Translocation of 13N and 11C between Nodulated Roots and Leaves in Alfalfa Seedlings

The positron-emitting isotopes of nitrogen and carbon, ¹³N and¹¹C, in the form of ¹³N₂, , and ¹¹CO₂ have been used successively on the same plant to investigatetracer movement between root nodules and shoots in young alfalfaseedlings. The mass flow profiles of ¹¹C photosynthate appearsimilar in shape in both stem and root but differ in speed;the speed of movement is significantly slower in roots thanin shoots (0?3 cm min^–1 compared with 0?5 cm min^–1)apparently in the phloem. Root nodules are sinks for the ¹¹Clabel. ¹³N fixation occurred in <3 min in root nodules andwas followed by export of ¹³N compounds in less than 30 minafter presentation in strong light. Fixation seems to be dependenton photosynthate supply. ¹³N export from the root nodules washighly irregular in profile and not a simple steady-state massflow. The speed of movement of ¹³N fixation compounds, and , suggests transport in the xylem, at rates of 6–12 cm min^–1 acropetally bothin root and shoot. Key words: Alfalfa seedlings, Translocation, Roots, Leaves, Carbon isotope ¹¹C, Nitrogen isotope ¹³N     

The Movement of Calcium in Woody Stems

The movement of radioactive calcium through excised pieces of1-year-old apple stem was observed to be much slower than thatof phosphate supplied at the same time. Chelation and the presenceof competing cations increased the speed at which calcium movedthrough the stem pieces. Movement of calcium in the xylem appearsto be normally by exchange rather than by mass flow. Some calciumentering the xylem appears to become more firmly bound and somemay move to phloem tissues.     

Crystal and Molecular Structure of (+)-Carba-Thymidine,C11 H10 N2 O6

Abstract

The molecular structure of (+)-carba-thymidine possessing notable anti-HSV activity has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group P2 with unit cell dimensions a = 4.810(2), b = 11.560(1)¹, c = 10.014(1) A, β = 92.34(2)°, Z = 2. The structure was solved by direct methods and refined by least squares to a final R = 0.038 for 1027 reflections (I < 36(I)). The torsion angle x around the glycosidic N1-C1′ bond agrees with that of thymidine (37.5°vs 39.1°) whereas the C3′-exo pucker of the five-membered ring is shifted to an even less common C1′-eao form.     

Fine Roots vs. Needles: A Comparison of 13C and 15N Dynamics in a Ponderosa Pine Forest Soil

Plant allocation patterns may affect soil C and N storage due to differences in litter quality and the depth of plant C and N inputs into the soil. We studied the dynamics of dual-labeled (¹³C/¹⁵N) Pinus ponderosa needles and fine roots placed at two soil depths (O and A horizon) in a temperate conifer forest soil during 2 y. Input of C as fine roots resulted in much more C retained in soil (70.5 ± 2.2% of applied) compared with needle C (42.9 ± 1.3% of applied) after 1.5 y. Needles showed faster mass loss, rates of soil ¹³CO₂ efflux, and more ¹⁵N immobilized into microbial biomass than did fine roots. The larger proportion of labile C compounds initially present in needles (17% more needle C was water soluble than in fine roots) likely contributed to its shorter C residence time and greater degree of transformation in the soil. A double exponential decay function best described the rate of ¹³C loss, with a smaller initial pulse of C loss from fine roots (S₁k₁) and a slower decay rate of the recalcitrant C pool for fine roots (0.03 y⁻¹) compared with (0.19 y⁻¹) for needles. Soil ¹³C respiration, representing heterotrophic respiration of litter C, was much more seasonal from the O horizon than from the A. However, offsetting seasonal patterns in ¹³C dynamics in the O horizon resulted in no net effect of soil depth on total ¹³C retention in the soil after 1.5 y for either litter. Almost 90% of applied litter N was retained in the soil after 1.5 y, independent of litter quality or soil depth. Very small amounts of ¹³C or ¹⁵N (<3% of applied) moved to the horizon above or below the placement depth (i.e., O to A or A to O). Our results suggest that plant allocation belowground to fine roots results in more C retained and less N mineralized compared with allocation aboveground to needles, primarily due to litter quality differences.     

