Biomedical subjects

Meriel G Jones

Publications and source records attributed to Meriel G Jones.

5 recordsLinked to original sources

PubMed2007

The first filamentous fungal genome sequences: Aspergillus leads the way for essential everyday resources or dusty museum specimens?

The published Aspergillus genome sequences (A. nidulans, A. fumigatus, A. oryzae) and further sequence data from A. clavatus, Neosartorya fischeri, A. flavus, A. niger, A. parasiticus and A. terreus are the first from a group of related filamentous fungi. They indicate the gains possible from genomic approaches, but also problems that arise after the sequences are finished. Benefits include a greater understanding of genome structure and evolution, insights into gene regulation, predictions of new factors that may be relevant to pathogenicity and the discovery of novel enzymes with biotechnological value. Areas where further developments are needed include gene and structure-function predictions, methods for comparative genome analysis and the interfaces for access to genome information. In addition, strategies for continued maintenance and updating need to be developed at the start of the post-genomic era to increase the value of genome sequences into the future.

Aspergillus↗

PubMed2006

Effect of low storage temperature on some of the flavour precursors in garlic (Allium sativum).

Garlic (Allium sativum) cloves were stored at ambient temperature and 4 degrees C for periods up to six months to establish the effect of position of the individual clove within the bulb and of low storage temperature on the composition of several flavours precursors and other organic sulphur compounds, measured by gradient High Pressure Liquid Chromatography. Levels of alliin, gamma glutamyl allyl cysteine sulphoxide and gamma glutamyl isoallyl cysteine sulphoxide were statistically significantly higher in outer than in inner cloves. There was no statistically significant change in levels of alliin, the major flavour precursor, in cloves stored at 4 degrees C, remaining in the average range 17.5+/-3.8-39.1+/-7.5 mM. However, isoalliin increased significantly during storage at 4 degrees C, rising from an average 0.6+/-0.2 mM (outer cloves) -- 0.7+/-0.4 mM (inner cloves) to 7.1+/-1.7 mM (outer cloves) -- 4.1+/-0.7 mM (inner cloves). A decline in other sulphur-containing compounds, most likely to be the peptides gamma-glutamyl allylcysteine sulphoxide and gamma-glutamyl isoallylcysteine sulphoxide, occurred at the same time and possibly contributed to the increase in the flavour precursor compounds. The degree of chemical changes during storage will be of interest to the food and pharmaceutical industries.

Chromatography, High Pressure Liquid↗

PubMed2006

Opposing signals differentially regulate transcript stability in Aspergillus nidulans.

A good model for gene regulation, requiring the organism to monitor a complex and changing environment and respond in a precise and rapid way, is nitrogen metabolism in Aspergillus nidulans. This involves co-ordinated expression of hundreds of genes, many dependent on the transcription factor AreA, which monitors the nitrogen state of the cell. AreA activity is in part modulated by differential degradation of its transcript in response to intracellular glutamine. Here we report that glutamine triggers synchronized degradation of a large subset of transcripts involved in nitrogen metabolism. Among these are all four genes involved in the assimilation of nitrate. Significantly, we show that two of these transcripts, niaD and niiA, are stabilized by intracellular nitrate, directly reinforcing transcriptional regulation. Glutamine-signalled degradation and the nitrate-dependent stabilization of the niaD transcript are effected at the level of deadenylation and are dependent on its 3' UTR. When glutamine and nitrate are both present, nitrate stabilization is predominant, ensuring that nitrate and the toxic intermediate nitrite are removed from the cell. Regulated transcript stability is therefore an integral part of the adaptive response. This represents the first example of distinct physiological signals competing to differentially regulate transcripts at the level of deadenylation.

3' Untranslated Regions↗

PubMed2005

Genetic analysis of the TOR pathway in Aspergillus nidulans.

We identified five genes encoding components of the TOR signaling pathway within Aspergillus nidulans. Unlike the situation in Saccharomyces cerevisiae, there is only a single Tor kinase, as in plant and animal systems, and mutant phenotypes suggest that the TOR pathway plays only a minor role in regulating nitrogen metabolism.

Amino Acid Sequence↗

PubMed2004

Biosynthesis of the flavour precursors of onion and garlic.

Onion (Allium cepa), garlic (A. sativum) and other Alliums are important because of the culinary value of their flavours and odours. These are characteristic of each species and are created by chemical transformation of a series of volatile sulphur compounds generated by cleavage of relatively stable, odourless, S-alk(en)yl cysteine sulphoxide flavour precursors by the enzymes alliinase and lachrymatory-factor synthase. These secondary metabolites are S-methyl cysteine sulphoxide (MCSO, methiin; present in most Alliums, some Brassicaceae), S-allyl cysteine sulphoxide (ACSO, alliin; characteristic of garlic), S-trans-prop-1-enyl cysteine sulphoxide (PECSO, isoalliin; characteristic of onion), and S-propyl cysteine sulphoxide (PCSO, propiin; in onion and related species). Information from studies of the transformation of putative biosynthetic intermediates, radiolabelling, and from measurements of sulphur compounds within onion and garlic have provided information to suggest a biosynthetic pathway. This may involve alk(en)ylation of the cysteine in glutathione, followed by cleavage and oxidation to form the alk(en)yl cysteine sulphoxide flavour precursors. There is also evidence that synthesis of the flavour precursors may involve (thio)alk(en)ylation of cysteine or a precursor such as O-acetyl serine. Both routes may occur depending on the physiological state of the tissue. There are indications from the effects of environmental factors, such as the availability of sulphur, that control of the biosynthesis of each flavour precursor may be different. Cysteine and glutathione metabolism are discussed to indicate parallels with Allium flavour precursor biosynthesis. Finally, possible avenues for exploration to determine the origin in planta of the alk(en)yl groups are suggested.

Cysteine↗