Effects of harvesting callianassid (ghost) shrimps on subtropical benthic communities

The effects of harvesting of callianassid shrimp (Trypaea australiensis) on the abundance and composition of macrobenthic assemblages in unvegetated sediments of a subtropical coastal embayment in Queensland, Australia were examined using a combination of sampling and manipulative experiments. First, the abundance and composition of the benthic infauna in an area regularly used for the collection of shrimp for bait by recreational anglers was compared with multiple reference areas. Second, a BACI design, with multiple reference areas, was used to examine the short-term effects of harvesting on the benthic assemblages from an intensive commercialised fishing competition. Third, a large-scale, controlled manipulative experiment, where shrimp were harvested from 10,000 m² plots at intensities commensurate with those from recreational and commercial operators, was done to determine the impacts on different components of the infaunal assemblage.

Only a few benthic taxa showed significant declines in abundance in response to the removal of ghost shrimp from the unvegetated sediments. There was evidence, however, of more subtle effects with changes in the degree of spatial variation (patchiness) of several taxa as a result of harvesting. Groups such as capitellid polychaetes, gammarid amphipods and some bivalves were significantly more patchy in their distribution in areas subjected to harvesting than reference areas, at a scale of tens of metres. This scale corresponds to the patterns of movement and activity of recreational harvesters working in these areas. In contrast, patchiness in the abundance of ghost shrimp decreased significantly under harvesting at scales of hundreds of metres, in response to harvesters focussing their efforts on areas with greater numbers of burrow entrances, leading to a more even distribution of the animals. Controlled experimental harvesting caused declines in the abundance of soldier crabs (Mictyris longicarpus), polychaetes and amphipods and an increase in the spatial patchiness of polychaetes. Populations of ghost shrimp were, however, resilient to harvesting over extended periods of time. In conclusion, harvesting of ghost shrimp for bait by recreational and commercial fishers causes significant but localised impacts on a limited range of benthic fauna in unvegetated sediments, including changes in the degree of spatial patchiness in their distribution.     

A new PCR-based marker on chromosome 4AL for resistance to pre-harvest sprouting in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Pre-harvest sprouting (PHS) is a complex trait controlled by multiple genes with strong interaction between environment and genotype that makes it difficult to select breeding materials by phenotypic assessment. One of the most important genes for pre-harvest sprouting resistance is consistently identified on the long arm of chromosome 4A. The 4AL PHS tolerance gene has therefore been targeted by Australian white-grained wheat breeders. A new robust PCR marker for the PHS QTL on wheat chromosome 4AL based on candidate genes search was developed in this study. The new marker was mapped on 4AL deletion bin 13-0.59-0.66 using 4AL deletion lines derived from Chinese Spring. This marker is located on 4AL between molecular markers Xbarc170 and Xwg622 in the doubled-haploid wheat population Cranbrook × Halberd. It was mapped between molecular markers Xbarc170 and Xgwm269 that have been previously shown to be closely linked to grain dormancy in the doubled haploid wheat population SW95-50213 × Cunningham and was co-located with Xgwm269 in population Janz × AUS1408. This marker offers an additional efficient tool for marker-assisted selection of dormancy for white-grained wheat breeding. Comparative analysis indicated that the wheat chromosome 4AL QTL for seed dormancy and PHS resistance is homologous with the barley QTL on chromosome 5HL controlling seed dormancy and PHS resistance. This marker will facilitate identification of the gene associated with the 4A QTL that controls a major component of grain dormancy and PHS resistance.     

Body condition at weaning affects the duration of the postweaning fast in gray seal pups (Halichoerus grypus)

Gray seals (Halichoerus grypus) undergo a terrestrial postweaning fast (PWF) that depletes energy reserves acquired during the suckling interval. Plasticity in PWF duration may ensure that pups of variable body condition depart for sea with adequate energy reserves. To test this hypothesis, we examined body condition of 30 gray seal pups at weaning and monitored their PWF duration. On average, fat accounted for 47.3% +/- 0.7% of their 53.2 +/- 1.3-kg weaning mass. Although fasting duration averaged 21 +/- 1.1 d (n = p28), there was considerable variation in fasting duration (9 to > 31 d) and the resulting age when pups departed to sea (26 to > 49 d). Percent fat at weaning(38.6%-54.6%) was positively correlated with fasting duration(n = 28, r = 0.376, P = 0.0489). In contrast, total body gross energy (735.3-1,447.4 MJ) and body mass (39.0-66.0 kg) were not correlated with fasting duration. Thus, body composition,not overall body reserves, predicted fasting duration, but the effect was weak, indicating that other factors also account for the observed variation in fasting duration. We speculate that pups with greater percent fat more effectively utilized lipid and conserved protein while meeting metabolic costs throughout the PWF. As a result, fatter pups extended the PWF duration,which may be critical for development of diving physiology and may have facilitated their survivorship to age 1.     

