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Julian I Schroeder - One of the best experts on this subject based on the ideXlab platform.

  • differential sodium and Potassium Transport selectivities of the rice oshkt2 1 and oshkt2 2 Transporters in plant cells
    Plant Physiology, 2010
    Co-Authors: Xuan Yao, Tomoaki Horie, Shaowu Xue, Ho Yin Leung, Maki Katsuhara, Dennis E Brodsky, Julian I Schroeder
    Abstract:

    Na+ and K+ homeostasis are crucial for plant growth and development. Two HKT Transporter/channel classes have been characterized that mediate either Na+ Transport or Na+ and K+ Transport when expressed in Xenopus laevis oocytes and yeast. However, the Na+/K+ selectivities of the K+-permeable HKT Transporters have not yet been studied in plant cells. One study expressing 5′ untranslated region-modified HKT constructs in yeast has questioned the relevance of cation selectivities found in heterologous systems for selectivity predictions in plant cells. Therefore, here we analyze two highly homologous rice (Oryza sativa) HKT Transporters in plant cells, OsHKT2;1 and OsHKT2;2, that show differential K+ permeabilities in heterologous systems. Upon stable expression in cultured tobacco (Nicotiana tabacum) Bright-Yellow 2 cells, OsHKT2;1 mediated Na+ uptake, but little Rb+ uptake, consistent with earlier studies and new findings presented here in oocytes. In contrast, OsHKT2;2 mediated Na+-K+ coTransport in plant cells such that extracellular K+ stimulated OsHKT2;2-mediated Na+ influx and vice versa. Furthermore, at millimolar Na+ concentrations, OsHKT2;2 mediated Na+ influx into plant cells without adding extracellular K+. This study shows that the Na+/K+ selectivities of these HKT Transporters in plant cells coincide closely with the selectivities in oocytes and yeast. In addition, the presence of external K+ and Ca2+ down-regulated OsHKT2;1-mediated Na+ influx in two plant systems, Bright-Yellow 2 cells and intact rice roots, and also in Xenopus oocytes. Moreover, OsHKT Transporter selectivities in plant cells are shown to depend on the imposed cationic conditions, supporting the model that HKT Transporters are multi-ion pores.

  • atkup1 an arabidopsis gene encoding high affinity Potassium Transport activity
    The Plant Cell, 1998
    Co-Authors: Eugene J Kim, June M Kwak, Nobuyuki Uozumi, Julian I Schroeder
    Abstract:

    Because plants grow under many different types of soil and environmental conditions, we investigated the hypothesis that multiple pathways for K + uptake exist in plants. We have identified a new family of Potassium Transporters from Arabidopsis by searching for homologous sequences among the expressed sequence tags of the GenBank database. The deduced amino acid sequences of AtKUP (for Arabidopsis thaliana K + uptake Transporter) cDNAs are highly homologous to the non-plant Kup and HAK1 Potassium Transporters from Escherichia coli and Schwanniomyces occidentalis , respectively. Interestingly, AtKUP1 and AtKUP2 are able to complement the Potassium Transport deficiency of an E. coli triple mutant. In addition, transgenic Arabidopsis suspension cells overexpressing AtKUP1 showed increased Rb + uptake at micromolar concentrations with an apparent K m of ~22 μM, indicating that AtKUP1 encodes a high-affinity Potassium uptake activity in vivo. A small, low-affinity Rb + uptake component was also detected in AtKUP1-expressing cells. RNA gel blot analysis showed that the various members of the AtKUP family have distinct patterns of expression, with AtKUP3 transcript levels being strongly induced by K + starvation. It is proposed that plants contain multiple Potassium Transporters for high-affinity uptake and that the AtKUP family may provide important components of high- and low-affinity K + nutrition and uptake into various plant cell types.

Thomas C Williams - One of the best experts on this subject based on the ideXlab platform.

