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.     

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.     

Inducible cell lysis system for the study of natural transformation and environmental fate of DNA released by cell death.

Two novel conditional broad-host-range cell lysis systems have been developed for the study of natural transformation in bacteria and the environmental fate of DNA released by cell death. Plasmid pDKL02 consists of lysis genes S, R, and Rz from bacteriophage lambda under the control of the Ptac promoter. The addition of inducer to Escherichia coli, Acinetobacter calcoaceticus, or Pseudomonas stutzeri containing plasmid pDKL02 resulted in cell lysis coincident with the release of high amounts of nucleic acids into the surrounding medium. The utility of this lysis system for the study of natural transformation with DNA released from lysed cells was assessed with differentially marked but otherwise isogenic donor-recipient pairs of P. stutzeri JM300 and A. calcoaceticus BD4. Transformation frequencies obtained with lysis-released DNA and DNA purified by conventional methods and assessed by the use of antibiotic resistance (P. stutzeri) or amino acid prototrophy (A. calcoaceticus) for markers were comparable. A second cell lysis plasmid, pDKL01, contains the lysis gene E from bacteriophage phi X174 and causes lysis of E. coli and P. stutzeri bacteria by activating cellular autolysins. Whereas DNA released from pDKL02-containing bacteria persists in the culture broth for days, that from induced pDKL01-containing bacteria is degraded immediately after release. The lysis system involving pDKL02 is thus useful for the study of both the fate of DNA released naturally into the environment by dead cells and gene transfer by natural transformation in the environment in that biochemically unmanipulated DNA containing defined sequences and coding for selective phenotypes can be released into a selected environment at a specific time point. This will allow kinetic measurements that will answer some of the current ecological questions about the fate and biological potential of environmental DNA to be made.     

DNA Isolation and GC Base Composition of Four Root-knot Nematode (Meloidogyne spp.) Genomes

Phenol extraction and cesium trifluoroacetate ultracentrifugation were compared for efficiency in the extraction of DNA from eggs and second-stage juveniles of four species of Meloidogyne. The second method proved to be more satisfactory in that it yielded larger amounts of DNA, shortened the extraction period, and reduced sample handling by eliminating phenol and ether extraction and RNAse treatment. It also made possible the extraction of DNA: from more than one sample at a time. The mean base compositions (% GC) of the total DNA of M. incognita, M. javanica, M. arenaria, and M. hapla, as determined by thermal denaturation tests, were quite similar, as they ranged only between 31 and 33%. Similarly, the thermal stability of the DNA of all four species covered a narrow range from 82.97 to 83.63 C.     

Influence of various factors on quantitative composition of leaf monoterpenes ofPicea abies (L.) Karst

Summary The extractable monoterpenes from needles of two groups of trees — 4-year-old clonal and 20-year-old wild trees — were studied with respect to the influence of individual constitution, needle age, whorl position, and position on branch. Leaf terpene amounts from clonal trees are significantly affected by age and position of the whorl, whereas position on the branch is of minor importance. Developing needles of clonal trees are most strongly affected by age and whorl position and they differ markedly from mature needles in quantitative terpene composition. Wild trees exhibit a very high variation from tree to tree, which obscures the influence of needle age and position. For this reason meaningful tree leaf terpene data will only be derived if large samples of needles of different ages are collected from distinct positions. When comparing different trees, needles should be selected that not only have the same state of development, but also originate from identical positions and have been subjected to the same light treatment.     

Glutamine and Glutamate Transport in Cyanophora paradoxa

The present investigation showed that isolated cyanelles from Cyanophora paradoxa selectively enriched glutamine from the external medium, whereas glutamate poorly penetrated into these organelles. Glutamine uptake proceeded in two phases, presumably involving a low and a high affinity system. The uptake of glutamine was significantly enhanced by 2-oxoglutarate and light. Inhibitor experiments indicated that glutamine and 2-oxoglutarate were converted to glutamate by a ferredoxin-dependent glutamate synthase (GOGAT) reaction inside the cyanelles, and the glutamate formed at best slowly left these organelles. Such results were obtained independently of each other by measuring either the ¹⁴C-glutamine uptake or the 2-oxoglutarate and glutamine-dependent O₂ evolution. Glutamine is suggested to be the N-compound which is supplied to the eukaryotic host. Glutamine could be exported jointly with 2-oxoglutarate, possibly employing a common carrier. Cyanelles have apparently evolved glutamine (and oxoglutarate) carrier(s) with properties not yet described for any other organism.     

The nature of arginine auxotrophy in cutaneous populations of staphylococci.

L-Arginine was required for growth by a high percentage of strains of Staphylococcus species that were niche-specific and/or host-specific, but was usually not required for growth by species showing a wide host range. Growth stimulation patterns with arginine intermediates indicated that most of the auxotrophic strains had blocks in an early step(s) in arginine biosynthesis. These strains were designated phenotypically as Arg(CHG) according to the Salmonella typhimurium classification scheme. Staphylococcus simulans strains appeared to be either ArgA or Arg I. The ArgI strains of S. simulans and S. capitis had moderate to high ornithine carbamoyltransferase (EC 2.1.3.3) activities and therefore could not be designated as argI mutants. ArgI strains in other species had no or very low ornithine carbamoyltransferase activities. All of the natural Staphylococcus auxotrophs tested grew in the presence of L-citrulline and had moderate to high argininosuccinase (EC 4.3.2.1) activities. Arginine auxotrophs of species with a wide host range were often capable of reverting to arginine-independent or complete prototrophic growth, whereas auxotrophs of species that tended to be niche-specific and/or host-specific were incapable of reversion to arginine-independence, even in the presence of various mutagens. A relationship between the nature of arginine auxotrophy and habitat is suggested.