Evolution of the relaxin-like peptide family

Background  

The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1, 2 and 3, and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, INSL6 remain uncharacterised. The evolution of this family has been contentious; high sequence variability is seen between closely related species, while distantly related species show high similarity; an invertebrate relaxin sequence has been reported, while a relaxin gene has not been found in the avian and ruminant lineages.     

Development and application of a selective PCR-denaturing gradient gel electrophoresis approach to detect a recently cultivated Bacillus group predominant in soil

The worldwide presence of a hitherto-nondescribed group of predominant soil microorganisms related to Bacillus benzoevorans was analyzed after development of two sets of selective primers targeting 16S rRNA genes in combination with denaturing gradient gel electrophoresis (DGGE). The high abundance and cultivability of at least some of these microorganisms makes them an appropriate subject for studies on their biogeographical dissemination and diversity. Since cultivability can vary significantly with the physiological state and even between closely related strains, we developed a culture-independent 16S rRNA gene-targeted DGGE fingerprinting protocol for the detection of these bacteria from soil samples. The composition of the B. benzoevorans relatives in the soil samples from The Netherlands, Bulgaria, Russia, Pakistan, and Portugal showed remarkable differences between the different countries. Differences in the DGGE profiles of these communities in archived soil samples from the Dutch Wieringermeer polder were observed over time during which a shift from anaerobic to aerobic and from saline to freshwater conditions occurred. To complement the molecular methods, we additionally cultivated B. benzoevorans-related strains from all of the soil samples. The highest number of B. benzoevorans relatives was found in the soils from the northern part of The Netherlands. The present study contributes to our knowledge of the diversity and abundance of this interesting group of microbes in soils throughout the world.     

Characterization of Rhizobium etli and other Rhizobium spp. that nodulate Phaseolus vulgaris L. in an Austrian soil

Phaseolus vulgaris L. (common bean) is nodulated by rhizobia present in the fields around the Seibersdorf laboratory despite the fact that common bean has not been grown for a long time. Using PCR analysis with repetitive primers, plasmid profiles, nifH profiles, PCR-RFLP analysis of the 16S rRNA gene and of the 16S rRNA-23S rRNA intergenic spacer and the nodulation phenotype, two well-differentiating groups could be distinguished. One group showed high similarity to Rhizobium sp. R602sp, isolated from common bean in France, while the other showed the same characteristics as R. etli . We detected little variation in the symbiotic regions but found higher diversity when using approaches targeting the whole genome. Many isolates obtained in this study might have diverged from a limited number of strains, therefore the Austrian isolates showed high saprophytic and nodulation competence in that particular soil.     

Seasonal changes in the response of winter wheat to elevated atmospheric CO2 concentration grown in Open-Top Chambers and field tracking enclosures

Winter wheat was grown at ambient and elevated (ambient plus 350 μL L^–1) CO₂ concentrations in open top chambers and in field-tracking sun-lit climatized enclosures (elevated is 718 μL L^–1). There was no significant effect of CO₂ concentration on sheath, leaf and root biomass and leaf area in the early spring (January to April). 24-h canopy CO₂ exchange rate (CCER) was not significantly affected either. However, elevated CO₂ concentration increased CCER at midday, decreased evapotranspiration rate and increased instantaneous water-use-efficiency during early spring. Leaf, sheath and root nitrogen concentration per unit dry weight decreased and nonstructural carbohydrate concentration increased under elevated CO₂, and N-uptake per unit ground area decreased significantly (– 22%) towards the end of this period. These results contrast with results from the final harvest, when grain yield and biomass were increased by 19% under elevated CO₂. N concentration per dry weight was reduced by 5%, but N-uptake per unit ground area was significantly higher (+ 11%) for the elevated CO₂ treatment. 24-h and midday-CCER increased significantly more in late spring (period of 21 April to 30 May) (respectively by + 40% and 53%) than in the early spring (respectively 5% and 19%) in response to elevated CO₂. Midday evapotranspiration rate was reduced less by elevated CO₂ in the late spring (– 13%) than in early spring (– 21%). The CO₂ response of midday and 24-h CCER decreased again (+ 27% and + 23% resp.) towards the end of the growing season. We conclude that the low response to CO₂ concentration during the early spring was associated with a growth-restriction, caused by low temperature and irradiance levels. The reduction of nitrogen concentration, the increase of nonstructural carbohydrate, and the lower evapotranspiration indicated that CO₂ did have an effect towards the end of early spring, but not on biomass accumulation. Regression analysis showed that both irradiance and temperature affected the response to CO₂.     

