Elevated CO<Subscript>2</Subscript> and virus infection impacts wheat and aphid metabolism

Introduction

The aphid Rhopalosiphum padi L. is a vector of Barley yellow dwarf virus (BYDV) in wheat and other economically important cereal crops. Increased atmospheric CO₂ has been shown to alter plant growth and metabolism, enhancing BYDV disease in wheat. However, the biochemical influences on aphid metabolism are not known.

Objectives

This work aims to determine whether altered host-plant quality, influenced by virus infection and elevated CO₂, impacts aphid weight and metabolism.

Methods

Untargeted ¹H NMR metabolomics coupled with multivariate statistics were employed to profile the metabolism of R. padi reared on virus-infected and non-infected (sham-inoculated) wheat grown under ambient CO₂ (aCO₂, 400 µmol mol^?1) and future, predicted elevated CO₂ (eCO₂, 650 µmol mol^?1) concentrations. Un-colonised wheat was also profiled to observe changes to host-plant quality (i.e., amino acids and sugars).

Results

The direct impacts of virus or eCO₂ were compared. Virus presence increased aphid weight under aCO₂ but decreased weight under eCO₂; whilst eCO₂ increased non-viruliferous (sham) aphid weight but decreased viruliferous aphid weight. Discriminatory metabolites due to eCO₂ were succinate and sucrose (in sham wheat), glucose, choline and betaine (in infected wheat), and threonine, lactate, alanine, GABA, glutamine, glutamate and asparagine (in aphids), irrespective of virus presence. Discriminatory metabolites due to virus presence were alanine, GABA, succinate and betaine (in wheat) and threonine and lactate (in aphids), irrespective of CO₂ treatment.

Conclusion

This study confirms that virus and eCO₂ alter host-plant quality, and these differences are reflected by aphid weight and metabolism.

     

Use of spectral analysis to test hypotheses on the origin of pinnipeds

The evolutionary origin of the pinnipeds (seals, sea lions, and walruses) is still uncertain. Most authors support a hypothesis of a monophyletic origin of the pinnipeds from a caniform carnivore. A minority view suggests a diphyletic origin with true seals being related to the mustelids (otters and ferrets). The phylogenetic relationships of the walrus to other pinniped and carnivore families are also still particularly problematic. Here we examined the relative support for mono- and diphyletic hypotheses using DNA sequence data from the mitochondrial small subunit (12S) rRNA and cytochrome b genes. We first analyzed a small group of taxa representing the three pinniped families (Phocidae, Otariidae, and Odobenidae) and caniform carnivore families thought to be related to them. We inferred phylogenetic reconstructions from DNA sequence data using standard parsimony and neighbor-joining algorithms for phylogenetic inference as well as a new method called spectral analysis (Hendy and Penny) in which phylogenetic information is displayed independently of any selected tree. We identified and compensated for potential sources of error known to lead to selection of incorrect phylogenetic trees. These include sampling error, unequal evolutionary rates on lineages, unequal nucleotide composition among lineages, unequal rates of change at different sites, and inappropriate tree selection criteria. To correct for these errors, we performed additional transformations of the observed substitution patterns in the sequence data, applied more stringent structural constraints to the analyses, and included several additional taxa to help resolve long, unbranched lineages in the tree. We find that there is strong support for a monophyletic origin of the pinnipeds from within the caniform carnivores, close to the bear/raccoon/panda radiation. Evidence for a diphyletic origin was very weak and can be partially attributed to unequal nucleotide compositions among the taxa analyzed. Subsequently, there is slightly more evidence for grouping the walrus with the eared seals versus the true seals. A more conservative interpretation, however, is that the walrus is an early, but not the first, independent divergence from the common pinniped ancestor.      