C 11/D 13-translocation in four generations

Summary In a pedigree with familial C 11/D 13-translocation the chromosomes of 18 persons in 4 generations were analyzed. 8 of them had a normal karyotype, in 8 cases a balanced translocation was found. Totally 7 children with different multiple malformations were observed, 5 of whom had already died at the time of investigation. The other 2 showed an unbalanced translocation C 11/D 13 with partial trisomy for the long arm of chromosome C 11. These children showed the same syndrome (mental retardation, low birth weight, cutis laxa, hypertelorism, broad flat nose, micrognathia with retracted lower lip, heart malformation, ridge dysplasia of dermatoglyphics).One woman of the third generation with a balanced translocation C 11/D 13 additionally showed a triplo-X constitution. Among 10 pregnancies this woman had 5 abortions and 5 children, 2 of them with multiple malformations.

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Zusammenfassung In einem Stammbaum mit familiärer C 11/D 13-translokation wurden die Chromosomen von 18 Personen in 4 Generationen untersucht. Bei 8 Personen fand sich ein normaler Karyotyp, in 8 Fällen war eine balancierte Translokation vorhanden. Insgesamt wurden 7 Kinder mit verschiedenen Mißbildungen registriert, von denen 5 zur Zeit der Untersuchung bereits verstorben waren. Bei den beiden anderen wurde eine unbalancierte C 11/D 13-Translokation mit partieller trisomie für den langen Arm des Chromosoms C 11 gefunden. Diese Kinder wiesen das gleiche Mißbildungssyndrom mit geistiger Retardierung, geringem Geburtsgewicht, Cutis laxa, Hypertelorismus, breiter flacher Nase, Mikrognathie mit eingezogener Unterlippe, Herzfehler und Hautleistendysplasien auf.Eine Frau der dritten Generation wies neben der balancierten C 11/D 13-Translokation ein Triplo-X auf. Von 10 Schwangerschaften endeten bei dieser Frau 5 mit einem Abort, 2 Kinder starben an multiplen Mißbildungen, und lediglich 3 Kinder waren gesund.

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With Technical Assistance of Ch. Hägele     

C and N allocation in soil under ryegrass and alfalfa estimated by 13C and 15N labelling

Background and Aims

Below-ground translocated carbon (C) released as rhizodeposits is an important driver for microbial mobilization of nitrogen (N) for plants. We investigated how a limited substrate supply due to reduced photoassimilation alters the allocation of recently assimilated C in plant and soil pools under legume and non-legume species.

Methods

A non-legume (Lolium perenne) and a legume (Medicago sativa) were labelled with ¹⁵N before the plants were clipped or shaded, and labelled twice with ¹³CO₂ thereafter. Ten days after clipping and shading, the ¹⁵N and ¹³C in shoots, roots, soil, dissolved organic nitrogen (DON) and carbon (DOC) and in microbial biomass, as well as the ¹³C in soil CO₂ were analyzed.

Results

After clipping, about 50 % more ¹³C was allocated to regrowing shoots, resulting in a lower translocation to roots compared to the unclipped control. Clipping also reduced the total soil CO₂ efflux under both species and the ¹³C recovery of soil CO₂ under L. perenne. The ¹⁵N recovery increased in the shoots of M. sativa after clipping, because storage compounds were remobilized from the roots and/or the N uptake from the soil increased. After shading, the assimilated ¹³C was preferentially retained in the shoots of both species. This caused a decreased ¹³C recovery in the roots of M. sativa. Similarly, the total soil CO₂ efflux under M. sativa decreased more than 50 % after shading. The ¹⁵N recovery in plant and soil pools showed that shading has no effect on the N uptake and N remobilization for L. perenne, but, the ¹⁵N recovery increased in the shoot of M. sativa.

Conclusions

The experiment showed that the dominating effect on C and N allocation after clipping is the need of C and N for shoot regrowth, whereas the dominating effect after shading is the reduced substrate supply for growth and respiration. Only slight differences could be observed between L. perenne and M. sativa in the C and N distribution after clipping or shading.     

