Induction of salt resistance of arabidopsis salicylatedeficient transformants NahG by influence of nitric oxide donor.

The influence of treatment with the donor of nitric oxide sodium nitroprusside (SNP ­ 0,5 mM) on the salt resistance of Arabidopsis plants of wild-type (Col-0) and transformant with the gene of bacterial salicylatehydroxylase (NahG) was compared. The basic resistance against the salt stress (200 mM of NaCl) in transformants NahG was higher. In the conditions of salt stress these plants differed in the higher activity of antioxidant enzymes and the raised content of carbohydrates and anthocyans. The treatment with NO donor increased the salt resistance of plants of both genotypes that expressed in the decrease of growth inhibition, reduction of oxidative damages and preservation of chlorophyll pool in the leaves. After the influence of salt stress the activity of superoxide dismutase and guaiacol peroxidase in treated with SNP wild type plants and transformants was higher, than in the appropriate untreated plants. In the wild type plants, treated with NO donor, the content of proline in leaves after the salt stress was lower, than in untreated. The treatment with SNP of transformants NahG, on the contrary, led to more essential increase of proline content in leaves under the salt stress. The conclusion is made that plants of wild type Col-0 and transformant NahG have differences in the functioning of protective systems under the salt stress, and the induction of protective systems in A. thaliana plants under the influence of nitric oxide can occur without salicylate participation.

[Content of Osmolytes and Flavonoids under Salt Stress in Arabidopsis thaliana Plants Defective in Jasmonate Signaling].

The effects of the salt stress (200 mM NaCl) and exogenous jasmonic acid (JA) on levels of osmolytes and flavonoids in leaves of four-week-old Arabidopsis thaliana L. plants of the wild-type (WT) Columbia-0 (Col-0) and the mutant jin1 (jasmonate insensitive 1) with impaired jasmonate signaling were studied. The increase in proline content caused by the salt stress was higher in the Col-0 plants than in the mutant jin1. This difference was especially marked if the plants had been pretreated with exogenous 0.1 µM JA. The sugar content increased in response to the salt stress in the JA-treated WT plants but decreased in the jin1 mutant. Leaf treatment with JA of the WT plants but not mutant defective in jasmonate signaling also enhanced the levels of anthocyanins and flavonoids absorbed in UV-B range. The presence of JA increased salinity resistance of the Col-0 plants, since the accumulation of lipid peroxidation products and growth inhibition caused by NaCl were less pronounced. Under salt stress, JA almost did not render a positive effect on the jin1 plants. It is concluded that the protein JIN1/MYC2 is involved in control of protective systems under salt stress.

[SIGNAL MEDIATORS IN PLANTS RESPONSES AGAINST ABIOTIC STRESSORS: CALCIUM, REACTIVE OXYGEN AND NITROGEN SPECIES].

The perception of signals of abiotic stressors by plant cells is accompanied by the increase of cytosolic calcium concentration, content of reactive oxygen species (ROS) and nitrogen monoxide (NO) which execute the role of signal mediators at the activation of gene expression, supervising protective reactions. Calcium ions, ROS, and NO are in the multiple functional interactions which provides the intensifying and transduction of signals into genetic apparatus as well as their attenuation. The increase of content, at least, of one of these signal mediators in cells can cause activation of some signal cascades and formation of plant adaptive reactions.

[Role of Ca ions in the induction of heat-resistance of wheat coleoptiles by brassinosteroids].

The involvement of Ca2+ into the signal transduction of exogenous brassinosteroids (BS) (24-epi-brassinolide-24-EBL and 24-epicastasterone-24-ECS) causing the increase of heat resistance of the cells of wheat (Triticum aestivum L.) coleoptiles was investigated using calcium chelator EGTA and inhibitor of phosphatidylinositol-specific phospholipase C--neomycin. Twenty-four-hour treatment of coleoptile segments with 10 nM solutions of 24-EBL and 24-ECS led to a transient increase in the generation of superoxide anion radical by cell surface and the subsequent activation of superoxide dismutase and catalase. Pretreatment of coleoptiles with EGTA and neomycin depressed to a considerable extent these effects and leveled the increase in heat resistance of wheat coleoptiles that were caused by BS. Possible mechanisms of involvement of calcium signaling into the formation of reactive oxygen species in plant cells and induction of heat resistance of plant cells by the action of exogenous BS have been discussed.

SIGNAL MEDIATORS AT INDUCTION OF HEAT RESISTANCE OF WHEAT PLANTLETS BY SHORT-TERM HEATING.

The effects of functional interplay of calcium ions, reactive oxygen species (ROS) and nitric oxide (NO) in the cells of wheat plantlets roots (Triticum aestivum L.) at the induction of their heat resistance by a short-term influence of hyperthermia (heating at the temperature of 42 degrees C during 1 minute) have been investigated. The transitional increase of NO and H2O2 content, invoked by heating, was suppressed by the treatment of plantlets with the antagonists of calcium EGTA (chelator of exocellular calcium), lanthanum chloride (blocker of calcium channels of various types) and neomycin (inhibitor of phosphatidylinositol-dependent phospholipase C). The rise of hydrogen peroxide content, caused by hardening, was partially suppressed by the action of inhibitors of nitrate reductase (sodium wolframate) and NO-synthase (N(G)-nitro-L-arginine methyl ester--L-NAME), and the increasing of nitric oxide content was suppressed by the treatment of plants with the antioxidant ionol and with the scavenger of hydrogen peroxide (dimethylthiourea). These compounds and antagonists of calcium also partially removed the effect of the rise of plantlets' heat resistance, invoked by hardening heating. The conclusion on calcium's role in the activation of enzymatic systems, generating reactive oxygen species and nitric oxide, and on the functional interplay of these signal mediators at the induction of heat resistance of plantlets by hardening heating is made.