Functional characterization of an acidic SK(3) dehydrin isolated from an Opuntia streptacantha cDNA library.

Cactus pears are succulent plants of the Cactaceae family adapted to extremely arid, hot and cold environments, making them excellent models for the study of molecular mechanisms underlying abiotic stress tolerance. Herein, we report a directional cDNA library from 12-month-old cladodes of Opuntia streptacantha plants subjected to abiotic stresses. A total of 442 clones were sequenced, representing 329 cactus pear unigenes, classified into eleven functional categories. The most abundant EST (unigen 33) was characterized under abiotic stress. This cDNA of 905 bp encodes a SK(3)-type acidic dehydrin of 248 amino acids. The OpsDHN1 gene contains an intron inserted within the sequence encoding the S-motif. qRT-PCR analysis shows that the OpsDHN1 transcript is specifically accumulated in response to cold stress, and induced by abscisic acid. Over-expression of the OpsDHN1 gene in Arabidopsis thaliana leads to enhanced tolerance to freezing treatment, suggesting that OpsDHN1 participates in freezing stress responsiveness. Generation of the first EST collection for the characterization of cactus pear genes constitutes a useful platform for the understanding of molecular mechanisms of stress tolerance in Opuntia and other CAM plants.

Genetic consequences of interglacial isolation in a steppe bird.

In response to climate changes that have occurred during Pleistocene glacial cycles, taxa associated to steppe vegetation might have followed a pattern of historical evolution in which isolation and fragmentation of populations occurred during the short interglacials and expansion events occurred during the long glacial periods, in contrast to the pattern described for temperate species. Here, we use molecular genetic data to evaluate this idea in a steppe bird with Palaearctic distribution, the little bustard (Tetrax tetrax). Overall, extremely low genetic diversity and differentiation was observed among eight little bustard populations distributed in Spain and France. Mismatch distribution analyses showed that most little bustard populations expanded during cooling periods previous to, and just after, the last interglacial period (127,000-111,000 years before present), when steppe habitats were widespread across Europe. Coalescent-based methods suggested that glacial expansions have resulted in substantial admixture in Western Europe due to the existence of different interglacial refugia. Our results are consistent with a model of evolution and genetic consequences of Pleistocene cycles with low between-population genetic differentiation as a result of short-term isolation periods during interglacials and long-term exchange during glacial periods.

Avoiding over-implementation of agri-environmental schemes for steppe bird conservation: a species-focused proposal based on expert criteria.

This study presents an assessment, resulting from consultation with experts in steppe-bird conservation (scientists, officers and conservationists) using the Delphi method, of a broad range of agri-environmental measures (AEMs) which have been applied in agricultural areas in Spain, with particular reference to four threatened steppe bird species. The measures which experts have valued most highly relate to the maintenance of fallow land, the prohibition of agrochemicals and the suspension of certain agricultural practices when the species are nesting. Other AEMs which have frequently been mentioned as beneficial for steppe birds, including the maintenance of straw-mulched fallows and the abandonment of farmland, were rejected by the experts. The assessment showed a high degree of consensus between experts, although differences between the four studied species were detected. Delphi assessment indicated that different birds need different AEMs. In addition, expert evaluation showed that different AEMs can cause the same effect on the target species, which could generate an over-implementation of measures. Finally, we evaluated the financial implementation of the AEMs selected by the Delphi using a Special Protection Area for birds (SPA) in the Madrid region as a case study. All the hypothetical scenarios used yielded assumable costs, oscillating between 1 and 2 times the current AEMs expenditure. In conclusion, in extensive agrarian systems with already high conservation merits, the implementation of AEMS could be improved using species-specific assessments, thus avoiding over-implementation and improving the fit between costs and benefits for conservation.