Braulio Medina

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Ynt1 is the only high-affinity nitrate uptake system in Hansenula polymorpha. Nitrate uptake was directly correlated with the Ynt1 levels and shown to be independent of nitrate reductase (NR) activity levels. Ynt1 failed to transport chlorate and, as a result, strains lacking YNT1 were sensitive to chlorate, as is the wild-type. Nitrite uptake in a(More)
Atropa baetica hairy roots, over-expressing cDNA from Hyoscyamus niger encoding the gene for hyoscyamine 6β-hydroxylase (H6H), were produced by Agrobacterium rhizogenes infection. The transgenic roots over-expressing h6h had an altered alkaloid profile in which hyoscyamine was entirely converted into scopolamine. In the best h6h clone, scopolamine(More)
An integrative expression vector based on promoter and terminator transcriptional sequences from the Hansenula polymorpha nitrate reductase gene (YNR1) has been developed to express nitrate assimilation plant genes in the nitrate assimilatory yeast H. polymorpha. Using this vector a plant nitrate reductase cDNA (tobacco Nia2) was expressed for the first(More)
The role of nitrate reductase (NR) in the regulation of the nitrate assimilation pathway was evaluated in the yeast Hansenula polymorpha. Posttranscriptional regulation of NR in response to reduced nitrogen sources and the effect of a heterologous NR on the transcriptional regulation of nitrate-assimilatory gene expression was examined. The strain bearing(More)
Disruption of HpURE2 resulted in a low expression of genes encoding nitrate-assimilatory proteins; sensitivity to Li(+), Na(+), and Cd(2+); no induction of ENA1; low levels of the GATA-type transcription factor Gat1; and low intracellular Ca(2+) levels. Gat1 levels were also very low in a Δcnb1 mutant lacking the regulatory subunit of calcineurin. The(More)
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