Impact of superparamagnetic iron oxide nanoparticles (SPIONs) and ionic iron on physiology of summer squash (Cucurbita pepo): A comparative study.

This study investigates the effect of SPIONs (superparamagnetic iron oxide nanoparticles, ∼12.5 nm in size) on summer squash plant (Cucurbita pepo) in the presence and absence of supplementary iron (Fe(II)-EDTA). The plants were grown in nutrient solution with different iron sources: (i) Fe(II)-EDTA, (ii) without Fe(II)-EDTA (iii) SPIONs only, and (iv) Fe(II)-EDTA with SPIONs. Plant growth and development were assessed after 20 days of soaking by measuring phenological parameters such as plant biomass, chlorophyll content, amount of carotenoids, and the catalase enzyme activity. Transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy, X-ray diffraction, and vibrating sample magnetometer methods were used to detect uptake and translocation of SPIONs in plant tissues. Our results showed that SPIONs treatment (without Fe(II)-EDTA) caused growth retardation and decreased the plant biomass and chlorophyll content. Hence, they are not efficient sources to compensate for iron demand of squash plant. Electron microscopy observations, magnetization and elemental analyses revealed that SPIONs are taken-up by plant roots but not translocate to upper organs. In roots, SPIONs use a symplastic route for intercellular transfer. These findings suggest that as an iron source, SPIONs alone are not efficient for plant growth, but can contribute it together with Fe(II)-EDTA.

Exogenous γ-aminobutyric acid treatment improves the cold tolerance of zucchini fruit during postharvest storage.

This work examines the effect of a treatment with 1 mM of γ-aminobutyric acid (GABA) on zucchini fruit during postharvest cold storage. Specifically, the effect of GABA on postharvest quality was measured, as well as its implication in the GABA shunt and other related metabolic pathways. The treatments were performed in Sinatra, a variety of zucchini highly sensitive to low-temperature storage. The application of GABA improved the quality of zucchini fruit stored at 4 °C, with a reduction of chilling-injury index, weight loss, and cell death, as well as a lower rate of electrolyte leakage. GABA content was significantly higher in the treated fruit than in the control fruit at all times analyzed. At the end of the storage period, GABA-treated fruit had higher contents of both proline and putrescine. The catabolism of this polyamine was not affected by exogenous GABA. Also, over the long term, the treatment induced the GABA shunt by increasing the activities of the enzymes GABA transaminase (GABA-T) and glutamate decarboxylase (GAD). GABA-treated fruit contained higher levels of fumarate and malate than did non-treated fruit, as well as higher ATP and NADH contents. These results imply that the GABA shunt is involved in providing metabolites to produce energy, reduce power, and help the fruit to cope with cold stress over the long term.

Actividad antibacteriana del extracto total de hojas de Cucurbita moschata Duchesne (Ahuyama) / Antibacterial activity of total extract from leaves of Cucurbita moschata Duchesne (ahuyama)

Introduction: Cucurbita moschata Duchesne (ahuyama) is grown across America as well as in the Middle East and Europe. It has been used as alternative medicine since ancient times. In the northern section of the department of Bolívar, Colombia, the plant is used by peasants to treat skin infections, hence our interest in conducting this study. Objective: Evaluate the antibacterial activity of total extract from leaves ofC. moschata against Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. Methods: Fresh leaves of C. moschata were classified taxonomically using standard methods. The leaves were dried in an oven and pulverized in a blade mill. Extraction was performed by cold solid-liquid percolation and concentration in a rotary evaporator. Antibacterial activity of the ethanolic and hexanic extracts was evaluated in vitro against methicillin-resistant Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae, using the minimum inhibitory concentration (MIC) method, in compliance with guidelines from the Clinical and Laboratory Standards Institute (CLSI). Results: The hexanic extract caused significant inhibition from dilution 0.16 µg/mL for S. aureus strain ATCC 43300, and from dilution 19.5 µg/mL for strain ATCC 25923 (MSSA). The ethanolic and hexanic extracts significantly inhibited the growth of the clinical E. coli strain, whereas no significant inhibition was observed for K. pneumoniae at any of the concentrations tested. Conclusions: For the first time it was shown that the total hexanic extract of leaves of C. moschata had the greatest inhibition power against clinical strains of S. aureus and E. coli. The antimicrobial potential of this native species from the Colombian Caribbean has been recognized, and it is recommended to conduct assays with a larger number of human pathogens(AU)

