Potential for biocontrol of the exotic starfish<Emphasis Type="Italic">, Asterias amurensis</Emphasis>, using a native starfish

Asterias amurensis is a starfish native to the northern Pacific that was introduced into southern Australia in the 1980s. It is widely viewed as one of Australia’s most serious invasive marine pests, but there are few methods available to control new or established populations. The role of Coscinasterias muricata in controlling the distribution of Asterias in Port Phillip Bay, and its potential to eliminate new infestations of Asterias were investigated. Laboratory feeding trials, where alternative mussel prey were available, showed Coscinasterias consumed Asterias at the rate of ~45/year. Field surveys in Port Phillip Bay showed that most Coscinasterias occurred at depths shallower than 15 m, while most Asterias occurred at depths greater than 15 m, and the ratio of Asterias/Coscinasterias only exceeded 45 at depths greater than 15 m. Consequently, if laboratory and field feeding rates are similar, Coscinasterias would be expected to exert significant control over Asterias populations at depths shallower than 15 m, and augmenting Coscinasterias populations at sites of new Asterias infestations may help eliminate newly-established populations.     

Non-target effects of transgenic blight-resistant American chestnut (Fagales: Fagaceae) on insect herbivores

American chestnut [Castanea dentata (Marshall) Borkhausen], a canopy dominant species across wide swaths of eastern North America, was reduced to an understory shrub after introduction of the blight fungus [Cryphonectria parasitica (Murrill) Barr] in the early 1900s. Restoration of American chestnut by using biotechnology is promising, but the imprecise nature of transgenesis may inadvertently alter tree phenotype, thus potentially impacting ecologically dependent organisms. We quantified effects of genetic engineering and fungal inoculation of trees on insect herbivores by using transgenic American chestnuts expressing an oxalate oxidase gene and wild-type American and Chinese (C. mollissima Blume) chestnuts. Of three generalist folivores bioassayed, only gypsy moth [Lymantria dispar (L.)] was affected by genetic modification, exhibiting faster growth on transgenic than on wild-type chestnuts, whereas growth of polyphemus moth [Antheraea polyphemus (Cramer)] differed between wild-type species, and fall webworm [Hyphantria cunea (Drury)] performed equally on all trees. Inoculation of chestnuts with blight fungus had no effect on the growth of two herbivores assayed (polyphemus moth and fall webworm). Enhanced fitness of gypsy moth on genetically modified trees may hinder restoration efforts if this invasive herbivore's growth is improved because of transgene expression.     

Raising yield potential of wheat. II. Increasing photosynthetic capacity and efficiency

Past increases in yield potential of wheat have largely resulted from improvements in harvest index rather than increased biomass. Further large increases in harvest index are unlikely, but an opportunity exists for increasing productive biomass and harvestable grain. Photosynthetic capacity and efficiency are bottlenecks to raising productivity and there is strong evidence that increasing photosynthesis will increase crop yields provided that other constraints do not become limiting. Even small increases in the rate of net photosynthesis can translate into large increases in biomass and hence yield, since carbon assimilation is integrated over the entire growing season and crop canopy. This review discusses the strategies to increase photosynthesis that are being proposed by the wheat yield consortium in order to increase wheat yields. These include: selection for photosynthetic capacity and efficiency, increasing ear photosynthesis, optimizing canopy photosynthesis, introducing chloroplast CO(2) pumps, increasing RuBP regeneration, improving the thermal stability of Rubisco activase, and replacing wheat Rubisco with that from other species with different kinetic properties.     

Bioenergy Plants: Hopes,Concerns and Prospectives

There are major concerns over both the security of energy supplies (declining supplies and political control) and the environmental costs associated with energy generation and use.The global consumption of carbon-containing fossil fuels for     

An Integrated Approach to Crop Genetic Improvement

The balance between the supply and demand of the major food crops is fragile,fueling concerns for long-term global food security.The rising population,increasing wealth and a proliferation of nonfood uses(e.g.bioenergy) has led to growing demands on agriculture,while increased production is limited by greater urbanization,and the degradation of land.Furthermore,global climate change with increasing temperatures and lower,more erratic rainfall is projected to decrease agricultural yields.There is a predicted need to increase food production by at least 70% by 2050 and therefore an urgent need to develop novel and integrated approaches,incorporating high-throughput phenotyping that will both increaseproduction per unit area and simultaneously improve the resource use efficiency of crops.Yield potential,yield stability,nutrient and water use are all complex multigenic traits and while there is genetic variability,their complexity makes such traits difficult to breed for directly.Nevertheless molecular plant breeding has the potential to deliver substantial improvements,once the component traits and the genes underlying these traits have been identified.In addition,interactions between the individual traits must also be taken into account,a demand that is difficult to fulfill with traditional screening approaches.Identified traits will be incorporated into new cultivars using conventional or biotechnological tools.In order to better understand the relationship between genotype,component traits,and environment over time,a multidisciplinary approach must be adopted to both understand the underlying processes and identify candidate genes,QTLs and traits that can be used to develop improved crops.     