  • evolutionary engineering in saccharomyces cerevisiae reveals a trk1 dependent Potassium influx mechanism for propionic acid tolerance
    Biotechnology for Biofuels, 2019
    Co-Authors: Thomas C Williams, Christina Divne, Isak S. Pretorius, Ian T. Paulsen
    Abstract:

    Propionic acid (PA), a key platform chemical produced as a by-product during petroleum refining, has been widely used as a food preservative and an important chemical intermediate in many industries. Microbial PA production through engineering yeast as a cell factory is a potentially sustainable alternative to replace petroleum refining. However, PA inhibits yeast growth at concentrations well below the titers typically required for a commercial bioprocess. Adaptive laboratory evolution (ALE) with PA concentrations ranging from 15 to 45 mM enabled the isolation of yeast strains with more than threefold improved tolerance to PA. Through whole genome sequencing and CRISPR–Cas9-mediated reverse engineering, unique mutations in TRK1, which encodes a high-affinity Potassium Transporter, were revealed as the cause of increased propionic acid tolerance. Potassium supplementation growth assays showed that mutated TRK1 alleles and extracellular Potassium supplementation not only conferred tolerance to PA stress but also to multiple organic acids. Our study has demonstrated the use of ALE as a powerful tool to improve yeast tolerance to PA. Potassium Transport and maintenance is not only critical in yeast tolerance to PA but also boosts tolerance to multiple organic acids. These results demonstrate high-affinity Potassium Transport as a new principle for improving organic acid tolerance in strain engineering.

  • Evolutionary engineering in Saccharomyces cerevisiae reveals a TRK1-dependent Potassium influx mechanism for propionic acid tolerance
    BMC, 2019
    Co-Authors: Thomas C Williams, Christina Divne, Isak S. Pretorius, Ian T. Paulsen
    Abstract:

    Abstract Background Propionic acid (PA), a key platform chemical produced as a by-product during petroleum refining, has been widely used as a food preservative and an important chemical intermediate in many industries. Microbial PA production through engineering yeast as a cell factory is a potentially sustainable alternative to replace petroleum refining. However, PA inhibits yeast growth at concentrations well below the titers typically required for a commercial bioprocess. Results Adaptive laboratory evolution (ALE) with PA concentrations ranging from 15 to 45 mM enabled the isolation of yeast strains with more than threefold improved tolerance to PA. Through whole genome sequencing and CRISPR–Cas9-mediated reverse engineering, unique mutations in TRK1, which encodes a high-affinity Potassium Transporter, were revealed as the cause of increased propionic acid tolerance. Potassium supplementation growth assays showed that mutated TRK1 alleles and extracellular Potassium supplementation not only conferred tolerance to PA stress but also to multiple organic acids. Conclusion Our study has demonstrated the use of ALE as a powerful tool to improve yeast tolerance to PA. Potassium Transport and maintenance is not only critical in yeast tolerance to PA but also boosts tolerance to multiple organic acids. These results demonstrate high-affinity Potassium Transport as a new principle for improving organic acid tolerance in strain engineering

David H Ellison - One of the best experts on this subject based on the ideXlab platform.

  • wnk kinases regulate sodium chloride and Potassium Transport by the aldosterone sensitive distal nephron
    Kidney International, 2006
    Co-Authors: Arohan R Subramanya, Chao Ling Yang, James A Mccormick, David H Ellison
    Abstract:

    With-No-Lysine [K] (WNKs) are a recently discovered family of serine/threonine protein kinases that contain a uniquely structured catalytic domain. Mutations in the genes encoding two family members, WNK1 and WNK4, cause a chloride-dependent, thiazide-sensitive inherited syndrome of hypertension and hyperkalemia. Over the past 5 years, physiologic studies have demonstrated that these proteins regulate transcellular and paracellular epithelial ion flux. In this mini review, we discuss WNK1 and WNK4 gene products and their regulatory effects on sodium chloride and Potassium handling in the aldosterone-sensitive distal nephron. Experimental observations regarding the effects of these proteins on Transport processes mediated by the thiazide-sensitive Na–Cl co-Transporter, the epithelial sodium channel, the renal outer medullary Potassium channel, and the paracellular pathway integrate into a model that suggests an essential role for WNKs in coordinating renal Na–Cl reabsorption and K + secretion.

David G Warnock - One of the best experts on this subject based on the ideXlab platform.

