title: The involvement of calcium in the regulation of GPX1 expression.
abstract: Detrimental effects of salinity on plants are known to be partially alleviated by external Ca(2+). Previously we demonstrated that in citrus cells, phospholipid hydroperoxide glutathione peroxidase (GPX1) is induced by salt and its activation can be monitored by pGPX1::GUS fusion in transformed tobacco cells. In this paper we further characterized the induction of GPX1 by additional treatments, which are known to affect Ca(2+) transport. Omission of Ca(2+) changed the pattern of the transient salt-induced expression of GPX1 and chelation of Ca(2+) by EGTA, or treatment with caffeine, abolished the salt-induced GPX1 transcript. On the other hand, La(3+) was found to be as potent as NaCl in inducing GPX1 transcription and the combined effect of La(3+) and NaCl seemed to be additive. Pharmacological perturbation of either external or internal Ca(2+) pools by La(3+), EGTA, caffeine, Ca(2+) channel blockers, or a Ca(2+)-ATPase inhibitor rendered the imposed salt stress more severe. Except for La(3+), all these Ca(2+) effectors had no effect on their own. In addition, the fluidizer benzyl alcohol dramatically increased the NaCl-induced GPX1 transcription. Taken together, our results show that: 1) the mode of action of La(3+) on GPX1 expression differs from its established role as a Ca(2+) channel blocker, 2) membrane integrity has an important role in the perception of salt stress, and 3) internal stores of Ca(2+) are involved in activating GPX1 expression in response to salt stress. We propose that the common basis for these effects lies in the membrane bound Ca(2+).
authors.affiliation: Department of Plant Sciences, ARO, The Volcani Center, P.O. Box 6, 50250, Bet Dagan, Israel.
authors.forename: Yardena
authors.initials: Y
authors.lastname: Gueta-Dahan
authors.forename: Orna
authors.initials: O
authors.lastname: Avsian-Kretchmer
authors.forename: Gozal
authors.initials: G
authors.lastname: Ben-Hayyim
mesh_terms: D015152:Blotting, Northern; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D002957:Citrus / Q000166:cytology / Q000235:genetics; D004533:Egtazic Acid / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D005979:Glutathione Peroxidase / Q000235:genetics*; D007811:Lanthanum / Q000494:pharmacology; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D012965:Sodium Chloride / Q000494:pharmacology; D014026:Nicotiana / Q000166:cytology / Q000235:genetics
chemical_list: D002110:Caffeine; D012965:Sodium Chloride; D004533:Egtazic Acid; D007811:Lanthanum; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D005979:Glutathione Peroxidase; D002118:Calcium