Soil-geomorphic significance of land surface characteristics in an arid mountain range,Mojave Desert,USA

Mountains comprise an extensive and visually prominent portion of the landscape in the Mojave Desert, California. Landform surface properties influence the role these mountains have in geomorphic processes such as dust flux and surface hydrology across the region. The primary goal of this study was to describe and quantify land surface properties of arid-mountain landforms as a step toward unraveling the role these properties have in soil-geomorphic processes. As part of a larger soil-geomorphic study, four major landform types were identified within the southern Fry Mountains in the southwestern Mojave Desert on the basis of topography and landscape position: mountaintop, mountainflank, mountainflat (intra-range low-relief surface), and mountainbase. A suite of rock, vegetation, and morphometric land surface characteristic variables was measured at each of 65 locations across the study area, which included an associated piedmont and playa. Our findings show that despite the variation within types, landforms have distinct land surface properties that likely control soil-geomorphic processes. We hypothesize that surface expression influences a feedback process at this site where water transports sediment to low lying areas on the landscape and wind carries dust and soluble salts to the mountains where they are washed between rocks, incorporated into the soil, and retained as relatively long-term storage. Recent land-based video and satellite photographs of the dust cloud emanating from the Sierra Cucapá Mountains in response to the 7.2-magnitude earthquake near Mexicali, Mexico, support the hypothesis that these landforms are massive repositories of dust.     

Species-specific responses of woodland birds to stand-level habitat characteristics: The dual importance of forest structure and floristics

Several species of woodland birds have recently declined in Britain and there is a need to understand better how species are distributed across a wide spectrum of habitat types in order to develop appropriate conservation management strategies. To assess habitat associations of 28 woodland species, a large-scale study was carried out across Great Britain. A total of 2668 stands embedded in 825 woodland sites were surveyed. The number of species recorded in each stand and the occurrence of each species was examined in relation to the unique (or marginal) effects of gross structural characteristics of stands (growth stage and understorey structure), plant species composition (floristics) expressed in terms of dominant tree, shrub layer and field layer species and both sets of variables considered together whilst controlling for the spatial distribution of sites and site identity. The number of species recorded was independently related to growth stage, understorey structure, tree composition and field layer type. Eighteen species showed at least one significant relationship in models containing structure variables only. Thirteen species showed at least one significant relationship in models containing floristic variables only. In models containing both structure and floristic variables; 14 species showed at least one significant relationship with a structure variable, 9 species with at least one floristic variable and 8 species with both at least one structure and at least one floristic variable. Different bird species showed individualistic patterns of association with habitat variables. Results suggest that structure and floristics have complex and inter-related effects on bird distribution across woodland stands. Some of the apparent relationships with structure were a consequence of between-stand differences in floristics and vice versa whilst in two cases relationships with structure variables became apparent after controlling for the masking effects of floristic variables. Both vegetation structure and floristics appear to be important determinants of composition in bird assemblages in British woodland, though gross structural factors have previously received most emphasis. The existence of species-specific responses to habitat variation suggests that habitat heterogeneity, embracing structure and floristics, should be a key element in conservation planning within forests especially in the light of uncertainty about future regional species pools due to climate change. We discuss how responses of birds to habitat variation at the level of stands can form a basis for developing large-scale conservation strategies within managed forests.     

Universal endogenous gene controls for bisulphite conversion in analysis of plant DNA methylation

Background

Protein extraction is a frequent procedure in biological research. For preparation of plant cell extracts, plant materials usually have to be ground and homogenized to physically break the robust cell wall, but this step is laborious and time-consuming when a large number of samples are handled at once.

Results

We developed a chemical method for lysing Arabidopsis cells without grinding. In this method, plants are boiled for just 10 minutes in a solution containing a Ca²⁺ chelator and detergent. Cell extracts prepared by this method were suitable for SDS-PAGE and immunoblot analysis. This method was also applicable to genomic DNA extraction for PCR analysis. Our method was applied to many other plant species, and worked well for some of them.

Conclusions

Our method is rapid and economical, and allows many samples to be prepared simultaneously for protein analysis. Our method is useful not only for Arabidopsis research but also research on certain other species.     

