Effect of fatty acids on poly-amine contents and Na+/H+antiport activity in PM vesi-cles isolated from roots ofbarley under salt stress

With 200 mmol/L NaCI treatment on barleycultivar "Jian 4" (Hordeum vulgare L. cv. J4) seedlings for6 d, the contents of covalently and noncovalently conjugatedpolyamines (PAs) and activities of H+-ATPase in plasmamembrane (PM) vesicles isolated from the roots decreasedremarkably. Moreover, the activity of Na+/H+ antiport wasdetected first in PM vesicles. The results showed that thedecrease in the contents of membrane phospholipid, nonco-valently conjugated PAs and activity of H+-ATPase caused byNaCl could be restored partially by application of 1 mmol/Lstearic acid (C16:0) and linoleic acid (C18:2), and C18:2 wasmore effective than C16:0. In addition, a reduction in the con-tents of covalently conjugated PAs was only reversed par-tially in the presence of C18:2. Furthermore, Na+/H+ antiportactivity was strengthened by exogenous C16:0 and C18:2, andC18a was more effective than C16:0. The correlative analysissuggested that, after application of C16:0 and C18:2 under saltstress, there was a significant positive correlation existingamong phospholipid content, noncovalently conjugated PAlevels, H+-ATPase activities and Na+/H+ antiport activities,indicating that one of the mitigative mechanisms of exoge-nous fatty acids on salt injury was to improve membranephospholipid and PA contents, leading to an enhance inmembrane integrity and a change in charge status of PMvesicles, so the activity of membrane-associated enzymeH+-ATPase was increased and synthesis of Na+/H+ antiportprotein was activated.     

铜对小麦根质膜H+-ATPase活性的影响

用两相法提取小麦根质膜微囊,研究了铜对质膜H -ATPase活性的影响.硫酸铜(CuSO4)抑制小麦根质膜H -ATPase的活性,其作用具有浓度依赖性.金属离子螯合剂乙二胺四乙酸二钠(EDTA-Na2,200μmol.L-1)可以完全消除CuSO4对H -ATPase活性的抑制效应.检测硫代巴比妥酸反应物质(TBARS)的相对含量,结果显示Cu2 的加入使质膜微囊产生了较多的TBARS,表明Cu2 作用导致细胞膜发生较强的氧化损害.实验结果表明,CuSO4可以减弱小麦根质膜H -ATPase的活性,此效应是由Cu2 引起的;此外,Cu2 导致质膜微囊产生较强的膜脂过氧化.     

Enhanced H+ transport activity of tonoplast vesicles isolated from roots of salt-tolerant mutant of wheat under NaCl stress

Both enhanced were H⁺ transport activities of tonoplast vesicles isolated from roots of the salt-tolerant mutant and wild type of wheat with treatment of NaCl, but the activity of the mutant was significantly higher than that of wild type. H⁺ transport activity was indicated as the stable value of fluorescence quenching per mg membrane proteins. The H⁺ transport activities dependent on ATP of the mutant and wild type were 1099 and 558 respectively and their activities dependent on PPi were 358 and 228 separately.     

Reduced Na+ and K+ permeability of K+ channel in plasma membrane isolated from roots of salt-tolerant mutant of wheat

The Na⁺ and K⁺ permeability of K⁺ channel in plasma membrane, isolated from roots of the salt-tolerant mutant of wheat, was lower than that of wild type in 100 mmol/L KCl and NaCl solution. The opening frequency of K⁺ channel of the mutant reduced more significantly than that of wild type in two kinds of solution mentioned above. It is assumed that the reduction of opening frequency mainly contributes to the Na⁺ and K⁺ permeability of K⁺ channel of the mutant. The electric conductance of single-channel of the mutant was similar to that of wild type and the main difference between them was exhibited as the opening frequency. Their K⁺/Ka⁺ selectivity of K⁺ channel had no significant difference. The K⁺/Na⁺ selectivity of the mutant and wild type was 3.35 and 3.18 respectively.     

The short C-terminal hydrophilic domain of NhaH Na^＋/H^＋ antiporter from Halobacillus dabanensis with roles in resistance to salt and in pH sensing

The Na^＋/H^＋ antiporter plays key roles in maintaining low cytoplasmic NaNa^＋ level and pH homeostasis, while little is known about the Carboxyl-terminal hydrophilic tails of prokaryotic antiporters. In our previous study, the first Na^＋/H^＋ antiporter gene nhaH from moderate halophiles was cloned from Halobacillus dabanensis D-8 by functional complementation. A topological model suggested that only nine amino acid residues （^395PLIKKLGMI403） existed in the hydrophilic C-terminal domain of NhaH. The C-terminal truncated mutant of NhaH was constructed by PCR strategy and designated as nhaH△C. Salt tolerance experiment demonstrated that the deletion of hydrophilic C-terminal nine amino acid residues significantly inhibited the complementation ability of E. coil KNabc, in which three main Na^＋/H^＋ antiporters nhaA, nhaB and chaA were deleted. Everted membrane vesicles prepared from E. coil KNabc/nhaHAC decreased both Na^＋/H^＋ and Li^＋/H^＋ exchange activities of NhaH, and also resulted in an acidic shift of its pH profile for Na^＋, indicating a critical role of the short C-terminal domain of NhaH antiporter in alkali cation binding/translocation and pH sensing.     

Stable expression of Arabidopsis vacuolar Na+/H+ antiporter gene AtNHX1, and salt tolerance in transgenic soybean for over six generations

The Arabidopsis vacuolar Na+/H+ antiporter gene,AtNHX1,was introduced into soybean by Agrobacterium-mediated transformation.Four independent kanamycin resistant lines were obtained.The result of PCR,Southern blotting and Northern blotting analyses demonstrated that the AtNHX1 gene was successfully inserted into the soybean genome and stably expressed in these kanamycin resistant lines.The stability of AtNHX1 expression and salt resistance were evaluated in the soybean transformants for over 6 generations.Tw...