muchas familias. La mayoría de estas especies son recolectadas de la naturaleza y están en grave peligro de extinción. A través de herramientas biotecnológicas es posible desarrollar su germoplasma y obtener variedades nuevas y mejoradas a partir de material silvestre; esta estrategia propicia la alternativa de producción por cultivo en lugar de extraerla de la naturaleza. El objetivo de esta revisión es proporcionar una perspectiva actualizada de los usos tradicionales, el estado de conservación y los avances biotecnológicos en un grupo de 30 especies de plantas nativas del continente americano.

Salvadora persica agro-ecological suitability for oil production in Argentine dryland salinity.

One of the major causes of crop stress is soil or water salinity. Thus, selection of the best species for cultivation in semiarid and arid climates is fundamental. Salvadora persica is an evergreen perennial halophyte that can grow under extreme conditions, from very dry environments to highly saline soils. Based on international bibliography, the authors outlined an agro-ecological zoning model to determine the potential cultivation zones for S. persica in Argentina. This model may be applied to any part of the world, using the agro-ecological limits presented in this work. All the maps were developed by the implementation of a geographic information system (GIS) that can be updated by the further incorporation of complementary information, with the consequent improvement of the original database. The overlap of the agroclimatic suitability map on the drylands' saline soils and the drylands' alkaline soils maps, determined the agro-ecological zoning. Since some areas in the agro-ecological zoning can overlap with land that is already assigned for other uses, protected areas, current land use/cover of the different zones, and urban areas maps were incorporated into the GIS and subtracted by a mask. This resulted in the delimitation of "potential cultivation zoning", thus avoiding possible conflicts surrounding the use of land and making the agro-ecological zonation more efficient. There is a broad agro-ecological zone for cultivation of S. persica that extends from Northern Argentina to approximately 41° South latitude, under dry-subhumid to semiarid climates. Lands classified with different degrees of suitability in the potential cultivation zoning could be used for production of this species for energy purposes on lands that are either unsuitable for food production or currently assigned for other purposes. This paper represents pioneering work since there are no previous studies concerning the introduction of S. persica in Argentina.

Two-stage culture for producing berberine by cell suspension and shoot cultures of Berberis buxifolia Lam.

In vitro cultures of Berberis buxifolia were established using thidiazuron (4.5, 23 and 45 mM) or picloram (4 and 40 mM) as plant growth regulators for sustaining growth. For producing berberine, a two-stage culture was performed. In the first step, thidiazuron or picloram were used for biomass production followed by the production stage where benzylaminopurine (4.4 mM) was added as a plant growth regulator. Berberine yields (102 mg g(-1) DW) and in vitro shoot cultures (200 mg g(-1) DW) were significantly lower than those of whole plants in the field (416 mg g(-1) DW). The highest productivity (0.18 mg 1(-1) day(-1)) was attained using picloram (either 4 on 40 mM) in the first stage for producing biomass.

How polyamine synthesis inhibitors and cinnamic acid affect tropane alkaloid production.

Hairy roots of Brugmansia candida produce the tropane alkaloids scopolamine and hyoscyamine. In an attempt to divert the carbon flux from competing pathways and thus enhance productivity, the polyamine biosynthesis inhibitors cyclohexylamine (CHA) and methylglyoxal-bis-guanylhydrazone (MGBG) and the phenylalanine-ammonia-lyase inhibitor cinnamic acid were used. CHA decreased the specific productivity of both alkaloids but increased significantly the release of scopolamine (approx 500%) when it was added in the mid-exponential phase. However, when CHA was added for only 48 h during the exponential phase, the specific productivity of both alkaloids increased (approx 200%), favoring scopolamine. Treatment with MGBG was detrimental to growth but promoted release into the medium of both alkaloids. However, when it was added for 48 h during the exponential phase, MGBG increased the specific productivity (approx 200%) and release (250- 1800%) of both alkaloids. Cinnamic acid alone also favored release but not specific productivity. When a combination of CHA or MGBG with cinnamic acid was used, the results obtained were approximately the same as with each polyamine biosynthesis inhibitor alone, although to a lesser extent. Regarding root morphology, CHA inhibited growth of primary roots and ramification. However, it had a positive effect on elongation of lateral roots.

In vitro procuction of scopolamine and hyoscyamine: influence of different elicitors on hairy root cultures of Brugmansia candida

The tropane alkaloids scopolamine and hyoscyamine arestill extracted from plants that belong to several species of Solanaceae because their chemical syntesis is difficult and expensive. These anticholinergic agents are employed in medicine as antispasmodics, preoperative medication and for the treatment of motion sickness. In our laboratory, hairy roots of Brugmansia candida, a South American plant which both alkaloids, were obtained through transformation with Agrobacterium rhizogenes and cultured in vitro. To increase the productivity of the cultures, these were exposed to different elicitors: CaCl2, salicylic acid and autoclaved roots of B. candida. The effects on growth, alkaloid accumulation and release into the medium were evaluated. CaCl2 at 50.00 and 100.00 mM, increased the accumulation of scopolamine and hyoscyamine after 24 hours ( 30-60per cent), while after 48 hour levels of 50.00 mM decreased their accumulation ( 50per cent). No effect was observed on release of alkaloids into the medium. Salicylic acid, a compound involved in plant defense, at 0.01 and 1.00 mM increased accumulation of booth alkaloids (ranging from 30 to 170 per cent), particularly after 24 and 48 hours. There was also increase in the release of scopolamine and hyoscyamine into the medium. The homogenized roots had a positive effect on alkaloid accumulation in the roots throughout the experiment (ranging from 100 to 500 per cent). This was most noticeable for hyoscyamine, particulary after 24 and 72 hours of exposition. The results seen with homogenized roots are probably due to endogenous elicitors which are liberated in the subsequent steps of autoclaving and sonication.