Tangential Movement of 14C-labelled Assimilates in Stems of Willow

It was shown that, when ¹⁴CO₂, was fed to a single leafy shootof a rooted willow cutting, activity appeared within 12 hrs.in honeydew collected from a colony of the aphid Tuberolachnussalignus (Gmelin), feeding on the opposite side of the stem20 cm. below the base of the leafy shoot. This was shown tobe due to a tangential movement of labelled materials throughthe bark. This tangential movement was found only in cuttings with limitedroot growth. Where an active root sink was present, extensivetangential movement was absent. Using two aphid colonies on either side of the stem, determinationsof the speed of tangential movement have been made. The highestvalue obtained was 10.6 mm./hr.     

Letter to the Editor: 1H, 15N and 13C resonance assignments of rabbit apo-S100A11

S100 proteins belong to the EF-hand family of calcium binding proteins. Upon calcium binding, these proteins undergo a conformational change to expose a hydrophobic region necessary for target protein interaction. One member of the S100 protein family is S100A11, first isolated from chicken gizzard and termed calgizzarin. It was later isolated from other organisms and tissues including human placenta, pig heart and rabbit lung. The physiological target of S100A11 is thought to be annexin I, a phospholipid-binding protein involved in EGF receptor sorting. This work reports the ¹H, ¹⁵N and ¹³C resonance assignments of rabbit apo-S100A11 determined using ¹⁵N, ¹³C-labelled protein and multidimensional NMR spectroscopy.     

Cross-peptide bond 13C--15N coupling constants by 13C and J cross-polarization 15N NMR

Comparative 13C--15N coupling constants are reported for the linear dipeptide tBoc-L-[U-13C]Ala-[15N]GlyOMe and the corresponding cyclic diketopiperazine, both in dimethylsulfoxide (DMSO) and, upon removal of the tBoc group, in water solutions. Spectra were obtained by 13C NMR and by the first application of J cross-polarization (JCP) 15N NMR, which greatly reduces the time required to accumulate 15N NMR spectra. In DMSO there was evidence for the formation of complexed species which were not present in water. The values obtained for the cross-peptide bond coupling constant 2J13C alpha--15N were consistently less (by 2.2 Hz in DMSO, 4.3 Hz in water) for the cyclic than for the linear peptide, which may be related to the cross-peptide bond conformation. The 15N resonance for the cyclic peptide was shifted only 2 ppm downfield from the linear peptide chemical shift value in both solvents.     

病毒在植物体内的运转

病毒能否引致植物发病,取决于病毒侵入植物后能否运转到植物的其它部分.一般认为病毒是通过由生物介体或机械磨擦造成的机械损伤而侵入植物细胞的.从初始侵染的细胞开始,大多数病毒在植物体内有两种运转方式:在薄壁细胞间进行的缓慢的短距离运转;在输导组织间进行的快速的长距离运转.80年代中期认识到病毒的体内运转需要其基因产物(运动蛋白,movement protem,MP)的参与,证实了烟草花叶病毒(TMV)的30kD蛋白即为TMV的MP[1,2].之后有关病毒MP及对病毒如何在植物体内进行运转的研究取得很大的进展.有关这方面的综述文章有Hull R、Atabekov等、Lucas等和Carrington等[3-6]的.本文主要综述近五年来的研究进展,但为了其完整性,也包含了一些上述综述的主要有关内容.     

Translocation Profiles of [11C] and [13N]-Labelled Metabolites after Assimilation of 11CO2 and [13N]-Labelled Ammonia Gas by Leaves of Helianthus annuus L. and Lupinus albus L.

Tracer amounts of atmospheric [¹³N]-Iabelled ammonia gas, wereabsorbed by leaves of Lupinus albus and Helianthus annuus inboth the light and the dark. Exogenous [¹³N]-ammonia was onlyabsorbed in the dark when the feeding occurred shortly aftera period of illumination and the tissue was not depleted ofits carbohydrate reserves (e.g. starch). Incorporation of the[¹³N]-ammonia appeared to occur via the leaf glutamine synthetase/glutamatesynthase (GS/GOGAT) cycle since 2.0 mol m^–3 MSX, an inhibitorof the GS reduced uptake in both the light and dark. Photosyntheticincorporation of ¹¹CO₂ was not affected by this treatment Therate of movement of [¹³N]-assimilates in the petiole of attachedleaves of Helianthus and Lupinus was similar to that of the¹¹Cl-photo assimilates. Export of both [¹³N] and [¹¹C]-Iabelledassimilates from the leaf and movement in the petiole in boththe light and the dark was inhibited by source leaf anoxia (i.e.nitrogen gas). Translocation was re-established at the samerate when the feed leaf was exposed to gas containing more than2% O₂ which permitted dark respiration to proceed. After aninitial feeding of either ¹¹CO₂ or [¹³N]-ammonia at ambient(21%) O₂ exposure of the source leaf to 2% O2, or 50% O² didnot alter the rates of translocation, indicating that changesin photosynthetic activity in the source leaf due to photorespiratoryactivity need not markedly alter, at least during the shortperiod, the loading and translocation of either [¹¹C ] or [¹³N]-labelledleaf products. Key words: Translocation, CO₂, NH₃, Leaves, Helianthus annuus, Lupinus albus     