Introducción: Cucurbita moschata Duchesne (Ahuyama) es cultivada en toda América, así como en Medio Oriente y Europa. Es utilizada desde la antigüedad como medicina alternativa. En la zona norte del departamento de Bolívar-Colombia es empleada por los campesinos para tratar infecciones en la piel, lo que generó el interés por desarrollar esta investigación. Objetivo: evaluar la actividad antibacteriana del extracto total de hojas de C. moschata frente a Staphylococcus aureus, Klebsiella pneumoniae y Escherichia coli. Métodos: hojas frescas de C. moschata fueron clasificadas taxonómicamente de acuerdo a métodos estándares. La obtención de los extractos se realizó por secado en horno, pulverización en molino de cuchilla, extracción por percolación sólido-líquido en frío y concentración en evaporador rotatorio. La actividad antibacteriana de los extractos etanólicos y hexánicos se evaluó in vitro frente a Staphylococcus aureus meticilino resistente, Escherichia coli y Klebsiella pneumoniae, mediante el método de Concentración Inhibitoria Mínima (CIM), siguiendo los lineamientos establecidos por Clinical and Laboratory Standards Institute (CLSI). Resultados: el extracto hexánico generó inhibición significativa desde la dilución 0,16 µg/mL para la cepa de S. aureus ATCC 43300. Para la cepa ATCC 25923 (MSSA) el extracto hexánico generó inhibición significativa desde la dilución 19,5 µg/mL. Los extractos etanólico y hexánico inhibieron significativamente el crecimiento de la cepa clínica de E. coli., mientras que para K. pneumoniae no hubo inhibición significativa en ninguna de las concentraciones evaluadas. Conclusiones: se demostró por primera vez que el extracto hexánico total de hojas de C. moschata tuvo el mayor poder de inhibición frente a las cepas clínicas de S. aureus y E. coli. Se reconoce el potencial antimicrobiano de esta especie autóctona de la costa del Caribe colombiano y se recomienda realizar ensayos en un número mayor de patógenos humanos(AU)

Scanning ion-selective electrode technique and X-ray microanalysis provide direct evidence of contrasting Na+ transport ability from root to shoot in salt-sensitive cucumber and salt-tolerant pumpkin under NaCl stress.

Grafting onto salt-tolerant pumpkin rootstock can increase cucumber salt tolerance. Previous studies have suggested that this can be attributed to pumpkin roots with higher capacity to limit the transport of Na(+) to the shoot than cucumber roots. However, the mechanism remains unclear. This study investigated the transport of Na(+) in salt-tolerant pumpkin and salt-sensitive cucumber plants under high (200 mM) or moderate (90 mM) NaCl stress. Scanning ion-selective electrode technique showed that pumpkin roots exhibited a higher capacity to extrude Na(+), and a correspondingly increased H(+) influx under 200 or 90 mM NaCl stress. The 200 mM NaCl induced Na(+)/H(+) exchange in the root was inhibited by amiloride (a Na(+)/H(+) antiporter inhibitor) or vanadate [a plasma membrane (PM) H(+) -ATPase inhibitor], indicating that Na(+) exclusion in salt stressed pumpkin and cucumber roots was the result of an active Na(+)/H(+) antiporter across the PM, and the Na(+)/H(+) antiporter system in salt stressed pumpkin roots was sufficient to exclude Na(+) X-ray microanalysis showed higher Na(+) in the cortex, but lower Na(+) in the stele of pumpkin roots than that in cucumber roots under 90 mM NaCl stress, suggesting that the highly vacuolated root cortical cells of pumpkin roots could sequester more Na(+), limit the radial transport of Na(+) to the stele and thus restrict the transport of Na(+) to the shoot. These results provide direct evidence for pumpkin roots with higher capacity to limit the transport of Na(+) to the shoot than cucumber roots.

Cadmium induced changes in subcellular glutathione contents within glandular trichomes of Cucurbita pepo L.

