Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P39060 (endostatin)
 2,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A de-repression mechanism based on the disappearance of 'signals' down-regulating N transporter activity has been proposed in the literature to explain the transient increase of NO(3)(-) uptake by the roots following N deprivation in higher plants. This hypothesis was investigated at the physiological and molecular levels by measuring NO(3)(-) influx into roots of Brassica napus L. grown under low or high external concentrations of KNO(3) following N deprivation. Parallel measurements were made of endogenous NO(3)(-), amino acid concentrations and abundance of mRNA for BnNRT1 and BnNRT2, genes encoding nitrate-inducible transport proteins. The effect of NO(3)(-) pulsing on NO(3)(-) transport components in N-deprived plants was also investigated by measuring influx of high- and low-affinity transport system (HATS and LATS) and assaying mRNA levels. Influx of NO(3)(-) via HATS and LATS, and transcript levels of BnNRT2 and BnNRT1 decreased with the duration of N deprivation. The results suggested that the absence of de-repression of NO(3)(-) influx and BnNRT2 gene expression following N starvation was related to a high amino acid status. Pulsing with NO(3)(-) induced a large increase in BnNRT2 mRNA level, but a comparatively small increase in NO(3)(-) influx via HATS. The level of BnNRT1 mRNA also increased, but there was no effect on LATS uptake activity. The absence of a strict correlation between the NO(3)(-) transport activity and the mRNA BnNRT1 and BnNRT2 levels is discussed in terms of possible post-transcriptional regulation by the amino acids.
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PMID:Effects of nitrate pulses on BnNRT1 and BnNRT2 genes: mRNA levels and nitrate influx rates in relation to the duration of N deprivation in Brassica napus L. 1214 21

Transmembrane electrical potential differences (Deltapsi) of epidermal and cortical cells were measured in intact roots of barley (Hordeum vulgare L. cv Klondike). The effects of exogenous NO(3) (-) on Deltapsi (in the concentration range from 100 micromolar to 20 millimolar) were investigated to probe the mechanisms of nitrate uptake by the high-affinity (HATS) and low-affinity (LATS) transport systems for NO(3) (-) uptake. Both transport systems caused depolarization of Deltapsi, demonstrating that the LATS (like the HATS) for NO(3) (-) uptake is probably mediated by an electrogenic cation (H(+)?) cotransport system. Membrane depolarization by the HATS was "inducible" by NO(3) (-), and saturable with respect to exogenous [NO(3) (-)]. By contrast, depolarization by the LATS was constitutive, and first-order in response to external [NO(3) (-)]. H(+) fluxes, measured in 200 micromolar and in 5 millimolar Ca(NO(3))(2) solutions, failed to alkalinize external media as anticipated for a 2 H(+):1 NO(3) (-) symport. However, switching from K(2)SO(4) solutions (which were strongly acidifying) to KNO(3) solutions at the same K(+) concentration caused marked reductions in H(+) efflux. These observations are consistent with NO(3) (-) uptake by the HATS and the LATS via 2 H(+):1 NO(3) (-) symports. These observations establish that the HATS for nitrate uptake by barley roots is essentially similar to those reported for Lemna and Zea mays by earlier workers. There are, nevertheless, distinct differences between barley and corn in their quantitative responses to external NO(3) (-).
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PMID:Studies of the Uptake of Nitrate in Barley : IV. Electrophysiology. 1666 7