Fine mapping of the diabetes-susceptibility locus, IDDM4, on chromosome 11q13.

Genomewide linkage studies of type 1 diabetes (or insulin-dependent diabetes mellitus [IDDM]) indicate that several unlinked susceptibility loci can explain the clustering of the disease in families. One such locus has been mapped to chromosome 11q13 (IDDM4). In the present report we have analyzed 707 affected sib pairs, obtaining a peak multipoint maximum LOD score (MLS) of 2.7 (lambda(s)=1.09) with linkage (MLS>=0.7) extending over a 15-cM region. The problem is, therefore, to fine map the locus to permit structural analysis of positional candidate genes. In a two-stage approach, we first scanned the 15-cM linked region for increased or decreased transmission, from heterozygous parents to affected siblings in 340 families, of the three most common alleles of each of 12 microsatellite loci. One of the 36 alleles showed decreased transmission (50% expected, 45.1% observed [P=.02, corrected P=.72]) at marker D11S1917. Analysis of an additional 1,702 families provided further support for negative transmission (48%) of D11S1917 allele 3 to affected offspring and positive transmission (55%) to unaffected siblings (test of heterogeneity P=3x10-4, corrected P=. 01]). A second polymorphic marker, H0570polyA, was isolated from a cosmid clone containing D11S1917, and genotyping of 2,042 families revealed strong linkage disequilibrium between the two markers (15 kb apart), with a specific haplotype, D11S1917*03-H0570polyA*02, showing decreased transmission (46.4%) to affected offspring and increased transmission (56.6%) to unaffected siblings (test of heterogeneity P=1.5x10-6, corrected P=4.3x10-4). These results not only provide sufficient justification for analysis of the gene content of the D11S1917 region for positional candidates but also show that, in the mapping of genes for common multifactorial diseases, analysis of both affected and unaffected siblings is of value and that both predisposing and nonpredisposing alleles should be anticipated.     

Leaf-like Structure in the Photosynthetic, Succulent Stems of Cacti

This research examined the hypothesis that as cacti evolve tothe leafless condition, the stem epidermis and cortex becomemore leaflike and more compatible with a photosynthetic role.All cacti in the relict genus Pereskia have non-succulent stemsand broad, thin leaves. All members of the derived subfamilyCactoideae are ‘leafless’, having an expanded cortexthat is the plant's only photosynthetic tissue. In Pereskia,leaves have a high stomatal density (mean: 50.7 stomata mm^–2in the lower epidermis, 38.1 mm^–2 in the upper epidermis),but stems have low stomatal densities (mean: 11.3 mm ₂, threeof the species have none). Stems of Cactoideae have a high stomataldensity (mean: 31.1 mm^–2, all species have stomata). Theouter cortex cells of stems of Cactoideae occur in columns,forming a palisade cortex similar to a leaf palisade parenchyma.In this palisade cortex, the fraction of tissue volume availablefor gas diffusion has a mean volume of 12.9%, which is identicalto that of Pereskia leaf palisade parenchyma. Pereskia stemcortex is much less aerenchymatous (mean: 5.3% of cortex volume).Cactoideae palisade cortex has a high internal surface density(0.0207 cm₂ cm^–2 which is higher than in Pereskia stemcortex (0.0150 cm₂ cm^–3) but not as high as Pereskia leafpalisade parenchyma (0.0396 cm₂ cm^–3). Pereskia stem cortexhas no cortical bundles, but Cactoideae cortexes have extensivenetworks of collateral vascular bundles that resemble leaf veins. Cactaceae, cactus, intercellular space, stomatal density, internal surface/volume, evolution     

1H, 13C and 15N resonance assignments of the Calmodulin-Munc13-1 peptide complex

Ca²⁺-Calmodulin binding to the variable N-terminal region of the diacylglycerol/phorbol ester-binding UNC13/Munc13 family of proteins modulates the short-term synaptic plasticity characteristics in neurons. Here, we report the sequential backbone and side chain resonance assignment of the Ca²⁺-Calmodulin/Munc13-1^458–492 peptide complex at pH 6.8 and 35°C (BMRB No. 15470).     

