Fluoride metabolism in Acacia georginae Gidyea

1. The metabolism of fluoride in seedlings and small plants of Acacia georginae has been studied with the idea of finding the conditions under which the plant makes fluoroacetate in the laboratory. 2. Individual seedlings vary in the extent to which they take up fluoride and convert it into a form other than inorganic which is here called `organic' fluoride, F(org.). The differences between the toxicity of A. georginae Gidyea trees may therefore be genetic in origin. 3. The uptake of fluoride from solutions 0·525–1·05mm (10–20p.p.m.) was not large. In 1–4 days it reached 8 p.p.m. in the aerial parts and 16 p.p.m. in the roots. Unlike the distribution of the halogen in grass, total fluoride was greater than inorganic fluoride. It was almost a rule that more `organic' fluoride was present in the roots than in the aerial parts. 4. With higher concentrations of fluoride 10·5–15·75mm (200–300p.p.m.) much larger amounts of fluoride were taken up, especially by the roots, and much more apparent organic fluoride was formed. 5. pH had a large influence upon the intake, this being lowest at an initial pH8·4 and highest at pH4·0. The pH outside this range was not investigated.     

Influence of galls of Phanacis taraxaci on carbon partitioning within common dandelion, Taraxacum officinale

We examined how leaf galls, induced by the cynipid wasp Phanacis taraxaci, influence the partitioning of photoassimilates within the host, the common dandelion, Taraxacum officinale. Galled and ungalled plants were exposed to ¹⁴CO₂ and the labelled photoassimilates accumulating within galls and other parts of the host were measured. During the growth phase of the gall they were physiological sinks for photoassimilates, accumulating 9% to 70% of total carbon produced by the host, depending upon the number of galls per plant. High levels of ¹⁴C assimilation in the leaves of galled plants compared to controls, suggest that galls actively redirect carbon resources from unattacked leaves of their host plant. This represents a significant drain on the carbon resources of the host, which increases with the number and size of galls per plant. Active assimilation of ¹⁴C by the gall is greatest in the growth phase and is several orders of magnitude lower in the maturation phase. This finding is consistent with physiological and anatomical changes that occur during the two phases of gall development and represents a key developmental strategy by cynipids to ensure adequate food resources before larval growth begins.     

Gall Formation on Cirsium arvense by Ditylenchus dipsaci

Ditylenchus dipsaci was found to cause gall formation on the stems of Cirsium arvense. The galls were characterized by extensive hypertrophy and hyperplasia, differentiation of nutritive tissue, nuclear modification, and a central cavity containing nematodes. These findings emphasize the importance of host response in investigations of host-parasite interactions and suggest that D. dipsaci may be evolving a host race by reproductive isolation within the confines of a plant gall.     

Cancer-causing BRCA2 missense mutations disrupt an intracellular protein assembly mechanism to disable genome maintenance

Cancer-causing missense mutations in the 3418 amino acid BRCA2 breast and ovarian cancer suppressor protein frequently affect a short (∼340 residue) segment in its carboxyl-terminal domain (DBD). Here, we identify a shared molecular mechanism underlying their pathogenicity. Pathogenic BRCA2 missense mutations cluster in the DBD’s helical domain (HD) and OB1-fold motifs, which engage the partner protein DSS1. Pathogenic - but not benign – DBD mutations weaken or abolish DSS1-BRCA2 assembly, provoking mutant BRCA2 oligomers that are excluded from the cell nucleus, and disable DNA repair by homologous DNA recombination (HDR). DSS1 inhibits the intracellular oligomerization of wildtype, but not mutant, forms of BRCA2. Remarkably, DSS1 expression corrects defective HDR in cells bearing pathogenic BRCA2 missense mutants with weakened, but not absent, DSS1 binding. Our findings identify a DSS1-mediated intracellular protein assembly mechanism that is disrupted by cancer-causing BRCA2 missense mutations, and suggest an approach for its therapeutic correction.     

The effects of light and noise from urban development on biodiversity: Implications for protected areas in Australia

Global population growth and associated urban development are having profound effects on biodiversity. Two major outcomes of expanding development that affect wildlife are light and noise pollution. In this paper, we review literature reporting the effects of light and noise on biodiversity, and assess implications for conservation planning in Australia. Our results clearly indicate that light and noise pollution have the potential to affect the physiology, behaviour and reproduction of a range of animal taxa. Types of effects include changes in foraging and reproductive behaviours, reduction in animal fitness, increased risk of predation and reduced reproductive success. These could have flow‐on consequences at the population and ecosystem levels. We found a significant gap in knowledge of the impact of these pollutants on Australian fauna. To reduce the effect of light and noise pollution, there needs to be careful planning of urban areas in relation to protected areas, and for biodiversity more generally. Potential measures include strategically planning the types of development and associated human activities adjacent to protected areas, and the use of shields and barriers, such as covers for lights or the use of dense native vegetation screens, while still allowing movement of animals. Changes in government standards and regulations could also help to reduce the impacts of light and noise pollution.     

