S-Nitrosothiol Signaling Is involved in Regulating Hydrogen Peroxide Metabolism of Zinc-Stressed Arabidopsis

Accumulation of heavy metals such as zinc (Zn) disturbs the metabolism of reactive oxygen (e.g. hydrogen peroxide, H2O2) and nitrogen species (e.g. nitric oxide, NO; S-nitrosoglutathione, GSNO) in plant cells; however, their signal interactions are not well understood. Therefore, this study examines the interplay between H2O2 metabolism and GSNO signaling in Arabidopsis. Comparing the Zn tolerance of the wild type (WT), GSNO reductase (GSNOR) overexpressor 35S::FLAG-GSNOR1 and GSNOR-deficient gsnor1-3, we observed relative Zn tolerance of gsnor1-3, which was not accompanied by altered Zn accumulation capacity. Moreover, in gsnor1-3 plants Zn did not induce NO/S-nitrosothiol (SNO) signaling, possibly due to the enhanced activity of NADPH-dependent thioredoxin reductase. In WT and 35S::FLAG-GSNOR1, GSNOR was inactivated by Zn, and Zn-induced H2O2 is directly involved in the GSNOR activity loss. In WT seedlings, Zn resulted in a slight intensification of protein nitration detected by Western blot and protein S-nitrosation observed by resin-assisted capture of SNO proteins (RSNO-RAC). LC-MS/MS analyses indicate that Zn induces the S-nitrosation of ascorbate peroxidase 1. Our data collectively show that Zn-induced H2O2 may influence its own level, which involves GSNOR inactivation-triggered SNO signaling. These data provide new evidence for the interplay between H2O2 and SNO signaling in Arabidopsis plants affected by metal stress.

Factors shaping the composition of the cutaneous microbiota

From birth, we are constantly exposed to bacteria, fungi and viruses, some of which are capable of transiently or permanently inhabiting our different body parts as our microbiota. The majority of our microbial interactions occur during and after birth, and several different factors, including age, sex, genetic constitution, environmental conditions and lifestyle, have been suggested to shape the composition of this microbial community. Propionibacterium acnes is one of the most dominant lipophilic microbes of the postadolescent, sebum-rich human skin regions. Currently, the role of this bacterium in the pathogenesis of the most common inflammatory skin disease, acne vulgaris, is a topic of intense scientific debate. Recent results suggest that Westernization strongly increases the dominance of the Propionibacterium genus in human skin compared with natural populations living more traditional lifestyles. According to the disappearing microbiota hypothesis proposed by Martin Blaser, such alterations in the composition of our microbiota are the possible consequences of socioeconomic and lifestyle changes occurring after the industrial revolution. Evanescence of species that are important elements of the human ecosystem might lead to the overgrowth and subsequent dominance of others because of the lack of ecological competition. Such changes can disturb the fine-tuned balance of the human body and, accordingly, our microbes developed through a long co-evolutionary process. These processes might lead to the transformation of a seemingly harmless species into an opportunistic pathogen through bacterial dysbiosis. This might have happened in the case of P. acnes in acne pathogenesis.

Involvement of nitrate reductase in auxin-induced NO synthesis

It is well known for a long time, that nitric oxide (NO) functions in variable physiological and developmental processes in plants, however the source of this signaling molecule in the diverse plant responses is very obscure.1 Although existance of nitric oxide sythase (NOS) in plants is still questionable, LNMMA (N(G)-monomethyl-L-arginine)-sensitive NO generation was observed in different plant species.2,3 In addition, nitrate reductase (NR) is confirmed to have a major role as source of NO.4,5 This multifaced molecule acts also in auxin-induced lateral root (LR) formation, since exogenous auxin enhanced NO levels in regions of Arabidopsis LR initiatives. Our results pointed out the involvement of nitrate reductase enzyme in auxin-induced NO formation. In this addendum, we speculate on auxin-induced NO production in lateral root primordial formation.

