Molecular biology of glycinergic neurotransmission

Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem of vertebrates. Glycine is accumulated into synaptic vesicles by a proton-coupled transport system and released to the synaptic cleft after depolarization of the presynaptic terminal. The inhibitory action of glycine is mediated by pentameric glycine receptors (GlyR) that belong to the ligand-gated ion channel superfamily. The synaptic action of glycine is terminated by two sodium- and chloride-coupled transporters, GLYT1 and GLYT2, located in the glial plasma membrane and in the presynaptic terminals, respectively. Dysfunction of inhibitory glycinergic neurotransmission is associated with several forms of inherited mammalian myoclonus. In addition, glycine could participate in excitatory neurotransmission by modulating the activity of the NMDA subtype of glutamate receptor. In this article, we discuss recent progress in our understanding of the molecular mechanisms that underlie the physiology and pathology of glycinergic neurotransmission.     

植物激素在大豆生殖器官脱落过程中的变化(英)

研究了大田生长条件下,大豆品种──早12花及幼荚脱落过程中植物激素变化。结果表明,自盛花期始,位于大豆第8～12节位的花序,其上、中、下三个部分花荚的脱落率逐渐升高,至最后一次取样时,三部分花荚的脱落率分别为77．4％、54．7％和18．3％,说明同一花序的基部花荚不易脱落。由内源细胞分裂素（iPA,ZRs,DHZRs）的分析发现,基部幼荚在生长前期,其内源iPA、ZRs、DHZRs均出现一个含量高峰,总CTK含量明显高于中、下部,而在后期脱落酸含量则明显较低;后期基部幼荚的生长速率及干物质积累量均高于中、上部。可见,植物激素参与调控了大豆生殖器官的脱落过程。     

一种自动化的植物细胞壁伸展性能测定仪及其应用

应用实验室常用仪器和电子部件,包括直流稳压电源、等臂双盘天平、记录仪、恒流泵、程控仪、线性可变差动变压器（LVDT）、电磁间等,改装和配置成的植物细胞壁伸展性能测定仪,具有操作简便、测量准确和灵敏度高等优点;对大豆幼苗下胚轴生长区细胞壁的内源伸展活性和重组伸展活性的实测结果与文献报告相符,表明该仪器是一种较为理想的准确测定植物细胞壁伸展性能的自动化仪器。     

Nitrate and ammonium influxes in soybean (Glycine max) roots: direct comparison of 13N and 15N tracing

We compared influxes and internal transport in soybean plants (Glycine max cv. Kingsoy) of labelled N from external solutions where either ammonium or nitrate was labelled with the stable isotope¹⁵N and the radioactive isotope¹³N. The objective was to see whether mass spectrometric determinations of tissue ¹⁵N content were sufficiently sensitive to measure influxes accurately over short time periods. Our findings were as follows. (1) There was a close quantitative correspondence between estimates of N influx of individual plants using ¹⁵N or ¹³N measurements with either NO_3/^? or NH₄⁺ at 4 or 2 mol^?3, respectively in the external solution. (2) Transport to the shoot of N from NO₃ absorbed over a 5–15 min period could be monitored when the external NO₃^? concentration ranged from 0–05 to 4 mol m^?3. NH₄⁺ as the N source labelled shoot tissue more slowly, and estimates of the transport between root and shoot could be made only with ¹³N. (3) Influx of NO₃^? into root tissue could be measured by ¹⁵N enrichment after 5–10 min at concentrations approaching the probable K_M of the high-affinity transport system. (4) There was some indication of isotope discrimination, especially with respect to the movement of labelled N to the shoot, when NO₃^? is the N source. For many purposes, ¹⁵N tracing can be used satisfactorily to estimate influxes of both NO₃^? and NH₄⁺ in soybean roots. Use of the short-lived radio nuclide ¹³N remains the method of choice for more refined measurements of internal distribution and assimilation.     

Glutathione metabolism in soybean callus-cultures as affected by salinity

Induction and growth of soybean callus cultures were influenced by NaCl, especially at the highest concentration tested (150 mM). Protein content was raised as NaCl was increased in the Murashige and Skoog medium. Total sulfhydryl group (-SH) and glutathione (GSH) concentrations were also increased in NaCl treated cultures. The affinity (Km) of glutathione reductase (GR) for oxidized glutathione (GSSG) was gradually increased as NaCl level was raised in the medium. The GSH/GSSG ratio was raised significantly as the result of GR activity. The increase in GR activity may constitute an adaptive response of soybean callus to NaCl. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic and cytological analyses of a partial-female-sterile mutant (PS-1) in soybean (Glycine max; Leguminosae)