Plants cope with cadmium (Cd) stress by complexation with phytochelatins (Pc), metallothioneins and glutathione and sequestration within vacuoles. Especially glutathione was found to play a major role in Cd detoxification as Cd shows a high binding affinity towards thiols and as glutathione is a precursor for Pc synthesis. In the present study, we have used an immunohistochemical approach combined with computer-supported transmission electron microscopy in order to measure changes in the subcellular distribution of glutathione during Cd-stress in mesophyll cells and cells of different glandular trichomes (long and short stalked) of Cucurbita pepo L. subsp. pepo var. styriaca GREB: . Even though no ultrastructural alterations were observed in leaf and glandular trichome cells after the treatment of plants with 50 microM cadmium chloride (CdCl(2)) for 48 h, all cells showed a large decrease in glutathione contents. The strongest decrease was found in nuclei and the cytosol (up to 76%) in glandular trichomes which are considered as a major side of Cd accumulation in leaves. The ratio of glutathione between the cytosol and nuclei and the other cell compartments was strongly decreased only in glandular trichomes (more than 50%) indicating that glutathione in these two cell compartments is especially important for the detoxification of Cd in glandular trichomes. Additionally, these data indicate that large amounts of Cd are withdrawn from nuclei during Cd exposure. The present study gives a detailed insight into the compartment-specific importance of glutathione during Cd exposure in mesophyll cells and glandular trichomes of C. pepo L. plants.

Uptake, translocation, and accumulation of manufactured iron oxide nanoparticles by pumpkin plants.

Rapid development and application of nanomaterials and nanotechnology make assessment of their potential health and environmental impacts on humans, non-human biota, and ecosystems imperative. Here we show that pumpkin plants (Cucurbita maxima), grown in an aqueous medium containing magnetite (Fe3O4) nanoparticles, can absorb, translocate, and accumulate the particles in the plant tissues. These results suggest that plants, as an important component of the environmental and ecological systems, need to be included when evaluating the overall fate, transport and exposure pathways of nanoparticles in the environment.

Physiological and metabolic changes of Cucurbita pepo leaves in response to zucchini yellow mosaic virus (ZYMV) infection and salicylic acid treatments.

The changes of some physiological and biochemical parameters in pumpkin (Cucurbita pepo cv Eskandarani) leaves associated with zucchini yellow mosaic virus (ZYMV) infection and the effect of exogenous application of salicylic acid (SA) were studied in this paper. In comparison to the untreated leaves, ZYMV infected leaves showed many symptoms, including severe mosaic, size reduction, stunting and deformation. Results from analysis of physiological parameters indicated that viral infection and SA treatments affected metabolism. Viral infection decreased pigment, protein and carbohydrate levels. But with all SA treatments, the protein and carbohydrate contents are noticeably increased. Moreover, the other biochemical parameters showed variable alterations. The peroxidase (POX, EC 1.11.1.7) activity and proline contents were induced by both viral infection and SA treatments. In addition, protein patterns represent some newly synthesized polypeptides which reflect formation of pathogenesis related proteins in all treatments. SA treatment increases the plant resistance against ZYMV. This can be noticed through reduction of percentage of the infected plants, decrease in disease severity and virus concentration of the plants treated with SA then inoculated with virus. All results show significant changes in metabolism affected by either viral infection or SA treatments and also indicate that exogenous SA plays an important role in induction of defense mechanism against ZYMV infection.

Intracellular adaptations of glutathione content in Cucurbita pepo L. induced by treatment with reduced glutathione and buthionine sulfoximine.

The intracellular effects of GSH (reduced glutathione) and BSO (buthionine sulfoximine) treatment on glutathione content were investigated with immunogold labeling in individual cellular compartments of Cucurbita pepo L. seedlings. Generally, GSH treatment led to increased levels of glutathione in roots and leaves (up to 3.5-fold in nuclei), whereas BSO treatment significantly decreased glutathione content in all organs. Transmission electron microscopy revealed that glutathione levels in mitochondria, which showed the highest glutathione labeling density of all compartments, remained generally unaffected by both treatments. Since glutathione within mitochondria is involved in the regulation of cell death, these results indicate that high and stable levels of glutathione in mitochondria play an important role in cell survival strategies. BSO treatment significantly decreased glutathione levels (1) in roots by about 78% in plastids and 60.8% in the cytosol and (2) in cotyledons by about 55% in the cytosol and 38.6% in plastids. After a short recovery period, glutathione levels were significantly increased in plastids and the cytosol of root tip cells (up to 3.7-fold) and back to control values in cotyledons. These results indicate that plastids, either alone or together with the cytosol, are the main center of glutathione synthesis in leaves as well as in roots. After GSH treatment for 24 h, severe ultrastructural damage related to increased levels of glutathione was found in roots, in all organelles except mitochondria. Possible negative effects of GSH treatment leading to the observed ultrastructural damage are discussed.

