Somaclonal variation and in vitro induced mutagenesis in grapevine

Somaclonal and in vitro mutagen-induced variability was studied in grapevine. Plants of Vitis vinifera cv. Podarok Magaracha were regenerated from leaf explants through somatic embryogenesis. Chromosome counts of root tips was used for screening of regenerated plants. Among 242 studied plants, six (2.5%) tetraploids (2n=4x=76) were identified; all others were diploid (2n=2x=38). Neither chimeral, nor aneuploid plants were observed. Gamma-irradiation (5-100 Gy) increased tetraploid plant formation frequency of primary (7%) and embryogenic calluses (7.6%) and some aneuploid plants were also found. Colchicine treatment was not effective for the production of tetraploid plants. Variability among regenerated plants was also found after field testing. This revised version was published online in June 2006 with corrections to the Cover Date.     

Plant species richness in continental southern Siberia: effects of pH and climate in the context of the species pool hypothesis

Aim Many high‐latitude floras contain more calcicole than calcifuge vascular plant species. The species pool hypothesis explains this pattern through an historical abundance of high‐pH soils in the Pleistocene and an associated opportunity for the evolutionary accumulation of calcicoles. To obtain insights into the history of calcicole/calcifuge patterns, we studied species richness–pH–climate relationships across a climatic gradient, which included cool and dry landscapes resembling the Pleistocene environments of northern Eurasia. Location Western Sayan Mountains, southern Siberia. Methods Vegetation and environmental variables were sampled at steppe, forest and tundra sites varying in climate and soil pH, which ranged from 3.7 to 8.6. Species richness was related to pH and other variables using linear models and regression trees. Results Species richness is higher in areas with warmer winters and at medium altitudes that are warmer than the mountains and wetter than the lowlands. In treeless vegetation, the species richness–pH relationship is unimodal. In tundra vegetation, which occurs on low‐pH soils, richness increases with pH, but it decreases in steppes, which have high‐pH soils. In forests, where soils are more acidic than in the open landscape, the species richness–pH relationship is monotonic positive. Most species occur on soils with a pH of 6–7. Main conclusions Soil pH in continental southern Siberia is strongly negatively correlated with precipitation, and species richness is determined by the opposite effects of these two variables. Species richness increases with pH until the soil is very dry. In dry soils, pH is high but species richness decreases due to drought stress. Thus, the species richness–pH relationship is unimodal in treeless vegetation. Trees do not grow on the driest soils, which results in a positive species richness–pH relationship in forests. If modern species richness resulted mainly from the species pool effects, it would suggest that historically common habitats had moderate precipitation and slightly acidic to neutral soils.     

Monoamine-containing neurons in the optic ganglia of crustaceans and insects

Summary With the fluorescence method of Falck and Hillarp, the presence and localization of monoaminergic neurons in the optic ganglia of several crustaceans and insects have been investigated. It was found that in both classes the monoaminergic terminals, when present, appeared (especially in the medullae externa and interna of the crustaceans and the medulla of the insects) in strata specific for each species. So far, the only monoamine (visualized by this technique) present in the crustacean optic ganglia is dopamine, whereas in the Insecta, the catecholamines dopamine and noradrenaline, and the indolamine, 5-hydroxytryptamine, are found in the optic lobe. But in the Insecta, different species show different content of these amines.This work was supported by grants 2760-3 and 2760-4 from the Swedish Natural Science Research Council (R.E.), by a fellowship from Deutsche Forschungsgemeinschaft, and a grant from the Swedish Medical Research Council B72-14X-712-D7B (N.K.). We are very grateful to the director of the Department of Histology, Faculty of Medicine, Lund, Professor Bengt Falck, who put all his facilities and knowledge at our disposal.     

