Liming and deep ripping responses for a range of field crops

Grain yields were measured over 2 seasons from a range of field crops following liming and deep ripping an acid and compacted soil in north-eastern Victoria. Lime (2.5 t ha^–1) substantially reduced the level of exchangeable Al and exchangeable Mn whilst raising soil pH by about 1.0 unit. The crops grown were 7 cultivars of wheat and one cultivar each of triticale, oats, barley, rapeseed, safflower, field pea, chick pea and lupins. With the exception of lupin, liming the soil increased (p=0.05) the grain yield of all crops and cultivars. With the wheat cultivars there were 2 distinct groups with different tolerance to soil acidity. Wheat, oats, triticale and lupins had higher absolute yields than the other crops. Safflower and chick pea had very low yields without soil amendment. The magnitude of the lime response did not differ between the wheat cultivars (17%) or between any of the crop species (range 9–29%). Deep ripping the soil to break a hard compacted layer resulted in more yield for all the cereals and safflower. The results demonstrate the importance of using crops with tolerance to acid soil conditions as well as gains that can be obtained with ameliorating identifiable soil problems.     

TheRT1.G locus in the rat encodes a Qa/TL-like antigen

A new antigenic system in the rat homologous to theQa/TL antigen system in the mouse has been characterized. It was detected by antibodies raised in donor-recipient combinations that were matched for theRT1. A, B, D, E loci in the major histocompatibility complex (MHC): (R11×BN)F₁ anti-BN.1L(LEW), (R18×BN)F₁ anti-BN.1L, and BN.1LV1(F344) anti-BN.1L. Absorption analyses using these antisera and a variety of inbred, congenic and recombinant strains identified three alleles,RT1.G ^a ,G ^b ,G ^c , of whichG ^c is a null allele. The strain distribution of these alleles was determined, using 37 strains of rats representative of all of the prototypic haplotypes and a number of congenic and recombinant strains. The use of the congenic and recombinant strains showed that theRT1.G locus was linked to the MHC and that the most probable gene order wasA-E-G. Testcross analysis showed that the map distance betweenA andG was 1.4 cM(4/285 recombinants). The RT1.G antigen has a heavy chain ofM _r 46 000 and is present on both T and B cells.     

Mapping in the mouse of the region homologous to the rat growth and reproduction complex (grc)

Offprint requests: J. Klein.     

Regulated copper uptake in Chlamydomonas reinhardtii in response to copper availability.

A saturable and temperature-dependent copper uptake pathway has been identified in Chlamydomonas reinhardtii. The uptake system has a high affinity for copper ions (Km approximately 0.2 microM) and is more active in cells that are adapted to copper deficiency than to cells grown in a medium containing physiological (submicromolar to micromolar) copper ion concentrations. The maximum velocity of copper uptake by copper-deficient cells (169 pmol h-1 10(6) cells-1 or 62 ng min-1 mg-1 chlorophyll) is up to 20-fold greater than that of fully copper-supplemented cells, and the Km (approximately 2 x 10(2) nM) is unaffected. Thus, the same uptake system appears to operate in both copper-replete and copper-deficient cells, but its expression or activity must be induced under copper-deficient conditions. A cupric reductase activity is also increased in copper-deficient compared with copper-sufficient cells. The physiological characteristics of the regulation of this cupric reductase are compatible with its involvement in the uptake pathway. Despite the operation of the uptake pathway under both copper-replete and copper-deficient conditions, C. reinhardtii cells maintained in fully copper-supplemented cells do not accumulate copper in excess of their metabolic need. These results provide evidence for a homeostatic mechanism for copper metabolism in C. reinhardtii.     

