Nitrogen Source Differently Regulates Barley (Hordeum vulgare) Response to NaCl Stress At Seed Germination and Early Seedling Development Stages

Nitrogen (N) acts as nutrient and signaling molecule in plants all over their development stages. The involvement of various N forms in the regulation of seed germination response to salt stress was assessed in the present work. Nitrogen sources (NO, NO2−, NO3−, NH4+, glutamine and glutamate) were added at 1mMto the germination medium of barley (Hordeum vulgare, cv Ardhaoui) in combination or not with NaCl stress (14 g.L−1). The application of nitrogen monoxide (NO) alleviated by about 20% the NaCl-induced germination capacity decrease. However, the addition of ammonium ions (NH4+) and glutamic acid (Glu) accentuated the inhibitory effects of NaCl, decreasing germination capacity by about 50% compared to the control. The levels of malondialdehyde (MDA), which is an indicator of membrane lipid peroxidation by stresses, were increased by salinity in seeds treated with nitrite (NO2−), NO3−, Glu and Gln. In N-free medium, NaCl stress induced a severe nitrate reductase activity (NR, EC 1.6.1.6) inhibition. Such an effect was alleviated by the application of N treatments. Glutamate dehydrogenase (GDH, EC 1.4.1.2) aminating activity (NADH-GDH) of seedlings was inhibited by NaCl stress in the presence of NO, Glu and Gln. Conversely, there was stimulation by salt stress of NADH-GDH activity in seedlings treated with NaCl and NH4+. Deaminating GDH activity (NAD-GDH) was found to be enhanced by salt stress in NO2− and NO3− treatments. The differential effects of applied N forms on germination and early seedling development processes in this grass probably underlines different regulatory actions within N mobilization and assimilation

Protective effect of Atriplex halimus extract against benzene-induced haematotoxicity in rats

Benzen (BZ) is a ubiquitous environmental pollutant with a toxic effect mainly aimed at the hematopoietic­ and immune systems. Atriplex halimus L. (Amaranthaceae) is a Mediterranean halophytic shrub traditionally used in North Africa as medicinal plant for several therapeutic uses. The present study aimed to estimate the preventive and curative effects of Atriplex halimus L. (Ah) aqueous extract against BZ-induced hematotoxici­ty in rats. Analysis of the extract by the method of LC-MS revealed the presence of 7 vitamins, among which vitamin C content was the highest. Adult rats were divided into five groups as follow: Group 1 received water (control); Group 2 received orally Ah aqueous extract (200 mg/kg) 3 days/week for 15 weeks; Group 3 received BZ (100 mg/kg b.w) daily in drinking water for 15 weeks; Group 4 received concomitantly BZ (100 mg/kg) and preventive treatment with Ah (200 mg/kg) for 15 weeks (AhP+BZ); Group 5 first received BZ (100 mg/kg) for 11 weeks and then curative treatment with Ah extract (300 mg/kg) daily for 30 days (BZ+AhC). It was shown that sub-chronic exposure to benzene induced leukopenia, lymphocytopenia, granulocytopenia and massive degeneration of the bone marrow tissue. The level of GSH and activity of GST and CAT were significantly lowered and the level of MDA was increased in the blood and bone marrow in rats of BZ-intoxicated group compared to the control rats. Administration of Ah extract recovered the bone marrow structure, dramatically decreased MDA content and increased GSH and CAT activity and GST level in the blood and bone marrow as compared with the indices in BZ-treated group. These observations demonstrate that curative and, to a lesser extent, preventive treatment with Atriplex halimus extract have therapeutic potential against hematotoxicity induced by benzene

The Cys-Arg/N-end rule pathway is a general sensor of abiotic stress in flowering plants

Abiotic stresses impact negatively on plant growth, profoundly affecting yield and quality of crops. Although much is known about plant responses, very little is understood at the molecular level about the initial sensing of environmental stress. In plants, hypoxia (low oxygen, which occurs during flooding) is directly sensed by the Cys-Arg/N-end rule pathway of ubiquitin-mediated proteolysis, through oxygen-dependent degradation of group VII Ethylene Response Factor transcription factors (ERFVIIs) via amino-terminal (Nt-) cysteine [1, 2]. Using Arabidopsis (Arabidopsis thaliana) and barley (Hordeum vulgare), we show that the pathway regulates plant responses to multiple abiotic stresses. In Arabidopsis, genetic analyses revealed that response to these stresses is controlled by N-end rule regulation of ERFVII function. Oxygen sensing via the Cys-Arg/N-end rule in higher eukaryotes is linked through a single mechanism to nitric oxide (NO) sensing [3, 4]. In plants, the major mechanism of NO synthesis is via NITRATE REDUCTASE (NR), an enzyme of nitrogen assimilation [5]. Here, we identify a negative relationship between NR activity and NO levels and stabilization of an artificial Nt-Cys substrate and ERFVII function in response to environmental changes. Furthermore, we show that ERFVIIs enhance abiotic stress responses via physical and genetic interactions with the chromatin-remodeling ATPase BRAHMA. We propose that plants sense multiple abiotic stresses through the Cys-Arg/N-end rule pathway either directly (via oxygen sensing) or indirectly (via NO sensing downstream of NR activity). This single mechanism can therefore integrate environment and response to enhance plant survival

Effect of drought on growth, photosynthesis and total antioxidant capacity of the saharan plant Oudeneya africana

Plants in arid and semi-arid regions are often exposed to adverse environmental conditions such as drought which can affect plant growth. In this study, we investigate the physiological responses of Oudneya africana to drought, using two different irrigation regimes (treatment 1: 50 % field capacity; treatment 2: 25 % FC), a 10- and 20-d time course analysis and a 5-d re-watering period following drought. Our results show that water deficiency reduced growth mainly in T2 plants after 20 d of treatment, with a reduction of 26 % in plant height, 64 % in leaf numbers and of 39 % in leaf area, as well as a significant decrease (50 %) in the photosynthesis rate and chlorophyll content. While both instantaneous (A/E) and intrinsic (A/gs) water use efficiency were observed to increase by 96.3 % and 173.20 %, respectively, stomatal closure increased with time and the severity of drought, mainly in the abaxial side (50 %), as evidenced by gs and Ci/Ca data. Polyphenols, flavonoids and total antioxidant capacity increased close to 2−3-fold, with increasing drought stress severity. Re-watering led to a recovery in most of the parameters analyzed, mainly the photosynthetic parameters, while antioxidant capacity remained high. Given these results, the plasticity of photosynthesis and the high antioxidant capacity of O. africana appear to contribute to its tolerance to drought.This study was co-funded by the European Regional Development Fund (ERDF) and the Spanish Ministry of Science, Innovation and Universities (grant PGC2018-098372-B-I00)