Overwintering squash bugs harbor and transmit the causal agent of cucurbit yellow vine disease

Since 1988, cucurbit crops, particularly watermelon, cantaloupe, and squash, grown in Oklahoma and Texas have experienced devastating losses from cucurbit yellow vine disease (CYVD), caused by the phloem-limited bacterium Serratia marcescens Bizio. Squash bug, Anasa tristis (De Geer), is a putative vector of the pathogen. In 2000-2001, overwintering populations of squash bug collected from DeLeon, TX, were tested for their ability to harbor and transmit the bacterium. Individual squash bugs (n = 73) were caged serially for periods of up to 7 d on at least four squash seedlings. Two studies were conducted, one with insects collected in November 2000 placed on first true leaf-stage seedlings and the second with insects from an April 2001 collection, placed on 3-5 true leaf-stage squash. Controls consisted of squash seedlings caged without insects. Squash bug transmission rates of the pathogen in studies I and II were 20 and 7.5%, respectively. Overall, 11.0% of the squash bugs harbored and successfully transmitted the bacterium to squash seedlings. All control plants tested negative for S. marcescens and did not exhibit CYVD. Female squash bugs killed a significantly greater proportion of young first leaf-stage seedlings than males. Feeding on 3-5 leaf-stage squash resulted in no plant mortality regardless of squash bug gender. This study demonstrated that the squash bug harbors S. marcescens in its overwintering state. The squash bug-S. marcescens overwintering relationship reported herein greatly elevates the pest status of squash bug and places more importance on development of integrated strategies for reducing potential overwintering and emerging squash bug populations.     

Forskolin-induced apical membrane insertion of virally expressed, epitope-tagged CFTR in polarized MDCK cells

Channel gating ofthe cystic fibrosis transmembrane conductance regulator (CFTR) isactivated in response to cAMP stimulation. In addition, CFTR activationmay also involve rapid insertion of a subapical pool of CFTR into theplasma membrane (PM). However, this issue has been controversial, inpart because of the difficulty in distinguishing cell surface vs.intracellular CFTR. Recently, a fully functional, epitope-tagged formof CFTR (M2-901/CFTR) that can be detected immunologically innonpermeabilized cells was characterized (Howard M, Duvall MD,Devor DC, Dong J-Y, Henze K, and Frizzell RA. Am J PhysiolCell Physiol 269: C1565-C1576, 1995; and Schultz BD,Takahashi A, Liu C, Frizzell RA, and Howard M. Am J PhysiolCell Physiol 273: C2080-C2089, 1997). We have developedreplication-defective recombinant adenoviruses that expressM2-901/CFTR and used them to probe cell surface CFTR in forskolin(FSK)-stimulated polarized Madin-Darby canine kidney (MDCK) cells.Virally expressed M2-901/CFTR was functional and was readilydetected on the apical surface of FSK-stimulated polarized MDCK cells.Interestingly, at low multiplicity of infection, we observedFSK-stimulated insertion of M2901/CFTR into the apical PM, whereas athigher M2-901/CFTR expression levels, no increase in surfaceexpression was detected using indirect immunofluorescence. Immunoelectron microscopy of unstimulated and FSK-stimulated cells confirmed the M2-901/CFTR redistribution to the PM upon FSKstimulation and demonstrates that the apically insertedM2-901/CFTR originates from a population of subapical vesicles.Our observations may reconcile previous conflicting reports regardingthe effect of cAMP stimulation on CFTR trafficking.

     

Identification of cytomegalovirus-specific cytotoxic T lymphocytes in vitro is greatly enhanced by the use of recombinant virus lacking the US2 to US11 region or modified vaccinia virus Ankara expressing individual viral genes