Deleterious effects of mild simulated overwintering temperatures on survival and potential fecundity of rose-galling Diplolepis wasps (Hymenoptera: Cynipidae)

Prepupae of the rose galling Diplolepis spinosa from areas with relatively cold winters in southern Canada, and Diplolepis variabilis from a milder locale in western Canada, were used to test the hypothesis that mild winter temperatures are detrimental to the survival and potential fecundity of insects. Prepupae of D. spinosa held within or removed from their galls were exposed to simulated overwintering temperatures (-22, 0, 5, or 10 degrees C) for approximately four months before measuring their survival, body size, and potential fecundity. Similar studies were conducted using prepupae of D. variabilis that were removed from their gall and subjected to 0 degrees C or 10 degrees C treatments. Diplolepis spinosa, with or without their galls, averaged 66% more mortality at 10 degrees C than at 0 degrees C. Female D. spinosa that survived the 10 degrees C treatment had 32% fewer eggs than those held at 0 degrees C. In contrast, there was no difference in survival or numbers of eggs between D. variabilis held at 0 degrees C and 10 degrees C. Body size of adult females and size of eggs did not differ among temperature treatments for either species. We conclude that mild overwintering temperatures may be detrimental for insects by raising their metabolism, and consequently reducing energetic reserves needed for development to the adult stage and subsequent production of eggs the following spring.     

Horse riding in urban conservation areas: Reviewing scientific evidence to guide management

Summary We undertook a literature review of the impacts of horse riding in conservation areas, and used it to guide management of horse riding in Canberra Nature Park (CNP), a large, fragmented semi‐natural park in and around the city of Canberra in the Australian Capital Territory. The literature review established that, because of their relatively large weight and small area in contact with the ground, horses have a relatively high potential for doing environmental damage. Impacts tend to be generally lowest for hikers, followed by motorcycles, horses and four‐wheeled vehicles. One study showed horse traffic caused more damage on established trails than motorcycles, off‐road bicycles or hikers. Most published studies of horse‐riding impacts in Australia have been conducted in alpine and subalpine environments, and in temperate woodlands and forests on sandstone near Sydney. They have shown that impacts are generally highest in previously untracked areas. Impacts on established trails are generally most marked on sections of trail that are wet, boggy or steep, and on unplanned and unmaintained trails. Impacts are lowest on constructed and maintained trails. Trail proliferation, associated with avoidance of untrafficable sections and short‐cutting, can be a major problem. Horses also have potential to spread weeds, because pastures and dried stock feeds contain large numbers of weed seeds that retain high levels of viability in horse manure. The risk of weed establishment is highest when manure is deposited in disturbed, damp sites, particularly when riding off‐track. Much less weed establishment is apparent when horse riders remain on‐track. Horse riding is a popular activity, but one that is relatively expensive to provide for, and one that may reduce opportunities for lower‐impact recreational park users. For all these reasons it appears socially equitable that provision is made for lower numbers of horse riders compared to numbers of park users involved in lower impact, more passive, recreational activities. We conclude by describing how this information was used to develop principles to guide management of horse riding and assess risk at individual sites in Canberra Nature Park.     

Properties of cytotoxic peptide-formed ion channels

Cytotoxic peptides are relatively small cationicmolecules such as those found 1) in venoms, e.g., melittin inbee, scorpion toxins in scorpion, pilosulin 1 in jumper ant, andlycotoxin I and II in wolf spider; 2) in skin secretions (e.g.,magainin I and II from Xenopus laevis, dermaseptin from frog,antimicrobials from carp) and cells of the immune system (e.g., insect,scorpion, and mammalian defensins and cryptdins); 3) asautocytotoxicity peptides, e.g., amylin cytotoxic to pancreatic-cells, prion peptide fragment 106-126[PrP-(106-126)], and amyloid -protein (AP)cytotoxic to neurons; and 4) as designed synthetic peptides based on the sequences and properties of naturally occurring cytotoxic peptides. The small cytotoxic peptides are composed of -sheets, e.g., mammalian defensins, AP, amylin, and PrP-(106-126),whereas the larger cytotoxic peptides have several domains composed of both -helices and -sheets stabilized by cysteine bonds, e.g., scorpion toxins, scorpion, and insect defensins. Electrophysiological and molecular biology techniques indicate that these structures modifycell membranes via 1) interaction with intrinsic ion transport proteins and/or 2) formation of ion channels. These twononexclusive mechanisms of action lead to changes in second messengersystems that further augment the abnormal electrical activity anddistortion of the signal transduction causing cell death.

     

Evidence for long-distance, chemical gall induction by an insect

Abstract We report that a chemical stimulus from a herbivore, a galling insect, changes plant morphology and physiology to benefit the herbivore. Previous studies could not determine whether insect galls are induced by mechanical or chemical stimuli because feeding and oviposition both occurred at the site of gall formation. We report that the mouthparts of a spruce‐galling insect, Adelges cooleyi, were inserted in stem phloem cells far from induced galls, that tissues between mouthparts and galls appeared normal, and that the ability to initiate galls was inversely correlated with distance from buds (potential gall sites). Thus the effects of chemical stimuli were unambiguously separated from any mechanical influence of probing stylets or ovipositors. Our results strongly suggest that galls were induced by a chemical stimulus transported to buds via vascular tissue and that its efficacy was dose‐dependent.