Soybean partial-female-sterile mutant 1 (PS-1) was recovered from a gene-tagging study. The objectives were to study the inheritance, linkage, allelism, and certain aspects of the reproductive biology of the PS-1 mutant. For inheritance and linkage tests, PS-1 was crossed to flower color mutant Harosoy-w4 and to chlorophyll-deficient mutant CD-1, also recovered from the gene-tagging study. For allelism tests, reciprocal crosses were made with PS-1 and three other partial-sterile mutants (PS-2, PS-3, and PS-4) recovered from the same gene-tagging study. The PS-1 mutant is inherited in a 3:1 ratio and is a single recessive gene. Linkage results indicated that the gene for partial sterility in PS-1 is not linked either to the w4 locus or to the CD-1 locus. Allelism tests showed that the gene in PS-1 is nonallelic to the gene in PS-2, PS-3, and PS-4. Investigations of developing and mature pollen indicated no differences in morphology, stainability, or fluorescence between normal and partial-sterile genotypes. The PS-1 mutant is completely male fertile. Confocal scanning laser microscopy was used to determine that early embryo abortion in PS-1 is due indirectly to abnormal migration of the fused polar nucleus, which prevented it from being fertilized. Subsequent absence of endosperm development leads directly to abortion of the proembryo.     

Expression of fasciation mutation in apical meristems of soybean, Glycine max (Leguminosae)

The phenotype of the apical meristem was used to examine the effect of fasciation mutation at the f locus in different genetic backgrounds in soybean Glycine max (L.) Merr. Comparisons of meristem development in fasciation mutant and wild type were conducted with scanning electron microscope (SEM) on isogenic lines BARC-11-11-ff and BARC-11-11-FF at postgermination and early vegetative stages. Studies of apical meristems of three independently originated fasciation mutants, PI 83945-4, PI 243541, and T173, were carried out at vegetative and early floral transition stages. Corolla Fasciation, the extreme mutant phenotype, was used for comparison of meristem development. Enlargement of the apical meristem and shortened plastochron were observed in the mutant lines 2 d after germination. Similar to Corolla Fasciation, in PI 83945-4, PI 243541, and T173, enlargement of the apical meristem was followed by growth along one axis at the V3 stage and establishment of a ridge-like meristem at the V4 stage. Influence of pedigree on the expression of the fasciation phenotype was demonstrated by different growth patterns (subangular vs. ridge-like) of the apical meristem in BARC-11-11-ff and PI 243541 with the same f gene. During transition of the apical meristem from vegetative to reproductive stage in all mutant lines further production of leaf primordia ceased. The developmental pattern of the apical meristems suggests that the f locus may have the same allele in fasciation mutants of independent origin in soybean.     

Impact of Planting 'Bell', a Soybean Cultivar Resistant to Heterodera glycines, in Wisconsin

Although the soybean cyst nematode (SCN), Heterodera glycines, has been known to exist in Wisconsin for at least 14 years, relatively few growers sample for SCN or use host resistance as a means to manage this nematode. The benefit of planting the SCN-resistant cultivar Bell on a sandy soil in Wisconsin was evaluated in 1992 and 1993. A range of SCN population densities was achieved by planting 11 crops with varying degrees of susceptibility for 1 or 2 years before the evaluation. Averaged over nematode population densities, yield of ''Bell'' was 30 to 43% greater than that of the susceptible cultivars, ''Corsoy 79'' and ''BSR 101''. Counts of cysts collected the fall preceding soybean were more predictive of yield than counts taken at planting. Yields of all three cultivars were negatively related (P < 0.001) to cyst populations. Fewer (P < 0.01) eggs were produced on ''Bell'' than on the susceptible cultivars. The annual (fall to fall) change in cyst population densities was dependent on initial nematode density for all cultivars in 1992 and for the susceptible cultivars in 1993. Yield reductions induced by the SCN under the conditions of this study indicate that planting a SCN-resistant cultivar in Wisconsin can be beneficial if any cysts are detected.     

Effects of Zinc Fertilization of Corn on Hatching of Heterodera glycines in Soil

Experiments were conducted to determine the effects of zinc fertilizers on hatching and soil population densities of Heterodera glycines. In vitro egg hatching in solutions of reagent-grade zinc sulfate and zinc chloride and fertilizer-grade zinc sulfate was significantly greater than hatching in deionized water, whereas zinc chelate fertilizer significantly inhibited egg hatching relative to deionized water. In greenhouse experiments, no differences in cumulative percentage egg hatch were detected in soil naturally infested with H. glycines amended with fertilizer-grade zinc sulfate and zinc chelate at rates equivalent to 0, 1.12, 11.2, and 112 kg Zn/ha and subsequently planted with corn (Zea mays L.). In a field experiment, no significant differences in H. glycines egg population densities and corn yields were detected among plots fertilized with 0, 11.2, and 22.4 kg Zn/ha rates of zinc chelate. Yields of H. glycines-susceptible soybean planted in plots 1 year after zinc fertilization of corn plots also were not significantly affected. Zinc compounds significandy affected H. glycines egg hatching in vitro, but had no effect on hatching in natural soils.