Cytomegalovirus (CMV) elicits a potent T-cell response in humans that appears to protect the host from virus-associated disease. Despite facing strong host defense mechanisms, CMV remains as a lifelong infection that may reactivate and cause life-threatening disease in immunocompromised individuals. This persistence is probably assisted by expression of immune subversion proteins of the virus encoded by genes belonging to the US gene family. These proteins modulate major histocompatibility complex expression in infected cells and bias in vitro experiments toward the detection of only certain specificities. We have combined the use of recombinant CMV, lacking the US2 to US11 region genes, and cytoplasmic gamma interferon staining to define a more accurate assessment of CMV-specific responses in vivo. Recombinant CMV stimulation reveals a CD8 response much larger than that of parental virus in all donors tested. In some cases, this represented up to 10-fold increases in the number of cells detected. Responses were directed mainly against pp65, IE-1, and pp50 in the majority of donors. In addition, previously unreported IE-2-specific T-cell responses could be detected in a minority of cases. Furthermore, we observed a less marked increase in the response to mutant CMV by CD4 T cells in some donors. This suggests that a much broader T-cell response to CMV exists in vivo than is revealed by restimulation with wild-type virus and adds to the evidence that the efficacy of immune evasion strategies may not be as absolute as previously believed.     

The proportion of different eco-ethological sections of reproductive guilds of fishes in some African inland waters

Synopsis The continent of Africa has a wide variety of inland waters ranging from rift valley lakes to endorheic and coastal lakes, floodplains and rivers. This paper makes a preliminary comparison of the number of species in different eco-ethological sections of the reproductive guild categories of non-guarders, guarders and bearers in ancient African Great Lakes (Malawi, Victoria and Tanganyika), fluctuating endorheic lakes (Ngami, Chad and Chilwa), typical rivers (Orange-Vaal, Limpopo, Phongolo, Sabi-Lundi, Middle and Lower Zambezi, Kafue, Cunene, Okavango, Niger, Luongo, Lower Zaire) and wetlands (Okavango Delta and Kafue floodplain). The results indicate that the highest percentage of bearers and guarders is found in the ancient African Great Lakes, which are characterised by relatively predictable physico-chemical regimes, whereas a higher percentage of non-guarders is found in the rivers and wetlands, which have less predictable physico-chemical regimes. The management implications of this observation are discussed, and the usefulness of the species as a unit in ecology is assessed.     

The importance of underground shelter resources for reptiles in dryland landscapes: A woma python case study

For effective fauna conservation and management, ecologists are required to identify the resources that are critical for species to survive, and consider how these are distributed across landscapes. The critical resources usually considered are food and water, but the availability of appropriate shelter resources can be a key driver of habitat suitability for terrestrial reptiles and amphibians. Reptiles are important components of dryland ecosystems, yet we have little understanding about how anthropogenic disturbances affect the availability of shelter resources and reptile survival in drylands. In this study, we used VHF radio‐tracking to assess the importance of shelter resources in determining the habitat use patterns of a Near‐Threatened reptile species, the woma (Aspidites ramsayi; Pythonidae), in modified and intact dryland landscapes of Queensland, Australia. We compared the structural and thermal attributes of locations that were used, with those that were available. Using an information‐theoretic approach, we found that the occurrence of womas was strongly associated with the presence of ground burrows, which are excellent thermal insulators. No other shelter type was capable of buffering our study species from sub‐zero temperatures during winter, although summer temperatures of >40°C were buffered by hollow logs and piles of woody debris. Habitat use patterns were influenced more by the occurrence of underground shelters than by habitat type. Clearing status per se (cleared, regrowth or intact) had minimal influence on occurrence. Thermally buffered underground shelters are a vital resource for our focal species, and the availability of this shelter resource drives habitat suitability in modified dryland landscapes. Due to the key trophic role of reptiles in dryland ecosystems, and the excellent thermal buffering capacity of underground shelters, we propose that ground burrows may be potentially considered as keystone structures in drylands, and require a similar level of protection to ‘habitat’ or ‘legacy’ trees in forested ecosystems.     

