Search

Prosopis strombulifera (Lam.) Benth. is a halophytic shrub abundant in high-salinity areas in central Argentina, with high tolerance against NaCl but strong growth inhibition by Na2SO4. In the present study, the modulation of the antioxidant systems (enzymatic and non-enzymatic components) was analyzed under different salt treatments (NaCl, Na2SO4 and the iso-osmotic mixture) in hydroponic cultivation. Na2SO4-treated plants showed strong indications of oxidative stress (H2O2 and O2-• increase). Modifications in antioxidant enzymes activities were observed mainly under Na2SO4 treatment, where CAT seems to play an important role in early detoxification of H2O2 in roots, whereas SOD and APX have a predominant role in leaves. As part of the non-enzymatic system, 21 compounds were identified in leaves, being polyphenols the most abundant. Control plants contained the major variety of detected phytochemicals (14). Na2SO4-treated plants contained 10 compounds and NaCl-treated plants nine compounds, but with a different profile. NaCl-treated plants showed the highest antioxidant capacity. Our findings confirm that different types of salt treatments provoke a differential modulation of the antioxidant systems. Polyphenols and other ROS-detoxifying compounds, in a joint action with the enzymatic antioxidant system, are proposed to have a fundamental role in the cellular protection of P. strombulifera plants under severe oxidative stress. Our findings also highlight the potential of this halophyte as a valuable source of bioactive compounds with high antioxidant activity and health benefits.

Prosopis strombulifera (Lam.) Benth. is a halophytic shrub found in highly saline soils in Argentina, with high tolerance against NaCl but strong growth inhibition by Na2SO4. In the present study, the differences in the physiological responses caused by these salts and an iso-osmotic combination thereof on photosynthesis, mineral composition and metabolism were analyzed. Na2SO4 treated plants were the most affected by salinity, showing a significant decrease in several photosynthetic parameters. Proline and cysteine accumulated significantly in the plants in response to salt stress. These results show by the first time that the SO42− anion is triggering damage in the photosynthetic apparatus and consequently affecting the photosynthetic process, which may explain the strong growth inhibition in these plants at high salinity. Moreover, the SO42− anion provoke challenges in the incorporation of nutrients, decreasing the levels of K, Ca, P and Mg, and inducing a strong antioxidant activity in P. strombulifera. Fil: Reginato, Mariana Andrea. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones Agrobiotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Agrobiotecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Botánica. Laboratorio de Fisiología Vegetal; Argentina Fil: Turcios, Ariel E.. Leibniz Universitat Hannover; Alemania Fil: Luna, Maria Virginia. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Botánica. Laboratorio de Fisiología Vegetal; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones Agrobiotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Agrobiotecnológicas; Argentina Fil: Papenbrock, Jutta. Leibniz Universitat Hannover; Alemania

Sulfurtransferases (Str) comprise a group of enzymes widely distributed in archaea, eubacteria, and eukaryota which catalyze the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors. Neither the in vivo sulfur donors nor the acceptors of Str could be clearly identified in any of the organisms investigated so far. In Oryza sativa L. 24 Str (OsStr) encoding genes have been identified and subdivided into six groups according to their sequence homology. To half of the Oryza Str a direct homolog and to 40% at least a similar protein in Arabidopsis thaliana (L.) Heynh. could be allocated. Only the group comprising two-domain Str contains more Oryza Str than Arabidopsis Str. According to EST abundance analysis most of the OsStr mRNAs accumulate in several plant tissues. OsStr22, the homolog to the best characterized Str1 from Arabidopsis (AtStr1), shows the highest expression in middle-aged plants whereas AtStr1 shows the highest expression in senescent plants. Heterologously expressed and purified OsStr22 shows very low enzyme activity in comparison to the Arabidopsis and the Brassica napus L. Str. The data obtained so far constitute the basis to analyze differences among the Str family from monocotyledonous and dicotyledonous plants.

Aster tripolium L. (Dollart, Germany) and Sesuvium portulacastrum L. (Dakhla, Morocco) are potential halophytic vegetables, fodder plants, and ornamentals for re-vegetating saline land. To compare their strategies involved in salt tolerance both plants were grown with 0%, 1.5%, and 3% ( Aster ) or 0%, 2.5%, and 5% ( Sesuvium ) NaCl in the watering solution. The growth rate was reduced in both species with increasing NaCl concentrations. The quotient of Na + /K + indicates that Aster accumulates more K + in comparison to Na + while the reverse is true for Sesuvium . Osmolality of the leaf sap increased with increasing NaCl concentration in both Aster and Sesuvium . Transpiration rate was severely reduced in both Aster (3%) and Sesuvium (5%) plants after 10 d of NaCl watering. The CO 2 assimilation rate decreased in Aster (3%) and Sesuvium (5%) NaCl-treated plants from day 5 to day 10. The most important results from chlorophyll fluorescence measurements were derived from the non-photochemical quenching analysis (NPQ). First, both plants had linearly increasing levels of NPQ with increasing NaCl concentrations. Second, Sesuvium had almost half the NPQ value when compared to Aster under increased soil salinity. In Aster P-ATPase activities were decreased in plants treated with 3% NaCl after three days of treatment, F-ATPase activities increased with increasing NaCl concentrations and no clear changes were measured in V-ATPase activities. In Sesuvium any changes could be observed in the three ATPase activities determined. To conclude, Aster and Sesuvium use different strategies in adaptation to soil salinity.

The last step in cysteine biosynthesis is catalysed by the pyridoxal 5’-phosphate-dependent enzyme O -acetyl-L-serine(thiol)lyase (OAS-TL). Several isoforms are localized in different compartments of the cell. OAS-TL and OAS-TL-like proteins also catalyse the formation of β-cyanoalanine and sulfide; the release of sulfide and of an unknown product was also observed. In Arabidopsis plants of different age, the OAS-TL activity decreased with increasing age whereas the enzymatical sulfide release from cysteine increased in older plants. The β-cyanoalanine synthase showed two activity peaks during the time course investigated. During a 12-h light/12-h dark rhythm, the OAS-TL and the sulfide-releasing activities ran parallel with a maximum in the light phase and a decrease of enzyme activity in the dark phase. β-Cyanoalanine synthase activities did not follow a special pattern. Three genes coding for the OAS-TL isoforms A, B, and C, which are presumably localized in the cytoplasm, in plastids, and in mitochondria, respectively, were differentially expressed. The mRNA steady-state levels of the three proteins varied at different developmental stages. The results are discussed with respect to the physiological relevance in the plant organism.