Impaired ribosome biogenesis disrupts the integration between morphogenesis and nuclear duplication during the germination of Aspergillus fumigatus

Aspergillus fumigatus is an important opportunistic fungal pathogen that is responsible for high mortality rates in the immunosuppressed population. CgrA, the A. fumigatus ortholog of a Saccharomyces cerevisiae nucleolar protein involved in ribosome biogenesis, contributes to the virulence of this fungus by supporting rapid growth at 37 degrees C. To determine how CgrA affects ribosome biogenesis in A. fumigatus, polysome profile and ribosomal subunit analyses were performed on both wild-type A. fumigatus and a DeltacgrA mutant. The loss of CgrA was associated with a reduction in the level of 80S monosomes as well as an imbalance in the 60S:40S subunit ratio and the appearance of half-mer ribosomes. The gene expression profile in the DeltacgrA mutant revealed increased abundance of a subset of translational machinery mRNAs relative to the wild type, suggesting a potential compensatory response to CgrA deficiency. Although DeltacgrA conidia germinated normally at 22 degrees C, they swelled excessively when incubated at 37 degrees C and accumulated abnormally high numbers of nuclei. This hypernucleated phenotype could be replicated pharmacologically by germinating wild-type conidia under conditions of reductive stress. These findings indicate that the germination process is particularly vulnerable to global disruption of protein synthesis and suggest that CgrA is involved in both ribosome biogenesis and polarized cell growth in A. fumigatus.     

BACE-1 inhibitors part 3: identification of hydroxy ethylamines (HEAs) with nanomolar potency in cells

This article is focusing on further optimization of previously described hydroxy ethylamine (HEA) BACE-1 inhibitors obtained from a focused library with the support of X-ray crystallography. Optimization of the non-prime side of our inhibitors and introduction of a 6-membered sultam substituent binding to Asn-294 as well as a fluorine in the C-2 position led to derivatives with nanomolar potency in cell-based assays.     

Enhancer blocking and transvection at the Drosophila apterous locus

Intra- and interchromosomal interactions have been implicated in a number of genetic phenomena in diverse organisms, suggesting that the higher-order structural organization of chromosomes in the nucleus can have a profound impact on gene regulation. In Drosophila, homologous chromosomes remain paired in somatic tissues, allowing for trans interactions between genes and regulatory elements on the two homologs. One consequence of homolog pairing is the phenomenon of transvection, in which regulatory elements on one homolog can affect the expression of a gene in trans. We report a new instance of transvection at the Drosophila apterous (ap) locus. Two different insertions of boundary elements in the ap regulatory region were identified. The boundaries are inserted between the ap wing enhancer and the ap promoter and have highly penetrant wing defects typical of mutants in ap. When crossed to an ap promoter deletion, both boundary inserts exhibit the interallelic complementation characteristic of transvection. To confirm that transvection occurs at ap, we generated a deletion of the ap wing enhancer by FRT-mediated recombination. When the wing-enhancer deletion is crossed to the ap promoter deletion, strong transvection is observed. Interestingly, the two boundary elements, which are inserted ~10 kb apart, fail to block enhancer action when they are present in trans to one another. We demonstrate that this is unlikely to be due to insulator bypass. The transvection effects described here may provide insight into the role that boundary element pairing plays in enhancer blocking both in cis and in trans.     

Organoselenides from Nicotiana tabacum genetically modified to accumulate selenium

Nicotiana tabacum L. (tobacco) plants were transformed to overexpress a selenocysteine methyltransferase gene from the selenium hyperaccumulator Astragalus bisulcatus (Hook.) A. Gray (two-grooved milkvetch), and an ATP-sulfurylase gene from Brassica oleracea L. var. italica (broccoli). Solvent extraction of leaves harvested from plants treated with selenate revealed five selenium-containing compounds, of which four were identified by chemical synthesis as 2-(methylseleno)acetaldehyde, 2,2-bis(methylseleno)acetaldehyde, 4-(methylseleno)-(2E)-nonenal, and 4-(methylseleno)-(2E,6Z)-nonadienal. These four compounds have not previously been reported in nature.