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Low K+ (low + k+)
Selected AbstractsPhysiological Responses of Krishum (Iris lactea Pall. var. chinensis Koidz) to Neutral and Alkaline SaltsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2008Y. Wang Abstract The aims of this study were to compare the physiological responses of krishum (Iris lactea Pall. var. chinensis Koidz) to neutral and alkaline salt stress and identify and examine the mechanisms involved in plant response to salt treatments. In this study, biomass, ion accumulation (Na+, K+, Ca2+, Mg2+), organic solute (proline) concentration, rate of membrane electrolyte leakage (REL) and antioxidase activities including those of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7) were investigated in krishum under different concentrations of NaCl, Na2CO3 and the mixture of the two salts in the same volume. All three treatments caused increases in Na+ concentration, proline content and REL and decreases in root Mg2+ and K+ content. Increased Ca2+ and antioxidase activities were observed at lower external Na+ concentrations. However, at higher external Na+ levels, decreased Ca2+ and antioxidase activities were detected. Alkaline salt resulted in more damage to krishum than neutral salt including lower SOD, POD and CAT activities and decreased proline content, relative to neutral salt. High Na+ and low K+ in krishum intensified ion toxicity under alkaline condition. Alkaline salt caused greater harm to plants than neutral salt, the primary reason of which might be the lower Ca2+ content in the plant under alkaline salt stress. [source] Apoptosis in cerebellar granule neurons is associated with reduced interaction between CREB-binding protein and NF-,BJOURNAL OF NEUROCHEMISTRY, Issue 2 2003Asligul Yalcin Abstract Cerebellar granule neurons undergo apoptosis when switched from medium containing depolarizing levels of potassium (high K+ medium, HK) to medium containing low K+ (LK). NF-,B, a ubiquitously expressed transcription factor, is involved in the survival-promoting effects of HK. However, neither the expression nor the intracellular localization of the five NF-,B proteins, or of I,B-, and I,B-,, are altered in neurons primed to undergo apoptosis by LK, suggesting that uncommon mechanisms regulate NF-,B activity in granule neurons. In this study, we show that p65 interacts with the transcriptional co-activator, CREB-binding protein (CBP), in healthy neurons. The decrease in NF-,B transcriptional activity caused by LK treatment is accompanied by a reduction in the interaction between p65 and CBP, an alteration that is accompanied by hyperphosporylation of CBP. LK-induced CBP hyperphosphorylation can be mimicked by inhibitors of protein phosphatase (PP) 2A and PP2A-like phosphatases such as okadaic acid and cantharidin, which also causes a reduction in p65,CBP association. In addition, treatment with these inhibitors induces cell death. Treatment with high concentrations of the broad-spectrum kinase inhibitor staurosporine prevents LK-mediated CBP hyperphosphorylation and inhibits cell death. In vitro kinase assays using glutathione- S -transferase (GST)-CBP fusion proteins map the LK-regulated site of phosphorylation to a region spanning residues 1662,1840 of CBP. Our results are consistent with possibility that LK-induced apoptosis is triggered by CBP hyperphosphorylation, an alteration that causes the dissociation of CBP and NF-,B. [source] The Na+ transporter AtHKT1;1 controls retrieval of Na+ from the xylem in ArabidopsisPLANT CELL & ENVIRONMENT, Issue 4 2007ROMOLA JANE DAVENPORT ABSTRACT HKT-type transporters appear to play key roles in Na+ accumulation and salt sensitivity in plants. In Arabidopsis HKT1;1 has been proposed to influx Na+ into roots, recirculate Na+ in the phloem and control root : shoot allocation of Na+. We tested these hypotheses using 22Na+ flux measurements and ion accumulation assays in an hkt1;1 mutant and demonstrated that AtHKT1;1 contributes to the control of both root accumulation of Na+ and retrieval of Na+ from the xylem, but is not involved in root influx or recirculation in the phloem. Mathematical modelling indicated that the effects of the hkt1;1 mutation on root accumulation and xylem retrieval were independent. Although AtHKT1;1 has been implicated in regulation of K+ transport and the hkt1;1 mutant showed altered net K+ accumulation, 86Rb+ uptake was unaffected by the hkt1;1 mutation. The hkt1;1 mutation has been shown previously to rescue growth of the sos1 mutant on low K+; however, HKT1;1 knockout did not alter K+ or 86Rb+ accumulation in sos1. [source] A role for HKT1 in sodium uptake by wheat rootsTHE PLANT JOURNAL, Issue 2 2002Sophie Laurie Summary The high affinity potassium transporter, HKT1 from wheat was introduced into Florida wheat in sense and antisense orientation under control of a ubiquitin promoter. Ten transgenic lines expressing the transgene were identified and two of these showed strong down-regulation of the native HKT1 transcript. One line (271) was expressing the antisense construct and the other (223) was expressing a truncated sense construct. The two lines were examined further for phenotype relating to cation transport. Membrane depolarisations were measured in low (0.1 mm) K+ and high (100 mm) NaCl. Under these conditions there was no difference between line 271 and the control at low K+, but at high Na+ there was a rapid depolarisation that was significantly larger in control plants. 22Na uptake was measured in this line and there was a significant decrease in uptake at 100 mm NaCl in the transgenic line when compared with the control. The two transgenic lines were grown at high NaCl (200 mm) and analysed for growth and root sodium content. Lines 271 and 223 showed enhanced growth under salinity when compared with the control and had lower sodium in the root. Secondary ion mass spectrometry (SIMS) analysis of transverse sections of the root showed that Na+ and K+ were strongly localised to stelar regions when compared with other ions, and that the Na+ : K+ ratios were reduced in salt-stressed transgenic tissue when compared with the control. [source] | ||||||||||