Biosynthetic uniform 13C,15N-labelling of zervamicin IIB. Complete 13C and 15N NMR assignment.

Zervamicin IIB is a member of the alpha-aminoisobutyric acid containing peptaibol antibiotics. A new procedure for the biosynthetic preparation of the uniformly 13C- and 15N-enriched peptaibol is described This compound was isolated from the biomass of the fungus-producer Emericellopsis salmosynnemata strain 336 IMI 58330 obtained upon cultivation in the totally 13C, 15N-labelled complete medium. To prepare such a medium the autolysed biomass and the exopolysaccharides of the obligate methylotrophic bacterium Methylobacillus flagellatus KT were used. This microorganism was grown in totally 13C, 15N-labelled minimal medium containing 13C-methanol and 15N-ammonium chloride as the only carbon and nitrogen sources. Preliminary NMR spectroscopic analysis indicated a high extent of isotope incorporation (> 90%) and led to the complete 13C- and 15N-NMR assignment including the stereospecific assignment of Aib residues methyl groups. The observed pattern of the structurally important secondary chemical shifts of 1H(alpha), 13C=O and 13C(alpha) agrees well with the previously determined structure of zervamicin IIB in methanol solution.     

Amine inversion in proteins. A 13C-NMR study of proton exchange and nitrogen inversion rates in N epsilon,N epsilon,N alpha,N alpha-[13C]tetramethyllysine,N epsilon,N epsilon,N alpha,N alpha-[13C]tetramethyllysine methyl ester, and reductively methylated concanavalin A

Exchange rates were calculated as a function of pH from line widths of methylamine resonances in 13C-NMR spectra of N epsilon,N epsilon,N alpha,N alpha-[13C]tetramethyllysine (TML) and N epsilon,N epsilon,N alpha,N alpha-tetramethyllysine methyl ester (TMLME). The pH dependence of the dimethyl alpha-amine exchange rate could be adequately described by assuming base-catalyzed chemical exchange between two diastereotopic methyl populations related by nitrogen inversion. Deprotonation of the alpha-amine was assumed to occur by proton transfer to (1) OH-, (2) water, (3) a deprotonated amine or (4) RCO2-. Microscopic rate constants characterizing each of these transfer processes (k1, k2, k3 and k4, respectively) were determined by fitting the rates calculated from line width analysis to a steady-state kinetic model. Using this procedure it was determined that for both TML and TMLME k2 approximately equal to 1-10 M-1 s-1, k3 approximately equal to 10(6) M-1 s-1 and ki, the rate constant for nitrogen inversion was about 10(8)-10(9) s-1. Upper limits of 10(12) and 10(3) M-1 s-1 could be determined for k1 and k4, respectively. A similar kinetic analysis was used to explain pH-dependent line-broadening effects observed for the N-terminal dimethylalanyl resonance in 13C-NMR spectra of concanavalin A, reductively methylated using 90% [13C]formaldehyde. From exchange data below pH 4 it could be determined that amine inversion was limited by the proton transfer rate to the solvent, with a rate constant estimated at 20 M-1 s-1. Above pH 4, exchange was limited by proton transfer to other titrating groups in the protein structure. Based upon their proximity, the carboxylate side chains of Asp-2 and Asp-218 appear to be likely candidates. The apparent first-order microscopic rate constant characterizing proton transfer to these groups was estimated to be about 1 X 10(4) s-1. Rate constants characterizing nitrogen inversion (ki), proton transfer to OH- (k1) and proton transfer to the solvent (k2) were estimated to be of the same order of magnitude as those determined for the model compounds. On the basis of our results, it is proposed that chemical exchange processes associated with base-catalyzed nitrogen inversion may contribute to 15N or 13C spin-lattice relaxation times in reductively methylated peptides or proteins.