The prospects of poop: a review of past achievements and future possibilities in faecal isotope analysis

What can the stable isotope values of human and animal faeces tell us? This often under-appreciated waste product is gaining recognition across a variety of disciplines. Faecal isotopes provide a means of monitoring diet, resource partitioning, landscape use, tracking nutrient inputs and cycling, and reconstructing past climate and environment. Here, we review what faeces are composed of, their temporal resolution, and how these factors may be impacted by digestive physiology and efficiency. As faeces are often used to explore diet, we clarify how isotopic offsets between diet and faeces can be calculated, as well as some differences among commonly used calculations that can lead to confusion. Generally, faecal carbon isotope (δ¹³C) values are lower than those of the diet, while faecal nitrogen isotope values (δ¹⁵N) values are higher than in the diet. However, there is considerable variability both within and among species. We explore the role of study design and how limitations stemming from a variety of factors can affect both the reliability and interpretability of faecal isotope data sets. Finally, we summarise the various ways in which faecal isotopes have been applied to date and provide some suggestions for future research. Despite remaining challenges, faecal isotope data are poised to continue to contribute meaningfully to a variety of fields.     

Effects of temperature and nutrients on microscopic stages of the bull kelp (Nereocystis luetkeana,Phaeophyceae)

Warming ocean temperatures have been linked to kelp forest declines worldwide, and elevated temperatures can act synergistically with other local stressors to exacerbate kelp loss. The bull kelp Nereocystis luetkeana is the primary canopy-forming kelp species in the Salish Sea, where it is declining in areas with elevated summer water temperatures and low nutrient concentrations. To determine the interactive effects of these two stressors on microscopic stages of N. luetkeana, we cultured gametophytes and microscopic sporophytes from seven different Salish Sea populations across seven different temperatures (10–22°C) and two nitrogen concentrations. The thermal tolerance of microscopic gametophytes and sporophytes was similar across populations, and high temperatures were more stressful than low nitrogen levels. Additional nitrogen did not improve gametophyte or sporophyte survival at high temperatures. Gametophyte densities were highest between 10 and 16°C and declined sharply at 18°C, and temperatures of 20 and 22°C were lethal. The window for successful sporophyte production was narrower, peaking at 10–14°C. Across all populations, the warmest temperature at which sporophytes were produced was 16 or 18°C, but sporophyte densities were 78% lower at 16°C and 95% lower at 18°C compared to cooler temperatures. In the field, bottom temperatures revealed that the thermal limits of gametophyte growth (18°C) and sporophyte production (16–18°C) were reached during the summer at multiple sites. Prolonged exposure of bull kelp gametophytes to temperatures of 16°C and above could limit reproduction, and therefore recruitment, of adult kelp sporophytes.     

Cloning and characterization of the katB gene of Pseudomonas aeruginosa encoding a hydrogen peroxide-inducible catalase: purification of KatB, cellular localization, and demonstration that it is essential for optimal resistance to hydrogen peroxide.

Pseudomonas aeruginosa is an obligate aerobe that is virtually ubiquitous in the environment. During aerobic respiration, the metabolism of dioxygen can lead to the production of reactive oxygen intermediates, one of which includes hydrogen peroxide. To counteract the potentially toxic effects of this compound, P. aeruginosa possesses two heme-containing catalases which detoxify hydrogen peroxide. In this study, we have cloned katB, encoding one catalase gene of P. aeruginosa. The gene was cloned on a 5.4-kb EcoRI fragment and is composed of 1,539 bp, encoding 513 amino acids. The amino acid sequence of the P. aeruginosa katB was approximately 65% identical to that of a catalase from a related species, Pseudomonas syringae. The katB gene was mapped to the 71- to 75-min region of the P. aeruginosa chromosome, the identical region which harbors both sodA and sodB genes encoding both manganese and iron superoxide dismutases. When cloned into a catalase-deficient mutant of Escherichia coli (UM255), the recombinant P. aeruginosa KatB was expressed (229 U/mg) and afforded this strain resistance to hydrogen peroxide nearly equivalent to that of the wild-type E. coli strain (HB101). The KatB protein was purified to homogeneity and determined to be a tetramer of approximately 228 kDa, which was in good agreement with the predicted protein size derived from the translated katB gene. Interestingly, KatB was not produced during the normal P. aeruginosa growth cycle, and catalase activity was greater in nonmucoid than in mucoid, alginate-producing organisms. When exposed to hydrogen peroxide and, to a greater extent, paraquat, total catalase activity was elevated 7- to 16-fold, respectively. In addition, an increase in KatB activity caused a marked increase in resistance to hydrogen peroxide. KatB was localized to the cytoplasm, while KatA, the "housekeeping" enzyme, was detected in both cytoplasmic and periplasmic extracts. A P. aeruginosa katB mutant demonstrated 50% greater sensitivity to hydrogen peroxide than wild-type bacteria, suggesting that KatB is essential for optimal resistance of P. aeroginosa to exogenous hydrogen peroxide.     

