Differences between nitrogen-tolerant and nitrogen-susceptible sweetpotato cultivars in photosynthate distribution and transport under different nitrogen conditions

ABSTRACT The movement of ammonium across biological membranes is mediated in both prokaryotes and eukaryotes by ammonium transport proteins (AMT/MEP) that constitute a family of related sequences. We have previously identified two ammonium permeases in Aspergillus nidulans, encoded by the meaA and mepA genes. Here we show that meaA is expressed in the presence of ammonium, consistent with the function of MeaA as the main ammonium transporter required for optimal growth on ammonium as a nitrogen source. In contrast, mepA, which encodes a high-affinity ammonium permease, is expressed only under nitrogen-limiting or starvation conditions. We have identified two additional AMT/MEP-like genes in A. nidulans, namely, mepB, which encodes a second high-affinity ammonium transporter expressed only in response to complete nitrogen starvation, and mepC, which is expressed at low levels under all nitrogen conditions. The MepC gene product is more divergent than the other A. nidulans AMT/MEP proteins and is not thought to significantly contribute to ammonium uptake under normal conditions. Remarkably, the expression of each AMT/MEP gene under all nitrogen conditions is regulated by the global nitrogen regulatory GATA factor AreA. Therefore, AreA is also active under nitrogen-sufficient conditions, along with its established role as a transcriptional activator in response to nitrogen limitation.

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Toxicity of titanium dioxide nanoparticles to Chlorella vulgaris Beyerinck (Beijerinck) 1890 (Trebouxiophyceae, Chlorophyta) under changing nitrogen conditions

Aquatic Toxicology ◽

10.1016/j.aquatox.2017.03.020 ◽

2017 ◽

Vol 187 ◽

pp. 108-114 ◽

Cited By ~ 20

Author(s):

Suleiman Dauda ◽

Mathias Ahii Chia ◽

Sunday Paul Bako

Keyword(s):

Titanium Dioxide ◽

Chlorella Vulgaris ◽

Titanium Dioxide Nanoparticles ◽

Nitrogen Conditions

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Hap2-3-5-Gln3 determine transcriptional activation of GDH1 and ASN1 under repressive nitrogen conditions in the yeast Saccharomyces cerevisiae

Microbiology ◽

10.1099/mic.0.044974-0 ◽

2011 ◽

Vol 157 (3) ◽

pp. 879-889 ◽

Cited By ~ 11

Author(s):

Hugo Hernández ◽

Cristina Aranda ◽

Geovani López ◽

Lina Riego ◽

Alicia González

Keyword(s):

Dna Binding ◽

Transcriptional Activation ◽

Specific Binding ◽

Transcriptional Response ◽

Transcriptional Regulator ◽

Transcriptional Responses ◽

Yeast Saccharomyces Cerevisiae ◽

Activation Domains ◽

Transcriptional Complex ◽

Nitrogen Conditions

The transcriptional activation response relies on a repertoire of transcriptional activators, which decipher regulatory information through their specific binding to cognate sequences, and their capacity to selectively recruit the components that constitute a given transcriptional complex. We have addressed the possibility of achieving novel transcriptional responses by the construction of a new transcriptional regulator – the Hap2-3-5-Gln3 hybrid modulator – harbouring the HAP complex polypeptides that constitute the DNA-binding domain (Hap2-3-5) and the Gln3 activation domain, which usually act in an uncombined fashion. The results presented in this paper show that transcriptional activation of GDH1 and ASN1 under repressive nitrogen conditions is achieved through the action of the novel Hap2-3-5-Gln3 transcriptional regulator. We propose that the combination of the Hap DNA-binding and Gln3 activation domains results in a hybrid modulator that elicits a novel transcriptional response not evoked when these modulators act independently.

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Does Elevated CO2 Affect the Physiology and Growth of Quercus Mongolica under Different Nitrogen Conditions?

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.277-279.528 ◽

2005 ◽

Vol 277-279 ◽

pp. 528-535

Author(s):

Oh Hyun Kyung ◽

Yeonsook Choung

Keyword(s):

Water Use Efficiency ◽

Elevated Co2 ◽

Water Use ◽

Physiological Activity ◽

Photosynthesis Rate ◽

Total Biomass ◽

High Nitrogen ◽

Quercus Mongolica ◽

Use Efficiency ◽

Nitrogen Conditions

The response of Quercus mongolica, one of the major tree species in Northeast Asia and the most dominant deciduous tree in Korea, was studied in relation to elevated CO2 and the addition of nitrogen to soil in terms of its physiology and growth over two years. Plants were grown from seed at two CO2 conditions (ambient and 700 µL L-1) and with two levels of soil nitrogen supply (1.5 mM and 6.5 mM). Elevated CO2 was found to significantly enhance the photosynthesis rate and water use efficiency by 2.3-2.7 times and by 1.3-1.8 times, respectively. Over time within a growing season, there was a decreasing trend in the photosynthesis rate. However, the decrease was slower especially in two-year-old seedlings grown in elevated CO2 and high nitrogen conditions, suggesting that their physiological activity lasted relatively longer. Improved photosynthesis and water use efficiency as well as prolonged physiological activity under high CO2 condition resulted in an increase in biomass accumulation. That is, in elevated CO2, total biomass increased by 1.7 and 1.2 times, respectively, for one- and two-year-old seedlings with low nitrogen conditions, and by 1.8 and 2.6 times with high nitrogen conditions. This result indicates that the effect of CO2 on biomass is more marked in high nitrogen conditions. This, therefore, shows that the effect of CO2 is accelerated by the addition of nitrogen. With the increase in total biomass, the number of leaves and stem diameter increased significantly, and more biomass was allocated in roots, resulting in structural change. Overall, the elevated CO2 markedly stimulated the physiology and growth of Q. mongolica. This demonstrates that Q. mongolica is capable of exploiting an elevated CO2 environment. Therefore, it will remain a dominant species and continue to be a major CO2 sink in the future, even though other resources such as nitrogen can modify the CO2 effect.

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