Changes in chlorophyll fluorescence parameters and oxidative stress responses of bush bean genotypes for selecting contrasting acclimation strategies under water stress

Drought resistance of bean landraces was compared in order to select genotypes with either high morphological or high biochemical-physiological plasticity. The lines in the former group exhibited fast reduction in fresh and dry mass, decreased the water potential in primary leaves after irrigation withdrawal and the biomass mobilized from the senescent primary leaves was allocated into the roots. These genotypes had high frequency of primary leaf abscission under water stress. The genotypes with plasticity at the biochemical level maintained high water potential and photochemical efficiency, i.e. effective quantum yield, high photochemical (qP) and low non-photochemical (NPQ) quenching in primary leaves under drought stress. While superoxide dismutase activity was not influenced by the drought and the genotype, catalase activity increased significantly in the primary leaves of the genotypes with efficient biochemical adaptation. Lines with high morphological plasticity exhibited higher quaiacol peroxidase activity under drought. Proline may accumulate in both cases, thus it may be a symptom of protein degradation or a successful osmotic adaptation. On the basis of contrasting responses, the genetic material cannot be screened for a large-scale breeding program by a single physiological parameter but by a set of the methods presented in this work.

Distribution of the Mo-enzymes aldehyde oxidase, xanthine dehydrogenase and nitrate reductase in maize (Zea mays L.) nodal roots as affected by nitrogen and salinity

The distribution of the Mo-enzymes aldehyde oxidase (AO; EC 1.2.3.1) xanthine dehydrogenase (XDH; EC 1.2.1.37) and nitrate reductase (NAD(P)H NR; EC 1.6.6.1-2) was studied along the longitudinal and transversal axes of maize (Zea mays L. cv. Jubily) nodal roots as affected by nitrogen sources and salinity. Activities of the Mo-enzymes were considerably enhanced under mild saline conditions. The activities of AO and XDH increased following addition of ammonium to the nutrient solution. Immunoblot analysis with antibodies raised against maize AO protein revealed increased levels of AO proteins in root tips of ammonium fed plants. Application of salinity to nitrate fed plants did not affect the enzyme protein level, although it enhanced the activity of the Mo-hydroxylases. The specific activities of the Mo-enzymes were the highest in root tips (0-1 cm segments) while on the transversal axis maximal activity was observed in the stele or vascular cylinder. Activity staining of AO after native PAGE of root extracts revealed four bands of AO proteins (AO1-4) capable of oxidizing a number of aliphatic and aromatic aldehydes. Increased AO activity in maize nodal roots grown with ammonium, and salinity were observed mainly at the AO3 and AO4 bands. Tips and stele contained primarily AO3 and AO4, and only traces of AO1 and AO2. SDS-PAGE of root extracts followed by Western blots revealed, besides the major 150 kD subunit of AO, two polypeptides with molecular masses of 72 and 85 kD located specifically in the cortex. Part of the polymorphism of AO in plant roots may be related to the allocation of distinct isoforms to different regions of the root, although the specific metabolic roles of the different bands have not been established.

Do Selye's mammalian "GAS" concept and "co-stress" response exist in plants?

Converging data indicate the possible existence of a general adaptation syndrome (GAS) in which different types of stress evoke identical coping mechanisms. In Selyean terms, this implies a "co-stress" response whereby one type of stress resistance may impart co-resistance to others. Common coping denominators may be physiological or morphological. The former include oxy-free radical scavenging, osmoregulation, ABA, jasmonates, chaperones, HSPs, and phytochelatins. Morphological GAS adaptations include leaf pubescence, movements and stance, and rooting characteristics. The feasibility, with certain reservations, of the GAS hypothesis is discussed here.

Isolation of a wheat cell line with altered membrane properties

A spontaneous dimethylsulfoxide (DMSO)-tolerant cell line was isolated from a cell culture of wheat (Triticum monococcum L.). The tolerant cells were able to grow in the presence of 4% DMSO. Cells formed from protoplasts of the tolerant line required DMSO for division in culture medium of high osmotic value.Fatty acid composition and the molar ratio of phospholipids/sterols suggest a more ordered membrane structure in the tolerant line. Accordingly, a lower K(+) influx rate was detected in the tolerant cells in comparison with the original line. These characteristics were maintained after 6 months' cultivation of the cells in DMSO-free growth medium. This suggested that genetic changes could be responsible for differences between the two cell lines.

Simple, rapid method for detecting phase transititons of lipids

A simple rapid method was worked out for studying the physical and structural state of lipids by measuring the refractive indices of a layered lipid film. Melting processes of n-paraffins and phase transitions of phospholipids and the lecithin-cholesterol system also can be followed as a function of temperature. In accordance with data from the relevant literature, the measured refractive indices show that cholesterol lowers the phase transition temperature of lecithin. By isorefraction curves, the most ordered structure of the layers is indicated to occur at the equimolar ratio of cholesterol and lecithin. The method may be applied to study the effect of lipid-soluble agents upon lipid structure and is applicable for routine investigations and industrial purposes as well.