Microbial diversity in acidic thermal pools in the Uzon Caldera,Kamchatka

Microbial communities of four acidic thermal pools in the Uzon Caldera, Kamchatka, Russia, were studied using amplification and pyrosequencing of 16S rRNA gene fragments. The sites differed in temperature and pH: 1805 (60 °C, pH 3.7), 1810 (90 °C, pH 4.1), 1818 (80 °C, pH 3.5), and 1807 (86 °C, pH 5.6). Archaea of the order Sulfolobales were present among the dominant groups in all four pools. Acidilobales dominated in pool 1818 but were a minor fraction at the higher temperature in pool 1810. Uncultivated Archaea of the Hot Thaumarchaeota-related clade were present in significant quantities in pools 1805 and 1807, but they were not abundant in pools 1810 and 1818, where high temperatures were combined with low pH. Nanoarchaeota were present in all pools, but were more abundant in pools 1810 and 1818. A similar abundance pattern was observed for Halobacteriales. Thermophilic Bacteria were less diverse and were mostly represented by aerobic hydrogen- and sulfur-oxidizers of the phylum Aquificae and sulfur-oxidising Proteobacteria of the genus Acidithiobacillus. Thus we showed that extremely acidic hot pools contain diverse microbial communities comprising different metabolic groups of prokaryotes, including putative lithoautotrophs using energy sources of volcanic origin, and various facultative and obligate heterotrophs.     

Temperature effects on fish production across a natural thermal gradient

Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss. Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlying mechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment in Iceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across a stream temperature gradient (4–25 °C). Brown trout are at the northern limit of their geographic distribution in this system, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmest streams. A five‐month mark‐recapture study revealed that population abundance, biomass, growth rate, and production of trout all increased with stream temperature. We identified two mechanisms that contributed to these responses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the food web and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the warmer streams. We found little evidence to support a third potential mechanism: that external subsidies would play a more important role in the diet of trout with increasing stream temperature. Resource availability was also amplified through the trophic levels with warming, as predicted by metabolic theory in nutrient‐replete systems. These results highlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledge of warming impacts on natural communities and ecosystem functioning.     

Effect of methylglyoxal modification on the structure and properties of human small heat shock protein HspB6 (Hsp20)

Human small heat shock protein HspB6 (Hsp20) was modified by metabolic α-dicarbonyl compound methylglyoxal (MGO). At low MGO/HspB6 molar ratio, Arg13, Arg14, Arg27, and Arg102 were the primary sites of MGO modification. At high MGO/HspB6 ratio, practically, all Arg and Lys residues of HspB6 were modified. Both mild and extensive MGO modification decreased susceptibility of HspB6 to trypsinolysis and prevented its heat-induced aggregation. Modification by MGO was accompanied by formation of small quantities of chemically crosslinked dimers and did not dramatically affect quaternary structure of HspB6. Mild modification by MGO did not affect whereas extensive modification decreased interaction of HspB6 with HspB1. Phosphorylation of HspB6 by cyclic adenosine monophosphate (cAMP)-dependent protein kinase was inhibited after mild modification and completely prevented after extensive modification by MGO. Chaperone-like activity of HspB6 measured with subfragment 1 of skeletal myosin was enhanced after MGO modifications. It is concluded that Arg residues located in the N-terminal domain of HspB6 are easily accessible to MGO modification and that even mild modification by MGO affects susceptibility to trypsinolysis, phosphorylation by cAMP-dependent protein kinase, and chaperone-like activity of HspB6.     

Specific Inter-residue Interactions as Determinants of Human Monoacylglycerol Lipase Catalytic Competency: A ROLE FOR GLOBAL CONFORMATIONAL CHANGES*

The serine hydrolase monoacylglycerol lipase (MGL) functions as the main metabolizing enzyme of 2-arachidonoyl glycerol, an endocannabinoid signaling lipid whose elevation through genetic or pharmacological MGL ablation exerts therapeutic effects in various preclinical disease models. To inform structure-based MGL inhibitor design, we report the direct NMR detection of a reversible equilibrium between active and inactive states of human MGL (hMGL) that is slow on the NMR time scale and can be modulated in a controlled manner by pH, temperature, and select point mutations. Kinetic measurements revealed that hMGL substrate turnover is rate-limited across this equilibrium. We identify a network of aromatic interactions and hydrogen bonds that regulates hMGL active-inactive state interconversion. The data highlight specific inter-residue interactions within hMGL modulating the enzymes function and implicate transitions between active (open) and inactive (closed) states of the hMGL lid domain in controlling substrate access to the enzymes active site.