Soil 13C–15N dynamics in an N2-fixing clover system under long-term exposure to elevated atmospheric CO2

Reduced soil N availability under elevated CO₂ may limit the plant's capacity to increase photosynthesis and thus the potential for increased soil C input. Plant productivity and soil C input should be less constrained by available soil N in an N₂‐fixing system. We studied the effects of Trifolium repens (an N₂‐fixing legume) and Lolium perenne on soil N and C sequestration in response to 9 years of elevated CO₂ under FACE conditions. ¹⁵N‐labeled fertilizer was applied at a rate of 140 and 560 kg N ha^?1 yr^?1 and the CO₂ concentration was increased to 60 Pa pCO₂ using ¹³C‐depleted CO₂. The total soil C content was unaffected by elevated CO₂, species and rate of ¹⁵N fertilization. However, under elevated CO₂, the total amount of newly sequestered soil C was significantly higher under T. repens than under L. perenne. The fraction of fertilizer‐N (f_N) of the total soil N pool was significantly lower under T. repens than under L. perenne. The rate of N fertilization, but not elevated CO₂, had a significant effect on f_N values of the total soil N pool. The fractions of newly sequestered C (f_C) differed strongly among intra‐aggregate soil organic matter fractions, but were unaffected by plant species and the rate of N fertilization. Under elevated CO₂, the ratio of fertilizer‐N per unit of new C decreased under T. repens compared with L. perenne. The L. perenne system sequestered more ¹⁵N fertilizer than T. repens: 179 vs. 101 kg N ha^?1 for the low rate of N fertilization and 393 vs. 319 kg N ha^?1 for the high N‐fertilization rate. As the loss of fertilizer‐¹⁵N contributed to the ¹⁵N‐isotope dilution under T. repens, the input of fixed N into the soil could not be estimated. Although N₂ fixation was an important source of N in the T. repens system, there was no significant increase in total soil C compared with a non‐N₂‐fixing L. perenne system. This suggests that N₂ fixation and the availability of N are not the main factors controlling soil C sequestration in a T. repens system.     

Carbon isotope composition of N2-fixing and N-fertilized legumes along an elevational gradient

Dinitrogen-fixing legumes are frequently assumed to be less water-use efficient than plants utilizing soil mineral N, because of the high respiratory requirements for driving N₂ fixation. However, since respiration is assumed not to discriminate against ¹³C, any differences in water-use efficiency exclusively due to respiration should not be apparent in carbon isotope discrimination () values. Our objective was to determine if the source of N (N₂ fixation versus soil N) had any effect on of field-grown grain legumes grown at different elevations. Four legume species, Glycine max, Phaseolus lunatus, P. vulgaris, and Vigna unguiculata, were grown on five field sites spanning a 633 m elevational gradient on the island of Maui, Hawaii. The legumes were either inoculated with a mixture of three effective strains of rhizobia or fertilized weekly with urea at 100 kg N ha^-1 in an attempt to completely suppress symbiotic N₂-fixing activity. In 14 of 20 analyses of stover and 12 of 15 analyses of seed values were significantly higher (p=0.10) in the inoculated plants than the N-fertilized plants. Nitrogen concentrations were generally higher in the fertilized treatments than the inoculated treatments. The different values obtained depending on N-source may have implications in using as an indicator of water-use efficiency or yield potential of legumes.     

Immunochemical localization of a region of chaperonin-60 important for productive interaction with chaperonin-10.

An IgG1 monoclonal antibody (mAb 54G8) which binds to both Bordetella pertussis chaperonin-60 (cpn60) and Escherichia coli cpn60 (GroEL) was produced. mAb 54G8 as well as Fab fragments prepared from this antibody were found to abolish the ability of chaperonin-10 (cpn10, GroES) to inhibit the ATPase activity of both B. pertussis cpn60 and E. coli cpn60. Electron microscopy was used to localize the binding site of the monoclonal antibody on the B. pertussis cpn60 molecule. In the absence of the antibody, the B. pertussis molecule exhibited the tetradecameric structure typical of cpn60. Both end views (showing 7-fold symmetry of the face of the molecule) and side views were evident. When mAb 54G8 was bound, B. pertussis cpn60 molecules appeared to be cross-linked so that they formed long chains. Only side views of the molecules were seen in these long chains. When B. pertussis cpn60 complexed with Fab fragments of mAb 54G8 was examined, chains were no longer observed. Instead, side views of B. pertussis cpn60 were often seen with Fab fragments extending from the ends of the molecule. These data indicate that mAb 54G8 appears to bind at or near the end of the B. pertussis cpn60 molecule and that binding of mAb 54G8 at this location affects the ability of cpn10 to productively interact with cpn60, most likely either by sterically blocking the binding of cpn10, by affecting the conformation of cpn60 in such a way that it no longer binds cpn10, or by inhibiting proper transduction of the effects of cpn10 binding.     