Oxygen metabolism,oxidative stress and acid-base physiology of dental plaque biofilms

Dental plaque is a natural biofilm which has been a focus of attention for many years because of its known roles in caries and periodontal diseases. Acid production by plaque bacteria leads to the erosion of tooth mineral in caries, and the cariogenicity of plaque is related to population levels of acid-tolerant organisms such as mutants streptococci. However, the biofilm character of plaque allows for survival of a diverse flora, including less acid-tolerant organisms, some of which can produce ammonia from arginine or urea to counter acidification. Plaque is often considered to be relatively anaerobic. However, evidence is presented here that both supragingival and subgingival plaque have active oxygen metabolism and that plaque bacteria, including anaerobes, have developed defenses against oxidative stress. Even in subgingival plaque associated with periodontitis, measured residual oxygen levels are sufficient to allow for oxygen metabolism by organisms considered to be extremely anaerobic such asTreponema denticola, which metabolizes oxygen by means of NADH oxidases and produces the protective enzymes superoxide dismutase and NADH peroxidase. The finding that plaque bacteria produce a variety of protective enzymes is a good indicator that oxidative stress is a part of their everyday life. The biofilm character of plaque allows for population diversity and coexistence of aerobes, anaerobes and microaerophiles. Overall, agents that affect oxidative metabolism offer possibilities for reducing the pathogenic activities of plaque.     

Site selection by swans wintering in Britain and Ireland; the importance of habitat and geographic location

Monthly surveys of Bewick's Swans Cygnus columbianus bewickii , Whooper Swans Cygnus cygnus and Mute Swans Cygnus olor in Britain and Ireland were made during the 1990–1991 winter to determine factors affecting the swans' selection of feeding sites. Geographic location and habitat both influenced site selection. Whooper Swans occurred in greatest numbers at sites in Scotland, northeastern England and Northern Ireland, whereas Bewick's Swans had a more southerly distribution, reflecting differences in the migratory routes used by these two species. The resident Mute Swans were more widespread, with large flocks occurring in southeastern England and in parts of Scotland. Whooper and Mute Swans were found mainly on permanent inland waters (68% and 61%, respectively), but the majority of Bewick's Swans (60%) were on arable land. The percentage of Bewick's Swan flocks found on permanent inland waters (42%) was higher than that found on arable fields (23%), indicating that the large number recorded on arable land was a result of the birds congregating at a comparatively small number of sites. Overall, less than 15% of Whooper Swans and 3% of Mute Swans were on arable crops during the winter, but the largest flocks were associated with arable land for all three species. Thus, although the occurrence of large flocks at particular arable sites may give an impression that swans feed mainly on farmland, the swans are in fact more widely dispersed. Regional variation in the percentage of juveniles present was recorded for all three species. Changes during the winter in the distribution of juveniles, and of the swans as a whole, are considered in relation to food supply and to migratory routes for the Bewick's and Whooper Swans.     

Chromosomal localization of a tandemly repeated DNA sequence in Trifolium repens L

INTRoDUCTIoNlYho1iumrePensL,whiteclover,isaneconomicallyimportantplantspeciesintemperatepastures.Asbrieflyreportedby[1],ithas16pairsofchromosomes(2n=32).Asyet,nodetailedcytologicalexaminationofthisspecies,suchasC-banding,hasbeenrep0rted.Inthelastdecade,thetechnique0fC-bandinghasbeenusedt0examinehighlyrepeatedsequencesinplantchrom0s0mesandhasprovidedausefultoolf0rtheanalysis0fcyt0geneticstructureincr0pplants[2-71.Inplants,thechr0m0s0mall0calizationofhighlyrepeatedDNAsequencesbyinsituhybr…     

Elementary properties and pharmacological sensitivities of calcium channels in mammalian peripheral neurons

The major component of whole-cell Ca2+ current in differentiated, neuron-like rat pheochromocytoma (PC12) cells and sympathetic neurons is carried by dihydropyridine-insensitive, high-threshold-activated N-type Ca2+ channels. We show that these channels have unitary properties distinct from those of previously described Ca2+ channels and contribute both slowly inactivating and large sustained components of whole-cell current. The N-type Ca2+ currents are modulated by GTP binding proteins. The snail toxin omega-conotoxin reveals two pharmacological components of N-type currents, one blocked irreversibly and one inhibited reversibly. Contrary to previous reports, neuronal L-type channels are insensitive to omega-conotoxin. N-type Ca2+ channels appear to be specific for neuronal cells, since their functional expression is greatly enhanced by nerve growth factor.     

