title: A novel fluorescence imaging approach to monitor salt stress-induced modulation of ouabain-sensitive ATPase activity in sunflower seedling roots.
abstract: Seedlings exposed to salt stress are expected to show modulation of intracellular accumulation of sodium ions through a variety of mechanisms. Using a new methodology, this work demonstrates ouabain (OU)-sensitive ATPase activity in the roots of sunflower seedlings subjected to salt stress (120 mM NaCl). 9-Anthroylouabain (a derivative of ouabain known to inhibit Na(+), K(+) -ATPase activity in animal systems, EC 3.6.3.9) has been used as a probe to analyze OU-sensitive ATPase activity in sunflower (Helianthus annuus) seedling roots by spectrofluorometric estimation and localization of its spatial distribution using confocal laser scanning microscopy. Salt stress for 48 h leads to a significant induction of OU-sensitive ATPase activity in the meristematic region of the seedling roots. Calcium ions (10 mM) significantly inhibit enzyme activity and a parallel accumulation of sodium ions in the cytosol of the columella cells, epidermis and in the cells of the meristematic region of the roots is evident. As a rapid response to NaCl stress, the activity of OU-sensitive ATPase gets localized in the nuclear membrane of root protoplasts and it gets inhibited after treatment with calcium ions. Nuclear membrane localization of the OU-sensitive ATPase activity highlights a possible mechanism to efflux sodium ions from the nucleus. Thus, a correlation between OU-sensitive ATPase activity, its modulation by calcium ions and accumulation of sodium ions in various regions of the seedling roots, has been demonstrated using a novel approach in a plant system.
authors.affiliation: Laboratory of Plant Physiology and Biochemistry, Department of Botany, University of Delhi, Delhi, 110007, India.
authors.forename: Soumya
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Satish Chander
authors.initials: SC
authors.lastname: Bhatla
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006368:Helianthus / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence / Q000379:methods*; D009685:Nuclear Envelope / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D019441:Plant Epidermis / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism; D015203:Reproducibility of Results; D036226:Seedlings / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013053:Spectrophotometry
chemical_list: D004791:Enzyme Inhibitors; D012965:Sodium Chloride; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D002118:Calcium