Genbank accession #: 133708

Plant Molecular Biology -     

Comparison of photosynthesis and productivity of Gunnera tinctoria Molina (Mirbel) with and without the phycobiont Nostoc punctiforme L.

Abstract. Marked increases in growth and nitrogen content were found with Gunnera tinctoria Molina (Mirbel) plants infected (+ Nostoc ) with the cyanobacterium Nostoc punctiforme L., in comparison to uninfected (— Nostoc ) plants and this was attributed to N₂-fixation by the phycobiont. Whilst host and symbiont can be grown separately, preliminary data indicates that the host plant is reliant on the cyanobacterium to meet its nitrogen requirements because it has little capacity to assimilate nitrate. Although the maximum light-saturated rate of photosynthesis was higher in the + Nostoc plants, there was no reduction in photosynthetic efficiency under lightlimiting conditions, despite marked differences in plant nitrogen status. Differences in photosynthetic rate were implicated as the major reason for the differences in plant productivity. Stomatal conductance was insensitive to changes in plant nitrogen status and did not parallel the variation in photosynthetic rates. The ecological significance of the largely invariant stomatal response and the consequences of differences in water and nitrogen-use efficiencies between + and — Nostoc plants is discussed.     

Screening of Feral Pigeon (Colomba livia), Mallard (Anas platyrhynchos) and Graylag Goose (Anser anser) Populations for Campylobacter spp., Salmonella spp., Avian Influenza Virus and Avian Paramyxovirus

A total of 119 fresh faecal samples were collected from graylag geese migrating northwards in April. Also, cloacal swabs were taken from 100 carcasses of graylag geese shot during the hunting season in August. In addition, samples were taken from 200 feral pigeons and five mallards. The cultivation of bacteria detected Campylobacter jejuni jejuni in six of the pigeons, and in one of the mallards. Salmonella diarizona 14:k:z53 was detected in one graylag goose, while all pigeons and mallards were negative for salmonellae. No avian paramyxovirus was found in any of the samples tested. One mallard, from an Oslo river, was influenza A virus positive, confirmed by RT-PCR and by inoculation of embryonated eggs. The isolate termed A/Duck/Norway/1/03 was found to be of H3N8 type based on sequence analyses of the hemagglutinin and neuraminidase segments, and serological tests. This is the first time an avian influenza virus has been isolated in Norway. The study demonstrates that the wild bird species examined may constitute a reservoir for important bird pathogens and zoonotic agents in Norway.     

Using Genetic Tools to Track Desert Bighorn Sheep Colonizations

ABSTRACT Understanding colonization is vital for managing fragmented populations. We employed mitochondrial DNA haplotypes and 14 microsatellite (nuclear DNA) markers to infer the origins of newly established populations of desert bighorn sheep (Ovis canadensis nelsoni) and to assess loss of genetic diversity during natural colonizations. We used haplotype distribution, F-statistics, Bayesian population clustering, and assignment tests to infer source populations for 3 recent colonies and identified a previously undetected colonization from multiple source populations. Allelic richness declined in 3 of 4 colonies in comparison to the primary source populations, but not as much as has been reported for translocated populations. Heterozygosity declined in only one colony. We also demonstrated that both native and translocated desert bighorn sheep have naturally recolonized empty habitats and suggest that colonization may partially offset population extinction in the region as long as connectivity is maintained. Genetic techniques and mitochondrial DNA haplotypes we described will allow managers to determine the origins of future colonizations by bighorn sheep in California, USA, and prioritize protection of linkages between known sources and colonies.     

Properties of Extracellular Enzymes from Aphanomyces astaci and Their Relevance in the Penetration Process of Crayfish Cuticle

In culture filtrates from the crayfish plague parasite, Aphanomyces astaci, protease and a low level of hyaluronidase activity were found. The hyaluronidase activity was highest at pH 6.5 or above and at about 23°C. The protease activity had a broad pH-optimum, between pH 7 and at least pH 10, and was partially denatured at 30°C. However, when incubated for 30 min with the substrate, casein, the activity increased logarithmically up to about 35–40°C and had an apparent optimum at 45–50°C. The proteases from the parasitic as well as from two less proteolytic, saprophytic Aphanomyces species were predominantly constitutive and were excreted mainly by the older mycelia. Proteases from the parasite and a saprophyte did not reach full activity until 10–30 min after substrate addition. No lipase activity was found in the case of the mycelium of the parasitic species. However, esterase was apparently present inside germinating zoospores. The native enzymes of A. astaci could degrade freeze-dried soft cuticle from crayfish. The relevance of the different enzymes of A. astaci for the penetration process within the cuticle of crayfish is discussed.     

Studies on l-glutamate in insect haemolymph.

ABSTRACT. The neuromuscular junctions of abdominal body wall muscles of larval Lucilia sericata are mainly superficial, with no glial sheath, and are surrounded by a well-developed subsynaptic reticulum. Injection of l -glutamate into the haemolymph of adult male Locusta migratoria and larvae of Lucilia sericata caused reversible effects on motor activity. These effects were quantified and dose—response curves are presented. The effective concentration of the injected doses is low enough to be physiologically relevant. Injection of l -aspartate into Locusta haemolymph affected motor activity. Injection of l -aspartate into Lucilia larvae produced no detectable effect. Injections combining l -aspartate and l -glutamate into Lucilia larvae had a synergistic effect on the duration of paralysis, compared with the same concentration of l -glutamate injected alone.