Over-expression of a tomato N-acetyl-L-glutamate synthase gene (SlNAGS1) in Arabidopsis thaliana results in high ornithine levels and increased tolerance in salt and drought stresses

A single copy of the N-acetyl-L-glutamate synthase gene (SlNAGS1) has been isolated from tomato. The deduced amino acid sequence consists of 604 amino acids and shows a high level of similarity to the predicted Arabidopsis NAGS1 and NAGS2 proteins. Furthermore, the N-terminus ArgB domain and the C-terminus ArgA domain found in SlNAGS1 are similar to the structural arrangements that have been reported for other predicted NAGS proteins. SlNAGS1 was expressed at high levels in all aerial organs, and at basic levels in seeds, whereas it was not detected at all in roots. SlNAGS1 transcript accumulation was noticed transiently in tomato fruit at the red-fruit stage. In addition, an increase of SlNAGS1 transcripts was detected in mature green tomato fruit within the first hour of exposure to low oxygen concentrations. Transgenic Arabidopsis plants have been generated expressing the SlNAGS1 gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter. Three homozygous transgenic lines expressing the transgene (lines 1-7, 3-8, and 6-5) were evaluated further. All three transgenic lines showed a significant accumulation of ornithine in the leaves with line 3-8 exhibiting the highest concentration. The same lines demonstrated higher germination ability compared to wild-type (WT) plants when subjected to 250 mM NaCl. Similarly, mature plants of all three transgenic lines displayed a higher tolerance to salt and drought stress compared to WT plants. Under most experimental conditions, transgenic line 3-8 performed best, while the responses obtained from lines 1-7 and 6-5 depended on the applied stimulus. To our knowledge, this is the first plant NAGS gene to be isolated, characterized, and genetically modified

High Resolution Melting (HRM) analysis on <em>VviDXS</em> to reveal muscats or non-muscats among autochthonous Greek wine producing grape varieties

Muscat flavor in grapes is associated with a substitution of a Single Nucleotide Polymorphism (SNP) located at position 1822 (SNP1822G>T) within the coding sequence of the VviDXS gene. Various methods, including the use of High Resolution Melting (HRM) analysis, have been suggested to discriminate different SNP allelic states including the molecular discrimination of the muscat from the non-muscat grape varieties, thus providing the ability to minimize lengthy grape breeding programs when selecting for grape muscat flavor before the fruit maturity stage. HRM analysis on the SNP1822 was performed on a group of 128 wine producing grape varieties in order to separate the muscat from the non-muscat genotypes before they are used for further breeding activities. This approach could be used either as a single-step prescreening method or in accordance with recently published methodology to elucidate on varietal characterization and authentication as these are important requirements concerning nurseries, growers and winemakers

Journal of Experimental Botany, Page 1 of 13

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