Storage products and transcriptional analysis of the endosperm of cultivated wheat and two wild wheat species.

The starch and protein in wheat (Triticum aestivum L.) endosperm provide 20 percent of the calories eaten by humans and were heavily selected for during domestication. We examined the main storage products and gene expression patterns that may embody compositional differences between two wild species Aegilops crassa and Aegilops tauschii and cultivated bread wheat. The storage product profiles differed significantly with T. aestivum accumulating twice as much carbon as the wild species, while the latter had 1.5 to 2-fold more total nitrogen per seed. Transcriptional analyses of endosperms of similar fresh weight were compared using a cDNA macroarray. Aegilops tauschii, and especially Ae. crassa had stronger hybridizations with storage protein sequences, but while there were differences in transcripts for starch biosynthetic genes, they were less dramatic. Of these, we cloned the Starch Branching Enzymes (SBE) IIa promoter region and the genomic clone of the Brittle-1 (Bt1) ADPglucose transporter. While Ae. crassa SBEIIa sequence was more divergent than that of Ae. tauschii's compared to bread wheat, there were no sequence polymorphisms that would explain the observed expression differences in Bt1 between these species. Furthermore, while there were nucleotide differences between Bt1 in Ae. crassa and bread wheat, they were synonymous at the amino acid level. Some of transcriptional differences identified here, however, deserve further examination as part of a strategy to manipulate wheat starch and protein composition.

ADP-glucose pyrophosphorylase is located in the plastid in developing tomato fruit.

The subcellular location of activity and protein of ADP-glucose pyrophosphorylase (AGPase) in developing tomato (Lycopersicon esculentum) fruit was determined following a report that the enzyme might be present inside and outside the plastids in this organ. Plastids prepared from crude homogenates of columella and pericarp, the starch-accumulating tissues of developing fruit, contained 8% to 18% of the total activity of enzymes known to be confined to plastids, and 0.2% to 0.5% of the total activity of enzymes known to be confined to the cytosol. The proportion of the total activity of AGPase in the plastids was the same as that of the enzymes known to be confined to the plastid. When samples of plastid and total homogenate fractions were subjected to immunoblotting with an antiserum raised to AGPase, most or all of the protein detected was plastidial. Taken as a whole, these data provide strong evidence that AGPase is confined to the plastids in developing tomato fruit.

A cytosolic ADP-glucose pyrophosphorylase is a feature of graminaceous endosperms, but not of other starch-storing organs.

The occurrence of an extra-plastidial isoform of ADP-glucose (Glc) pyrophosphorylase (AGPase) among starch-storing organs was investigated in two ways. First, the possibility that an extra-plastidial isoform arose during the domestication of cereals was studied by comparing the intracellular distribution of enzyme activity and protein in developing endosperm of noncultivated Hordeum species with that previously reported for cultivated barley (Hordeum vulgare). As in cultivated barley, the AGPase of H. vulgare subsp. spontaneum and Hordeum murinum endosperm is accounted for by a major extra-plastidial and a minor plastidial isoform. Second, the ratio of ADP-Glc to UDP-Glc was used as an indication of the intracellular location of the AGPase activity in a wide range of starch-synthesizing organs. The ratio is expected to be high in organs in which UDP-Glc and ADP-Glc are synthesized primarily in the cytosol, because the reactions catalyzed by AGPase and UDP-Glc pyrophosphorylase will be coupled and close to equilibrium. This study revealed that ADP-Glc contents and the ratio of ADP-Glc to UDP-Glc were higher in developing graminaceous endosperms than in any other starch-storing organs. Taken as a whole the results indicate that an extra-plastidial AGPase is important in ADP-Glc synthesis in graminaceous endosperms, but not in other starch-storing organs.

Utilization of bioremediation processes for the treatment of PAH-contaminated sediments.

The widespread contamination of aquatic sediments by polycyclic aromatic hydrocarbons (PAHs) has created a need for cost-effective remediation processes. Many common PAHs are biodegradable, leading to studies investigating the potential of sediment bioremediation. This article reviews several factors that currently complicate the implementation of sediment bioremediation processes: the effect of complex mixtures of contaminants on the rate and extent of degradation observed, the bioavailability of PAHs in sorbed- and nonaqueous-phase, and methods being evaluated to enhance degradation/availability (surfactant-enhanced solubility, nutrient addition, and bioaugmentation).

Contemporary seismicity of the Trinidad and Tobago region : Tectonic and earthquake hazard implications

Results are presented fron the first eleven years of operation of a radio-linked seismograph network in the Trinidad and Tobago region. All earthquakes of magnitude (mb) greater than about 2.8 have been relocated using the method of joint hypocentral determination (JHD). The results show an extremely complex pattern of seismicity and are presented as a set of maps showing earthquakes in different depth ranges. Important features of the earthquake distribution are that the supposed sontinuation of the El Pilar fault through the northern part of Trinidad has not been seismically active for at least the past decade and that there is a significant source of immediate-depth earthquakes to the east of Trinidad, the existence of which was previously unknowm. Our interpretation of the results favours oblique ongoing collision between the Lesser Antilles island arc and the South American continent rather than predominantly east-west strike slip motion.(AU)