Neonatal DNA immunization with a plasmid encoding an internal viral protein is effective in the presence of maternal antibodies and protects against subsequent viral challenge.

Conventional vaccines are remarkably effective in adults but are much less successful in the very young, who are less able to initiate a mature immune response and who may carry maternal antibodies which inactivate standard vaccines. We set out to determine whether DNA immunization might circumvent these problems. We have previously shown that intramuscular injection of plasmid DNA encoding the nucleoprotein (NP) gene of lymphocytic choriomeningitis virus (LCMV) is capable of inducing immune responses and protecting 50% of adult mice against lethal and sublethal challenge with LCMV. Here we demonstrate that mouse pups injected with the same plasmid hours or days after birth produce major histocompatibility complex-restricted, NP-specific cytotoxic T lymphocytes (CTL) that persist into adulthood; 48% of vaccinated pups responded to subsequent sublethal viral challenge by the accelerated production of anti-NP LCMV-specific CTL, indicating that these animals had been successfully immunized by the plasmid DNA. In addition, these mice showed a >95% reduction in splenic viral titers 4 days postinfection compared to control mice, demonstrating a more rapid control of infection in vivo. Furthermore, pups born of and suckled on LCMV-immune dams (and therefore containing passively acquired anti-LCMV antibodies at the time of DNA inoculation) responded to the DNA vaccine in a similar manner, showing that maternally derived anti-LCMV antibodies do not significantly inhibit the generation of protective immune responses following DNA vaccination. These findings suggest that, at least in this model system, DNA immunization circumvents many of the problems associated with neonatal immunization.     

Purification and characterization of the 180- and 86-kilodalton subunits of the Saccharomyces cerevisiae DNA primase-DNA polymerase protein complex. The 180-kilodalton subunit has both DNA polymerase and 3'----5'-exonuclease activities.

The yeast Saccharomyces cerevisiae catalytic DNA polymerase I 180-kDa subunit and the tightly associated 86-kDa polypeptide have been purified using immunoaffinity chromatography, permitting further characterization of the DNA polymerase activity of the DNA primase-DNA polymerase protein complex. The subunits were purified to apparent homogeneity from separate overproducing yeast strains using monoclonal antibodies specifically recognizing each subunit. When the individual subunits were recombined in vitro a p86p180 physical complex formed spontaneously, as judged by immunoprecipitation of 180-kDa polypeptide and DNA polymerase activity with the anti-86-kDa monoclonal antibody. The 86-kDa subunit stabilized the DNA polymerase activity of the 180-kDa catalytic subunit at 30 degrees C, the physiological temperature. The apparent DNA polymerase processivity of 50-60 nucleotides on poly(dA).oligo(dT)12 or poly(dT).oligo(A)8-12 template-primer was not affected by the presence of the 86-kDa subunit but was reduced by increased Mg2+ concentration. The Km of the catalytic 180-kDa subunit for dATP or DNA primer terminus was unaffected by the presence of the 86-kDa subunit. The isolated 180-kDa polypeptide was sufficient to catalyze all the DNA synthesis that had been observed previously in the DNA primase-DNA polymerase protein complex. The 180-kDa subunit possessed a 3'----5'-exonuclease activity that catalyzed degradation of polynucleotides, but degradation of oligonucleotide substrates of chain lengths up to 50 was not detected. This exonuclease activity was unaffected by the presence of the 86-kDa subunit. Despite the striking physical similarity of the DNA primase-DNA polymerase protein complex in all eukaryotes examined, the data presented here indicate differences in the enzymatic properties detected in preparations of the DNA polymerase subunits isolated from S. cerevisiae as compared with the properties of preparations from Drosophila cells. In particular, the 3'----5'-exonuclease activity associated with the yeast catalytic DNA polymerase subunit was not masked by the 86-kDa subunit.