  • sodium and Potassium handling by the aldosterone sensitive distal nephron the pivotal role of the distal and connecting tubule
    American Journal of Physiology-renal Physiology, 2004
    Co-Authors: Pierre Meneton, Johannes Loffing, David G Warnock
    Abstract:

    Sodium reabsorption and Potassium secretion in the distal convoluted tubule and in the connecting tubule can maintain the homeostasis of the body, especially when dietary sodium intake is high and Potassium intake is low. Under these conditions, a large proportion of the aldosterone-regulated sodium and Potassium Transport would occur in these nephron segments before the tubular fluid reaches the collecting duct. The differences between these two segments and the collecting duct would be more quantitative than qualitative. The collecting duct would come into play when the upstream segments are overloaded by a primary genetic defect that affects sodium and/or Potassium Transport or by a diet that is exceedingly poor in sodium and rich in Potassium. It is likely that the homeostatic role of the distal convoluted and connecting tubules, which are technically difficult to study, has been underestimated, whereas the role of the more easily accessible collecting duct may have been overemphasized.

Ian T. Paulsen - One of the best experts on this subject based on the ideXlab platform.

  • evolutionary engineering in saccharomyces cerevisiae reveals a trk1 dependent Potassium influx mechanism for propionic acid tolerance
    Biotechnology for Biofuels, 2019
    Co-Authors: Thomas C Williams, Christina Divne, Isak S. Pretorius, Ian T. Paulsen
    Abstract:

    Propionic acid (PA), a key platform chemical produced as a by-product during petroleum refining, has been widely used as a food preservative and an important chemical intermediate in many industries. Microbial PA production through engineering yeast as a cell factory is a potentially sustainable alternative to replace petroleum refining. However, PA inhibits yeast growth at concentrations well below the titers typically required for a commercial bioprocess. Adaptive laboratory evolution (ALE) with PA concentrations ranging from 15 to 45 mM enabled the isolation of yeast strains with more than threefold improved tolerance to PA. Through whole genome sequencing and CRISPR–Cas9-mediated reverse engineering, unique mutations in TRK1, which encodes a high-affinity Potassium Transporter, were revealed as the cause of increased propionic acid tolerance. Potassium supplementation growth assays showed that mutated TRK1 alleles and extracellular Potassium supplementation not only conferred tolerance to PA stress but also to multiple organic acids. Our study has demonstrated the use of ALE as a powerful tool to improve yeast tolerance to PA. Potassium Transport and maintenance is not only critical in yeast tolerance to PA but also boosts tolerance to multiple organic acids. These results demonstrate high-affinity Potassium Transport as a new principle for improving organic acid tolerance in strain engineering.

  • Evolutionary engineering in Saccharomyces cerevisiae reveals a TRK1-dependent Potassium influx mechanism for propionic acid tolerance
    BMC, 2019
    Co-Authors: Thomas C Williams, Christina Divne, Isak S. Pretorius, Ian T. Paulsen
    Abstract:

    Abstract Background Propionic acid (PA), a key platform chemical produced as a by-product during petroleum refining, has been widely used as a food preservative and an important chemical intermediate in many industries. Microbial PA production through engineering yeast as a cell factory is a potentially sustainable alternative to replace petroleum refining. However, PA inhibits yeast growth at concentrations well below the titers typically required for a commercial bioprocess. Results Adaptive laboratory evolution (ALE) with PA concentrations ranging from 15 to 45 mM enabled the isolation of yeast strains with more than threefold improved tolerance to PA. Through whole genome sequencing and CRISPR–Cas9-mediated reverse engineering, unique mutations in TRK1, which encodes a high-affinity Potassium Transporter, were revealed as the cause of increased propionic acid tolerance. Potassium supplementation growth assays showed that mutated TRK1 alleles and extracellular Potassium supplementation not only conferred tolerance to PA stress but also to multiple organic acids. Conclusion Our study has demonstrated the use of ALE as a powerful tool to improve yeast tolerance to PA. Potassium Transport and maintenance is not only critical in yeast tolerance to PA but also boosts tolerance to multiple organic acids. These results demonstrate high-affinity Potassium Transport as a new principle for improving organic acid tolerance in strain engineering