The effects of suspensoids on fish

High suspensoid loads are a common feature of many Southern Hemisphere inland waters. Case studies on a natural lake (Chilwa), a man-made lake (Le Roux) and S.W. Indian Ocean estuaries reveal that the effects of turbidity on fish in these systems differ widely. In Lake Le Roux, high suspensoid loads influence fish by causing a reduced growth rate, a decrease in size at first maturity and maximum size, and a movement inshore by large fishes to feed on phytobenthos. High turbidities in Lake Chilwa sharply reduce food availability in benthic offshore zones, and restrict fishes to pelagic and inshore food resources. The resuspension of sediments by wind action may cause fish mortalities through deoxygenation of the water column. Moderate turbidity levels appear to be beneficial to fish in estuaries by affording protection from predators in shallow, food-rich areas. Turbidity gradients may also provide a navigational aid to fish entering estuaries.While ecological studies on Southern Hemisphere inland waters are fairly advanced, experimental work is restricted. Such research in the Northern Hemisphere has revealed that high suspensoid loads may influence breeding success, egg and larval survival, population structure and size, as well as food availability and feeding efficiency. The effect of suspensoids on the breeding success and feeding efficiency of Southern Hemisphere fish needs further investigation.Moderate suspensoid loads are a natural feature of many inland waters, but sustained high levels reduce the photic zone, blanket the benthos and interfere with the feeding efficiency of fish. The curtailment of soil erosion should therefore be regarded as a priority in the management of inland fisheries, especially in Third World countries where poor land-use practises have resulted in a marked deterioration of water quality. The need to study and manage river catchments holistically is emphasized.     

IMPLICATIONS OF WATER RELEASE FROM THE PONGOLAPOORT DAM FOR THE FISH AND FISHERY OF THE PHONGOLO FLOODPLAIN,ZULULAND

Summary

Wetland fish stocks can usually be sustained as long as the natural flood regime is maintained, but unnatural disruption of the flooding pattern can interfere with fish spawning and feeding. The dynamics of the Phongolo floodplain fish community are determined by periodically changing abiotic factors, especially water level and water temperature, and biotic factors, especially food availability. Water level fluctuations have several important functions and result in pulses of nutrient input and fish abundance. This paper examines the implications of the timing, magnitude and duration of simulated flood releases from the Pongolapoort Dam on the downstream fish and fishery.     

What's in a name; Genetic structure in Solanum section Petota studied using population-genetic tools

Background  

The taxonomy and systematic relationships among species of Solanum section Petota are complicated and the section seems overclassified. Many of the presumed (sub)species from South America are very similar and they are able to exchange genetic material. We applied a population genetic approach to evaluate support for subgroups within this material, using AFLP data. Our approach is based on the following assumptions: (i) accessions that may exchange genetic material can be analyzed as if they are part of one gene pool, and (ii) genetic differentiation among species is expected to be higher than within species.     

Synergizing metabolic flux analysis and nucleotide sugar metabolism to understand the control of glycosylation of recombinant protein in CHO cells

Background

The photorespiratory nitrogen cycle in C₃ plants involves an extensive diversion of carbon and nitrogen away from the direct pathways of assimilation. The liberated ammonia is re-assimilated, but up to 25% of the carbon may be released into the atmosphere as CO₂. Because of the loss of CO₂ and high energy costs, there has been considerable interest in attempts to decrease the flux through the cycle in C₃ plants. Transgenic tobacco plants were generated that contained the genes gcl and hyi from E. coli encoding glyoxylate carboligase (EC 4.1.1.47) and hydroxypyruvate isomerase (EC 5.3.1.22) respectively, targeted to the peroxisomes. It was presumed that the two enzymes could work together and compete with the aminotransferases that convert glyoxylate to glycine, thus avoiding ammonia production in the photorespiratory nitrogen cycle.

Results

When grown in ambient air, but not in elevated CO₂, the transgenic tobacco lines had a distinctive phenotype of necrotic lesions on the leaves. Three of the six lines chosen for a detailed study contained single copies of the gcl gene, two contained single copies of both the gcl and hyi genes and one line contained multiple copies of both gcl and hyi genes. The gcl protein was detected in the five transgenic lines containing single copies of the gcl gene but hyi protein was not detected in any of the transgenic lines. The content of soluble amino acids including glycine and serine, was generally increased in the transgenic lines growing in air, when compared to the wild type. The content of soluble sugars, glucose, fructose and sucrose in the shoot was decreased in transgenic lines growing in air, consistent with decreased carbon assimilation.

Conclusions

Tobacco plants have been generated that produce bacterial glyoxylate carboligase but not hydroxypyruvate isomerase. The transgenic plants exhibit a stress response when exposed to air, suggesting that some glyoxylate is diverted away from conversion to glycine in a deleterious short-circuit of the photorespiratory nitrogen cycle. This diversion in metabolism gave rise to increased concentrations of amino acids, in particular glutamine and asparagine in the leaves and a decrease of soluble sugars.