Ca2+, annexins, and GTP modulate exocytosis from maize root cap protoplasts

Protoplasts isolated from root cap cells of maize were shown to secrete fucose-rich polysaccharides and were used in a patch-clamp study to monitor changes in whole-cell capacitance. Ca2+ was required for exocytosis, which was measured as an increase in cell capacitance during intracellular dialysis with Ca2+ buffers via the patch pipette. Exocytosis was stimulated significantly by small increases above normal resting [Ca2+]. In the absence of Ca2+, protoplasts decreased in size. In situ hybridization showed significant expression of the maize annexin p35 in root cap cells, differ-entiating vascular tissue, and elongating cells. Dialysis of protoplasts with maize annexins stimulated exocytosis at physiological [Ca2+], and this could be blocked by dialysis with antibodies specific to maize annexins. Dialysis with milli-molar concentrations of GTP strongly inhibited exocytosis, causing protoplasts to decrease in size. GTPgammaS and GDPbetaS both caused only a slight inhibition of exocytosis at physiological Ca2+. Protoplasts were shown to internalize plasma membrane actively. The results are discussed in relation to the regulation of exocytosis in what is usually considered to be a constitutively secreting system; they provide direct evidence for a role of annexins in exocytosis in plant cells.     

Effects of climate change on productivity of cereals and legumes; model evaluation of observed year-to-year variability of the CO2 response

The effect of elevated [CO₂] on the productivity of spring wheat, winter wheat and faba bean was studied in experiments in climatized crop enclosures in the Wageningen Rhizolab in 1991–93. Simulation models for crop growth were used to explore possible causes for the observed differences in the CO₂ response. Measurements of the canopy gas exchange (CO₂ and water vapour) were made continuously from emergence until harvest. At an external [CO₂] of 700 μmol mol^?1 Maximum Canopy CO₂ Exchange Rate (CCERmax) at canopy closure was stimulated by 51% for spring wheat and by 71% for faba bean. At the end of the growing season, above ground biomass increase at 700 μmol mol^?1 was 58% (faba bean), 35% (spring wheat) and 19% (winter wheat) and the harvest index did not change. For model exploration, weather data sets for the period 1975-88 and 1991–93 were used, assuming adequate water supply and [CO₂] at 350 and 700 μmol mol^?1. For spring wheat the simulated responses (35–50%) were at the upper end of the experimental results. In agreement with experiments, simulations showed smaller responses for winter wheat and larger responses for faba bean. Further model explorations showed that this differential effect in the CO₂ response may not be primarily due to fundamental physiological differences between the crops, but may be at least partly due to differences in the daily air temperatures during comparable stages of growth of these crops. Simulations also showed that variations between years in CO₂ response can be largely explained by differences in weather conditions (especially temperature) between growing seasons.     

Growth increment ofAlnus glutinosa upon dual inoculation with effective and ineffectiveFrankia strains

Investigations on the ecological function of ineffectiveFrankia strains and their behaviour in competition with effectiveFrankia strains indicated an enhanced plant growth upon dual inoculation with increasing amounts of effective (i.e. N₂-fixing)Frankia strains and simultaneous inoculation with a constant amount of an ineffectiveFrankia strain. Enhanced plant growth was measured as increase in plant height and total dry weight at constant shoot/root ratio. The stimulating effect of the ineffective strain was independent of the plant clone and was obtained with bothAlnus glutinosa clones W I and B II, which were resistant and susceptable, respectively, to the ineffective strain. Stimulation was also independent of the nodulation conditions. Short-term studies (7 weeks) under axenic conditions and greenhouse experiments during 3 months showed comparable results, not only in plant growth but also in nodule formation. Increment in plant growth was not necessarily correlated to higher nodule formation with the effectiveFrankia strains.     

Creating Novel Structures in Food Materials: The Role of Well-Defined Shear Flow

Structure formation in food materials is influenced by the ingredient properties and processing conditions. Until now, small structural elements, such as fibrils and crystals, have been formed using self-assembly, while processing was applied to create relatively large structures. The effect of self-assembly under flow is rarely studied for food materials, but it is widely studied for non-food systems. The use of well-defined flow, often simple shear, turned out to be essential to study and control the structure formation process in foods as well. This observation encouraged us to develop a number of different shearing devices that allowed processing of biopolymer systems under simple shear flow. This paper reviews our main findings. In the case of protein fibrillization, the shear rate was found to control the growth rate as well as the properties of the fibrils formed. In the case of dough processing, simple shear flow made the product more process tolerant and induced gluten migration. The use of shear flow for dense caseinate dispersions led to hierarchically structured and fibrous material. Based on the presented results, we conclude that introducing simple shear flow in food structuring processes can lead to a much broader range of structures, thereby better utilizing the full potential of food ingredients.