Plasma immunoreactive beta-melanocyte-stimulating hormone and skin pigmentation in chronic renal failure.

Plasma immunoreactive beta-melanocyte stimulating hormone (beta-MSH) concentrations were greatly increased in patients with chronic renal failure. There was no correlation between the severity of the renal failure or the degree of pigmentation and the plasma beta-MSH levels.     

Type 1 and Type 2 Herpes Simplex Viruses: Serological and Biological Differences

Forty isolates of herpes simplex virus were compared by means of cross-neutralization curves. The 11 oral isolates were serotype 1, and all 29 genital/anal isolates were serotype 2. The cytopathic effects of the two serotypes were consistently different. Passage of strains of type 1 and type 2 in mice and in rabbits yielded two variants, although the majority of the strains remained unchanged serologically and in their cytopathic effects. The two variants were derived from type 1 strains and differed from the parent strains in their cytopathic effects, each of them producing syncytia and enlarged plaques. They had, however, retained the serotypic properties and the deoxyribonucleic acid (DNA) densities of their parent strains. The Roizman syncytial/macroplaque strain of herpes simplex virus was also included in the study; the density of its DNA (1.727 g/ml) was typical of type 1 strains, and serologically it seemed to be basically a type 1 strain, although it was neutralized by type 2 antiserum slightly better than were other type 1 strains. Growth curves were performed of the two serotypes in rabbit kidney, human fibroblast, and mouse embryo tissue cultures. The type 2 strains attained lower titers of infectivity in these three cell systems; the levels of infectivity of type 2 virus in the culture fluid decreased much more rapidly after the maximum had been attained than did the levels of infectivity of the type 1 strains, due to the greater instability of the type 2 virus. Parallel titrations of different strains in tissue cultures and intracerebrally in mice indicated that the latter assay system was usually more sensitive for type 2 strains than it was for type 1 strains. The paralytic sequelae and inflammatory changes of lumbar ganglia and spinal cord in young rabbits inoculated extraneurally with strains of the two serotypes also indicate that the type 2 virus is more virulent in laboratory animals than is type 1 virus.     

Mesosecrin: a secreted glycoprotein produced in abundance by human mesothelial, endothelial, and kidney epithelial cells in culture

Human mesothelial cells, endothelial cells, and type II kidney epithelial cells growing in culture devote approximately 3% of their total protein synthesis to the production of an Mr approximately 46-kD, pI 7.1, secreted glycoprotein (designated Sp46). Fibroblasts make about 1/10th as much Sp46 as these cell types, and their synthesis is dependent upon hydrocortisone. Keratinocytes, urothelial cells, conjunctival epithelial cells, and mammary epithelial cells do not make detectable amounts of Sp46. Mesothelial cells secrete Sp46 onto the substratum, and from there it is subsequently released into the medium. Immunofluorescence analysis using specific antisera discloses that Sp46 is deposited beneath cells as a fine coating on the substratum. In sparse cultures, Sp46 is detected in trails behind motile cells. In contrast, secreted fibronectin coalesces into fibers, most of which remain in contact with and on top of the cells; thus Sp46 does not preferentially bind to fibronectin. About 6 kD of the mass of human Sp46 is N-linked oligosaccharide, which is terminally sialated before secretion. Sp46 has a low glycine content, indicating that it is not a collagenlike protein. Its NH2-terminal sequence over the first 40 amino acids does not resemble any protein for which sequence information is available. Sp46 appears to be a novel extracellular glycoprotein, high-level constitutive expression of which is restricted to mesoderm-derived epithelial and endothelial cells. We therefore propose for it the name "mesosecrin."