Regulation of aspartate-derived amino-acid metabolism in Zygosaccharomyces rouxii compared to Saccharomyces cerevisiae

To elucidate the growth inhibitory effect of threonine, the regulation of the aspartate-derived amino-acid metabolism in Zygosaccharomyces rouxii, an important yeast for the flavor development in soy sauce, was investigated. It was shown that threonine inhibited the growth of Z. rouxii by blocking the methionine synthesis. It seemed that threonine blocked this synthesis by inhibiting the conversion of aspartate. In addition, it was shown that the growth of Z. rouxii, unlike that of Saccharomyces cerevisiae, was not inhibited by the herbicide sulfometuron methyl (SMM). From enzyme assays, it was concluded that the acetohydroxy acid synthase in Z. rouxii, unlike that in S. cerevisiae, was not sensitive to SMM. Furthermore, the enzyme assays demonstrated that the activity of threonine deaminase in Z. rouxii, like in S. cerevisiae, was strongly inhibited by isoleucine and stimulated by valine. From this work, it is clear that the aspartate-derived amino-acid metabolism in Z. rouxii only partly resembles that in S. cerevisiae.     

Determination of glutamic acid decarboxylase 65 peptides presented by the type I diabetes-associated HLA-DQ8 class II molecule identifies an immunogenic peptide motif

Particular HLA class II allelic sequences are associated with susceptibility to type I diabetes. To understand the mechanism, knowledge of the molecular nature of the specific TCR/peptide/class II interactions involved in the disease process is required. To this end, we have introduced the diabetes-associated human class II HLA-DQ8 allele (DQA1*0301/DQB1*0302) as a transgene into mice and analyzed T cell responses restricted by this molecule to an important Ag in human diabetes, human glutamic acid decarboxylase 65. Hybridomas were used to determine the particular peptides from this Ag presented by HLA-DQ8 to T cells and to map the core minimal epitopes required for T cell stimulation. Analysis of these core epitopes reveals a motif and relevant features for peptides that are immunogenic to T cells when presented by HLA-DQ8. The major immunogenic epitopes of glutamic acid decarboxylase 65 do not contain a negatively charged residue that binds in the P9 pocket of the HLA-DQ8 molecule. PBMC from HLA-DQ8+ diabetic and nondiabetic individuals respond to these peptides, confirming that the mouse model is a useful tool to define epitopes of autoantigens that are processed by human APC and recognized by human T cells.     

Effects of water hardness and alkalinity on the toxicity of uranium to a tropical freshwater hydra (Hydra viridissima)

In tropical Australian freshwaters, uranium (U) is of potential ecotoxicological concern, largely as a consequence of mining activities. Although the toxicity of uranium to Australian freshwater biota is comprehensive, by world standards, few data are available on the effects of physicochemical variables, such as hardness, alkalinity, pH and organic matter, on uranium speciation and bioavailability. This study determined the individual effects of water hardness (6.6, 165 and 330 mg l^-1 as CaCO₃) and alkalinity (4.0 and 102 mg l^-1 as CaCO₃), at a constant pH (6.0), on the toxicity (96 h population growth) of uranium to Hydra viridissima (green hydra). A 50-fold increase in hardness (Ca and Mg concentration) resulted in a 92% (two-fold) decrease in the toxicity of uranium to H. viridissima [i.e . an increase in the EC₅₀ value and 95% confidence interval from 114 (107-121) to 219 (192-246) µg l^-1]. Conversely, at a constant hardness (165 mg l-1 as CaCO₃), the toxicity of uranium to H. viridissima was not significantly (P > 0.05) affected by a 25-fold increase in alkalinity (carbonate concentration) [i.e. EC₅₀ values of 177 (166-188) and 171 (150-192) µg l^-1 at 4.0 and 102 mg l^-1 as CaCO₃, respectively]. A knowledge of the relationship between water chemistry variables, including hardness and alkalinity, and uranium toxicity is useful for predicting the potential ecological detriment in aquatic systems, and can be used to relax national water quality guidelines on a site-specific basis.