Salicylic acid-induced resistance to Cucumber mosaic virus in squash and Arabidopsis thaliana: contrasting mechanisms of induction and antiviral action.

Salicylic acid (SA)-induced resistance to Cucumber mosaic virus (CMV) in tobacco (Nicotiana tabacum) results from inhibition of systemic virus movement and is induced via a signal transduction pathway that also can be triggered by antimycin A, an inducer of the mitochondrial enzyme alternative oxidase (AOX). In Arabidopsis thaliana, inhibition of CMV systemic movement also is induced by SA and antimycin A. These results indicate that the mechanisms underlying induced resistance to CMV in tobacco and A. thaliana are very similar. In contrast to the situation in tobacco and A. thaliana, in squash (Cucurbita pepo), SA-induced resistance to CMV results from inhibited virus accumulation in directly inoculated tissue, most likely through inhibition of cell-to-cell movement. Furthermore, neither of the AOX inducers antimycin A or KCN induced resistance to CMV in squash. Additionally, AOX inhibitors that compromise SA-induced resistance to CMV in tobacco did not inhibit SA-induced resistance to the virus in squash. The results show that different host species may use significantly different approaches to resist infection by the same virus. These findings also imply that caution is required when attempting to apply findings on plant-virus interactions from model systems to a wider range of host species.

Localization of ascorbic acid, ascorbic acid oxidase, and glutathione in roots of Cucurbita maxima L.

To understand the function of ascorbic acid (ASC) in root development, the distribution of ASC, ASC oxidase, and glutathione (GSH) were investigated in cells and tissues of the root apex of Cucubita maxima. ASC was regularly distributed in the cytosol of almost all root cells, with the exception of quiescent centre (QC) cells. ASC also occurred at the surface of the nuclear membrane and correspondingly in the nucleoli. No ASC could be observed in vacuoles. ASC oxidase was detected by immunolocalization mainly in cell walls and vacuoles. This enzyme was particularly abundant in the QC and in differentiating vascular tissues and was absent in lateral root primordia. Administration of the ASC precursor L-galactono-gamma-lactone markedly increased ASC content in all root cells, including the QC. Root treatment with the ASC oxidized product, dehydroascorbic acid (DHA), also increased ASC content, but caused ASC accumulation only in peripheral tissues, where DHA was apparently reduced at the expense of GSH. The different pattern of distribution of ASC in different tissues and cell compartments reflects its possible role in cell metabolism and root morphogenesis.

Aluminium-induced growth inhibition is associated with impaired efflux and influx of H+ across the plasma membrane in root apices of squash (Cucurbita pepo).

It is generally understood that the inhibition of growth of root apices is the initial effect caused by aluminium (Al) toxicity. The correlation between impaired H+-fluxes across the plasma membrane (PM) and Al-induced growth inhibition, Al accumulation and callose formation in root apices of squash (Cucurbita pepo L. cv. Tetsukabuto) is reported here. The root inhibition was dependent on Al concentration, and the duration of exposure, with the damage occurring preferentially in regions with high Al accumulation and callose formation. Using the fluorescent Al indicator (Morin), Al was localized in the cell walls of the root-tip cells after 3 h and in the whole root-tip cells after 6 h of the Al treatment (50 micro M). The inhibition of H+-pumping rate in the highly purified PM vesicles obtained from the Al-treated apical root portions (1 cm) coincided with the inhibition of root growth under Al stress. Furthermore, H+-ATPase activity of PM vesicles prepared from the control root apices was strongly inhibited by Al in vitro in a dose-dependent manner. Approximately 50% inhibition was observed when PM vesicles were preincubated at Al concentration as low as 10 micro M followed by the enzyme assay in the medium without Al. Using the pH indicator (bromocresol purple), it is shown that surface pH of the control (0 Al) root apices was strongly alkalized from the starting pH of 4.5 in a time-dependent manner. By contrast, the surface pH changed only slightly in the Al-treated root apices. The changes in surface pH mediated by altered dynamics of H+ efflux and influx across the root tip PM play an important role in root growth as affected by Al.