High Resolution Melt (HRM) analysis is an efficient tool to genotype EMS mutants in complex crop genomes

Background

Targeted Induced Loci Lesions IN Genomes (TILLING) is increasingly being used to generate and identify mutations in target genes of crop genomes. TILLING populations of several thousand lines have been generated in a number of crop species including Brassica rapa. Genetic analysis of mutants identified by TILLING requires an efficient, high-throughput and cost effective genotyping method to track the mutations through numerous generations. High resolution melt (HRM) analysis has been used in a number of systems to identify single nucleotide polymorphisms (SNPs) and insertion/deletions (IN/DELs) enabling the genotyping of different types of samples. HRM is ideally suited to high-throughput genotyping of multiple TILLING mutants in complex crop genomes. To date it has been used to identify mutants and genotype single mutations. The aim of this study was to determine if HRM can facilitate downstream analysis of multiple mutant lines identified by TILLING in order to characterise allelic series of EMS induced mutations in target genes across a number of generations in complex crop genomes.

Results

We demonstrate that HRM can be used to genotype allelic series of mutations in two genes, BraA.CAX1a and BraA.MET1.a in Brassica rapa. We analysed 12 mutations in BraA.CAX1.a and five in BraA.MET1.a over two generations including a back-cross to the wild-type. Using a commercially available HRM kit and the Lightscanner? system we were able to detect mutations in heterozygous and homozygous states for both genes.

Conclusions

Using HRM genotyping on TILLING derived mutants, it is possible to generate an allelic series of mutations within multiple target genes rapidly. Lines suitable for phenotypic analysis can be isolated approximately 8-9 months (3 generations) from receiving M₃ seed of Brassica rapa from the RevGenUK TILLING service.     

F2 screening for resistance to pyramided Bacillus thuringiensis maize in Louisiana and Mississippi populations of Diatraea saccharalis (Lepidoptera: Crambidae)

BACKGROUND: In the mid‐southern region of the United States, sugarcane borer, Diatraea saccharalis (F.), is a major target pest of transgenic maize expressing Bacillus thuringiensis (Bt) proteins. Novel transgenic maize technologies containing two or more pyramided Bt genes for controlling lepidopteran pests have recently become commercially available. Insect resistance management (IRM) is an important issue in the sustainable use of Bt crop technologies. The objective of this study was to determine the frequency of resistance alleles in field populations of D. saccharalis to the new pyramided Bt maize technologies. RESULTS: A total of 382 F₂ family lines derived from 735 feral larvae/pupae of D. saccharalis collected from six locations in Louisiana and Mississippi during 2008 and 2009 were screened for resistance to three new Bt maize technologies: MON 89034, Genuity? VT Triple Pro? and SmartStax?. None of the 382 F₂ isoline families survived on the Bt maize leaf tissue for ≥ 12 days in the F₂ screen. The joint frequency for two‐ or three‐gene resistance models with 95% probability in these populations was estimated to be < 0.0063 to MON 89034 and < 0.003 to VT Triple Pro? and SmartStax?. CONCLUSION: These results suggest that the resistance allele frequency in D. saccharalis to the three pyramided Bt maize technologies is low in the mid‐southern region of the United States, which should meet the rare resistance assumption of the currently used IRM strategy for Bt maize. Copyright © 2011 Society of Chemical Industry     

Perturbation of nutrient source–sink relationships by post‐anthesis stresses results in differential accumulation of nutrients in wheat grain

Mineral nutrients in grains act as a source of nutrients in human diets, in which deficiencies of key minerals including calcium, magnesium, copper, iron, and zinc have prompted efforts to increase their concentrations in the edible portions of staple grain crops. Wheat (Triticum aestivum L.) crops in many regions often suffer abiotic stresses such as drought, extreme heat or frost during grain filling, which affect mineral source–sink relationships. We hypothesized that these stresses would have nutrient‐specific impacts on grain nutrient concentrations due to differences among nutrients in phloem mobility, post‐anthesis uptake and grain loading patterns. Nutrient loading patterns into wheat grains were investigated in two wheat cultivars in the field by sequentially harvesting tagged ears and analyzing tissues for key nutrients. In addition, the impact of perturbed source–sink relations during grain filling on nutrient loading was investigated by inducing post‐anthesis drought /floret abortion in a glasshouse study. Over 90% of Ca and around 70% of Na, K, and Mg accumulated in both wheat cultivars in the field during the first 14 d of grain development. The concentrations of micronutrients (Mn, Fe, Cu and Zn), Mg and P in grains generally increased when florets were aborted, and were unchanged under drought stress, while concentrations of Ca and K were highest under drought stress and lowest under the 66% floret abortion treatment. The observed changes in grain nutrient concentrations from post‐anthesis drought/floret abortion could not be fully explained by nutrient‐specific differences in phloem mobility, post‐anthesis uptake and grain loading patterns. This study will inform future research to define the precise roles of individual nutrients within developing grains and to fully understand the observed variations in grain nutrient concentrations due to source/sink modifications.     

One-third of reef-building corals face elevated extinction risk from climate change and local impacts

The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures.