Durum wheat seedlings in saline conditions: Salt spray versus root-zone salinity

Salinity is an increasingly serious problem with a strong negative impact on plant productivity. Though many studies have been made on salt stress induced by high NaCl concentrations in the root-zone, few data concern the response of plants to saline aerosol, one of the main constraints in coastal areas. In order to study more in depth wheat salinity tolerance and to evaluate damage and antioxidant response induced by various modes of salt application, seedlings of Triticum turgidum ssp. durum, cv. Cappelli were treated for 2 and 7 days with salt in the root-zone (0, 50 and 200 mM NaCl) or with salt spray (400 mM NaCl + 0 or 200 mM NaCl in the root-zone). Seedlings accumulated Na+ in their leaves and therefore part of their ability to tolerate high salinity seems to be due to Na+ leaf tissue tolerance. Durum wheat, confirmed as a partially tolerant plant, shows a higher damage under airborne salinity, when both an increase in TBA-reactive material (indicative of lipid peroxidation) and a decrease in root growth were recorded. A different antioxidant response was activated, depending on the type of salt supply. Salt treatment induced a depletion of the reducing power of both ascorbate and glutathione while the highest contents of proline were detected under salt spray conditions. In the short term catalase and ascorbate peroxidase co-operated with glutathione peroxidase in the scavenging of hydrogen peroxide, in particular in salt spray-treated plants. From our data, the durum wheat cultivar Cappelli seems to be sensitive to airborne salinity

Taking control : Hijacking of Rab GTPases by intracellular bacterial pathogens

Work in the Spanò laboratory is supported by the Wellcome Trust (grant no. 109680/Z/15/Z), the Royal Society (grant no. RG150386), and the BBSRC (grant no. BB/N017854/1). Work in the Galán laboratory is supported by the National Institute of Allergy and Infectious Diseases (grants AI055472 and AI079022 to J.E.G.).Peer reviewedPostprin

Morpho-anatomical and physiological traits of Agrostis castellana living in an active geothermal alteration field

Agrostis castellana is one of the few plants colonizing one of the most extreme geothermal alteration fields characterized by low pH and high temperature of soil. The study of species surviving in these multi-stress habitats can help to know more in deep the adaptive ability of plants. In this work morpho-anatomical, functional and physiological traits of leaves of A. castellana living few meters from fumaroles were studied, focusing on their putative ecological significance. Some typical xeromorphic traits occurred in the leaves of these plants: abundant cutinization, cell wall thickening, slightly convolute and adaxially ribbed leaf blades, tissutal reinforcements by sclereids, pubescence, protected stomata and densely packed mesophyll. Abundant pectins, important in both water balance adjusting and as monosaccharide source, were observed in epidermal cell walls. Despite the low value of relative water content, indicative of a disturbed hydric state, oxidative damage, in terms of lipid peroxidation, indicative of membrane damage, was significantly lower than in other plants of the same environment, probably tanks to an adequate antioxidant response based mainly on enzymatic machinery. Interestingly catalase activity was not inhibited by extreme conditions of the geothermal alteration field as in other plants of the same habitat. In conclusion, a cooperation of xeromorphic traits and antioxidant response seems to make A. castellana able to survive in such a prohibitive environment

Study of functional and physiological response of co-occurring shrub species to the Mediterranean climate

The Mediterranean basin is characterised by increasingly dry summers and the study of the adaptive traits developed by plants living in this stressful environment is of great interest, also in relation to climate projections for this area. Cistus monspeliensis, Myrtus communis and Phillyrea angustifolia are three co-occurring shrubs typical of the Mediterranean maquis. Their functional and physiological parameters were studied in spring, summer and autumn in order to highlight adjustments of these traits and to test eventual different adaptive strategies. Soil and leaf chemical characteristics were determined in the different seasons. Leaf area, specific leaf area, leaf dry matter content, succulence index, pigment contents hydric status and main markers of oxidative stress and antioxidant response were detected. The stressful summer season induced disturbance in hydric balance, decrease in succulence index and chlorophyll content and high contents of hydrogen peroxide. Thanks to higher enzymatic activities and total glutathione content, in the two evergreen species M. communis and P. angustifolia oxidative damage remained at levels equal to or lower than the other seasons. Only in the semideciduous C. monspeliensis both functional and biochemical traits showed a higher stress condition in summer. The higher stability of functional traits in the two evergreen species may be explained by the sclerophyllous nature of their leaves. Four environmental variables – Tmax, Tmin, soil conductivity and organic matter – mostly influenced NMDS segregation of these species

Response of Pteris vittata to different cadmium treatments

Pteris vittata is known as an arsenic hyperac- cumulator, but there is little information about its tolerance to cadmium and on its ability to accumulate this heavy metal. Our aim was to analyse the accumulation capacity, oxidative stress and antioxidant response of this fern after cadmium treatments. Cadmium content, main markers of oxidative stress and antioxidant response were detected in leaves of plants grown in hydroponics for both short- (5 days) and long- (15 days) term exposure to 0 (control) 60 and 100 lM CdCl2. In leaves, the concentration of cadmium and oxidative stress were parallel with the increase of cadmium exposure. In the short-term exposure, antioxidant response was sufficient to contrast cadmium phytotoxicity only in 60 lM cadmium-treated plants. In the long-term exposure all treated plants, in spite of the increase in activity of some peroxide-scavenging enzymes, showed a significant increase in oxidative damage. As in the long-term stress markers were comparable in all treated plants, with no clear correlation with hydrogen peroxide content, at least part of cadmium-induced oxidative injury seems not mediated by H2O2. Based on our studies, P. vittata, able to uptake relatively high concentrations of cadmium, is only partially tolerant to this heavy metal

Rab32 restriction of intracellular bacterial pathogens

Experiments in the authors’ laboratory are supported by the Wellcome Trust (grant no. 109680/Z/15/Z), the Royal Society (grant no. RG150386), and Tenovus Scotland (grant no. G14/19) to SS. VSC is recipient of a European Union’s Horizon 2020 research and innovation programme Marie Sklodowska Curie Fellowship (grant no. 706040).Peer reviewedPublisher PD

Ageing in embryos from wheat grains stored at different temperatures: oxidative stress and antioxidant response

In the present work we studied oxidative stress as an important cause of seed deterioration during ageing in embryos from durum wheat grains stored at room temperature and at low temperature (10°C). The protective role of low temperature on seed viability was confirmed. The increase of hydrogen peroxide content during dry storage was strongly correlated with the decrease of germinability. Ascorbate and glutathione showed a good correlation with grain germinability and significantly increased upon imbibition, in particular in embryos from viable grains. Ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX) and catalase (CAT) were studied quantitatively (enzymatic assays). APX, GR, and GPX were also studied qualitatively by native PAGE. The enzymes were active in dry, still viable, embryos whereas no activity was detected in non-viable embryos. With the exception of APX, all enzymatic activities decreased upon imbibition. The study of grains stored in different conditions indicated a negative correlation between the efficiency of the antioxidant enzymatic machinery and the age of the grain. The differences detected in differently stored materials confirmed that both germination parameters and the length of storage period are important in determining grain condition

Responses to desiccation injury in developing wheat embryos from naturally- and artificially-dried grains

Grains of wheat (Triticum durum Desf. cv. Cappelli) were collected at different stages of maturation. To test whether the response to desiccation injury is correlated with physiological stage and/or water content, one lot of grains at each stage was artificially dried until its water content was comparable to that of the subsequent stage. Several stress parameters were analysed in embryos isolated from naturally-and artificially-dried grains. In particular, the content of dehydrins, hydrogen peroxide and the activity of ribonucleases and of antioxidant enzyme were studied. Neutral ribonucleases, unlike acidic ones, seemed to be correlated with grain water content. In parallel with these analyses the presence of dehydrins was also examined. Dehydrin accumulation was found to vary with drying rate, and more isoforms of dehydrin were present in artificially dried than in naturally-dried grains. Artificial drying resulted in accumulation of hydrogen peroxide, while the content of this molecule was much lower in embryos from naturally fully-ripened grains. While the activities of ascorbate peroxidase (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), glutathione reductase (GR, EC 1.6.4.2), and glutathione peroxidase (GPX, EC 1.11.1.9), were generally higher early in maturation, the activity of catalase (CAT, EC 1.11.1.6) increased in mid-maturation and decreased in fully-ripe embryos. Different protective mechanisms seem to act in combination but their relative importance changes as maturation progresses and in response to the drying method

Antioxidant response to cold stress in two oil plants of the genus Jatropha

Jatropha curcas and J. macrocarpa, suitable for production of biodiesel oil from their seeds, are able to live in arid and semi-arid regions, where most crops cannot survive. J. curcas is characterized by higher oil quality and seed yield, but it is not a good candidate for oil production in arid areas with freezing temperatures, due to its sensitiv- ity to chilling in comparison to J. macrocarpa. In this work, for the first time, the effects of cold stress and different mechanisms activated in these conditions have been studied in the two species. Seedlings were treated with low non-freezing temperatures with or without a previous acclimation period. Water status, pigment content, oxida- tive stress and antioxidant response were studied in acclimated and non-acclimated plants. The key features that differentiate J. macrocarpa from J. curcas were the ability to accumulate, at low temperatures, high concentrations of pigments and glutathione and significantly higher activities of ascorbate peroxidase. These data could explain the greater resistance to low temperatures of J. macrocarpa. A period of acclimation was not able to improve cold toler- ance of J. curcas and this confirms its limited adaptability to arid areas with freezing temperatures

VARP and Rab9 Are Dispensable for the Rab32/BLOC-3 Dependent Salmonella Killing

ACKNOWLEDGMENTS: We are grateful to Juan S. Bonifacino for his generous gift pCI-neoHA-HPS1 and pCI-neo-Myc-HPS4 plasmids.We also thank to Leigh Knodler for her generous gift of P22 phage.We thank members of SS laboratory for their continuous help for technical advice. FUNDING: This work was supported by the Wellcome Trust (Seed Award 109680/Z/15/Z), the European Union’s Horizon 2020 ERC consolidator award (2016-726152-TYPHI), the BBSRC (BB/N017854/1), the Royal Society (RG150386), and Tenovus Scotland (G14/19) to SS.Peer reviewedPublisher PD