New markers for the neurofibromatosis-2 region generated by microdissection of chromosome 22

To identify new DNA markers around the neurofibromatosis-2 gene on human chromosome 22, the critical region (22q12-q13.1) was microdissected and microcloned from GTG-banded metaphase chromosomes. Eighteen thousand recombinant clones were obtained. Twenty-seven of 55 clones tested (50%) detected single-copy DNA sequences. Nine of nine clones analyzed in detail were found to map to chromosome 22. Interestingly one clone (EAN04) is part of the leukemia inhibitory factor gene which has previously been mapped to 22q11.2-q13.1. Four clones (EAN01, EAN47, EAN57, and EAN68) detect DNA polymorphisms. These probes were used to compare constitutional and tumor genotypes of 41 patients with acoustic neurinoma. Loss of constitutional heterozygosity was identified in 17 of 31 informative cases (55%). From our data we conclude that the microdissection library is a valuable resource for physical and genetic mapping studies in neurofibromatosis-2.     

Familial translocation 22/Y and partial autosomal trisomy in a young girl

Report on a translocation t(22;Y)(q12;p 13) with conservation of the NOR in normal members from 2 generations of a family. The proposita has in addition a small autosomal duplication, probably (1)(q44-ter) which could explain her mental deficiency.     

Studies of the structure of the T4 bacteriophage tail sheath: I. The recovery of three-dimensional structural information from the extended sheath

The extended tail sheath of bacteriophage T4 has been used to study the transfer of information from an electron micrograph to the three-dimensional reconstruction obtained from it. Two methods have been developed to assess micrograph images of helical particles and their reconstructions. First, a filter has been designed which eliminates all structure in the image inconsistent with the symmetry and assumed radius of the helical particle. Individual micrographs can therefore be assessed with respect to their consistency with the assumed symmetry and radius, before reconstruction. Second, a map of the root-meansquare deviation of individual reconstructions from their average provides a quantitative measure of the consistency of the individual sets of tail data and allows the regions in the average reconstruction which are most sensitive to differences between the particles to be identified.The averaged reconstruction is used to examine the problems related to resolution and reproducibility of the structural information and to define the extent of the different components of the extended sheath.     

Partial trisomy 15q1

Summary A supernumerary extra chromosome of maternal origin, precisely described from QM- and C-banding patterns, was studied in a mentally defective boy with a severe convulsive disorder. This case is considered to represent a specific phenotype of trisomy 15q1. The suggestion that in cases of partial trisomy 15q different phenotypes are due to the second chromosome involved in interchange is supported by the observation of a tertiary trisomy in 2 sibs. It resulted from a balanced reciprocal translocation in the mother t(8q+15q-) and caused an unusual malformation syndrome (mental deficiency, cleft lip and palate, funnel chest, hypospadias).     

The protein-mediated transfer of phosphatidylcholine between membranes. The effect of membrane lipid composition and ionic composition of the medium.

The phosphatidylcholine exchange protein from bovine liver catalyzes the transfer of phosphatidylcholine between rat liver mitochondria and sonicated liposomes. The effect of changes in the liposomal lipid composition and ionic composition of the medium on the transfer have been determined. In addition, it has been determined how these changes affected the electrophoretic mobility i.e. the surface charge of the membrane particles involved. Transfer was inhibited by the incorporation of negatively charged phosphatidic acid, phosphatidylserine, phosphatidylglycerol and phosphatidylinositol into the phosphatidylcholine-containing vesicles; zwitterionic phosphatidyl-ethanolamine had much less of an inhibitory effect while positively charged stearylamine stimulated. The cation Mg2+ and, to a lesser extent, K+ overcame the inhibitory effect exerted by phosphatidic acid, in that concentration range where these ions neutralized the negative surface charge most effectively. Under conditions where Mg2+ and K+ affected the membrane surface charge relatively little inhibition was observed. In measuring the protein-mediated transfer between a monolayer and vesicles consisting of only phosphatidylcholine, cations inhibited the transfer in the order La3+ greater than Mg2+ larger than or equal to Ca2+ greater than K+ = Na+. Inhibition was not related to the ionic strength, and very likely reflects an interference of these cations with an electrostatic interaction between the exchange protein and the polar head group of phosphatidylcholine.