Yvonne Ventura

The development of halophyte-based agriculture: past and present

BACKGROUND Freshwater comprises about a mere 2·5% of total global water, of which approximately two-thirds is locked into glaciers at the polar ice caps and on mountains. In conjunction with this, in many instances irrigation with freshwater causes an increase in soil salinity due to overirrigation of agricultural land, inefficient water use and poor drainage of unsuitable soils. The problem of salinity was recognized a long time ago and, due to the importance of irrigated agriculture, numerous efforts have been devoted towards improving crop species for better utilization of saline soils and water. Irrigating plants with saline water is a challenge for practitioners and researchers throughout the world. SCOPE Recruiting wild halophytes with economic potential was suggested several decades ago as a way to reduce the damage caused by salinization of soil and water. A range of cultivation systems for the utilization of halophytes have been developed, for the production of biofuel, purification of saline effluent in constructed wetlands, landscaping, cultivation of gourmet vegetables, and more. This review critically analyses past and present halophyte-based production systems in the context of genetics, physiology, agrotechnical issues and product value. There are still difficulties that need to be overcome, such as direct germination in saline conditions or genotype selection. However, more and more research is being directed not only towards determining salt tolerance of halophytes, but also to the improvement of agricultural traits for long-term progress.

Life is three dimensional-as in vitro cancer cultures should be.

For many decades, fundamental cancer research has relied on two-dimensional in vitro cell culture models. However, these provide a poor representation of the complex three-dimensional (3D) architecture of living tissues. The more recent 3D culture systems, which range from ridged scaffolds to semiliquid gels, resemble their natural counterparts more closely. The arrangement of the cells in 3D systems allows better cell-cell interaction and facilitates extracellular matrix secretion, with concomitant effects on gene and protein expression and cellular behavior. Many studies have reported differences between 3D and 2D systems as regards responses to therapeutic agents and pivotal cellular processes such as cell differentiation, morphology, and signaling pathways, demonstrating the importance of 3D culturing for various cancer cell lines.

Impairment in Sulfite Reductase Leads to Early Leaf Senescence in Tomato Plants

Insufficient sulfite reductase activity activates the upstream components of the sulfate reduction pathway in tomato plants, resulting in accumulation of toxic sulfite and early leaf senescence. Sulfite reductase (SiR) is an essential enzyme of the sulfate assimilation reductive pathway, which catalyzes the reduction of sulfite to sulfide. Here, we show that tomato (Solanum lycopersicum) plants with impaired SiR expression due to RNA interference (SIR Ri) developed early leaf senescence. The visual chlorophyll degradation in leaves of SIR Ri mutants was accompanied by a reduction of maximal quantum yield, as well as accumulation of hydrogen peroxide and malondialdehyde, a product of lipid peroxidation. Interestingly, messenger RNA transcripts and proteins involved in chlorophyll breakdown in the chloroplasts were found to be enhanced in the mutants, while transcripts and their plastidic proteins, functioning in photosystem II, were reduced in these mutants compared with wild-type leaves. As a consequence of SiR impairment, the levels of sulfite, sulfate, and thiosulfate were higher and glutathione levels were lower compared with the wild type. Unexpectedly, in a futile attempt to compensate for the low glutathione, the activity of adenosine-5′-phosphosulfate reductase was enhanced, leading to further sulfite accumulation in SIR Ri plants. Increased sulfite oxidation to sulfate and incorporation of sulfite into sulfoquinovosyl diacylglycerols were not sufficient to maintain low basal sulfite levels, resulting in accumulative leaf damage in mutant leaves. Our results indicate that, in addition to its biosynthetic role, SiR plays an important role in prevention of premature senescence. The higher sulfite is likely the main reason for the initiation of chlorophyll degradation, while the lower glutathione as well as the higher hydrogen peroxide and malondialdehyde additionally contribute to premature senescence in mutant leaves.

The importance of iron supply during repetitive harvesting of Aster tripolium

Aster tripolium L. is a salt marsh halophyte that has recently gained interest as a cash crop vegetable. Leaf yield and quality were investigated in plants grown with salinity in experiments with Perlite in pots and in plots on dune sand. Plants were repetitively harvested in a 14-day cycle. A. tripolium irrigated with 50mM NaCl exhibited the highest yield when grown in pots, whereas in the plot experiment no significant differences in biomass accumulation occurred up to 80mM NaCl in the irrigation water. Chemical leaf composition changed with salinity, exhibiting higher levels of electrical conductivity, total soluble solutes and the non-enzymatic antioxidant compounds ascorbic acid and polyphenols compared with control plants grown without NaCl supplementation. Using the repetitive harvest regime, leaf chlorosis occurred, a symptom shared by deficiencies in either nitrogen or iron. Comparative applications of five iron chelate formulations in plants grown with 50mM NaCl in pots revealed improved leaf colour and chlorophyll content for only two of the applied Fe-chelates. Concomitantly with leaf colour restoration, the activity of nitrate reductase, the first enzyme during nitrate assimilation, which requires heme-iron for its proper function, increased 3-fold as a result of the iron treatment in the plot experiment. Importantly, the enhancement of nitrate reductase activity was associated with a considerable decrease in the leaf nitrate concentration. Therefore, we concluded that iron deficiency, in addition to leaf chlorosis, reduces A. tripolium leaf quality as a vegetable by increasing the leaf nitrate content. Furthermore, nitrate reductase (NR) activity levels in A. tripolium leaves may act as an indicator of iron deficiency that manifests itself as reduced nitrate content owing to the higher NR activity upon proper iron nutrition. These results demonstrate the importance of salinity level and the application of an appropriate iron-chelating formulation to generate marketable yields of Aster tripolium leafy vegetable when grown commercially on dune sand.

EFFECTS OF SUBOPTIMAL LOW TEMPERATURE ON YIELD, FRUIT APPEARANCE AND QUALITY IN MUSKMELON (CUCUMIS MELO L.) CULTIVARS

SummaryThe effects of suboptimal low temperature were investigated on an array of yield, fruit appearance and fruit quality characters in 23 cultivars of melon, Cucumis melo L. The cultivars were grown in two temperature regimes: (I) a heated greenhouse (T1) with temperatures similar to those used in commercial cultivation in the winter in Israel; and (ii) an unheated greenhouse (T2) that had significantly lower night temperatures than T1. Significant differences were found among the cultivars in all characters. Plants from T2 showed an extended fruiting period, more fruits and higher total yield but smaller and lighter fruits than in T1. Fruits from T2 also had significantly more netting and higher amounts of total soluble sugars (TSS), sucrose and fructose than fruits from T1. Hybrid cultivars showed significantly higher electrical conductivity (EC), pH, acidity, TSS, sucrose, fructose and total sugars than open pollinated cultivars. Three trends were found among the characters in respect to the perform...

A Novel In-gel Assay and an Improved Kinetic Assay for Determining In Vitro Sulfite Reductase Activity in Plants

Sulfite reductase (SiR; EC 1.8.7.1), an essential enzyme in the sulfate reduction pathway, catalyzes the reduction of sulfite to sulfide, as an intermediate for cysteine biosynthesis. The commonly used kinetic assay for the detection of in vitro SiR activity in plants is based on a coupled reaction, in which the sulfide produced is converted to cysteine through the presence, in the assay medium, of O-acetylserine sulfhydralase (EC 2.5.1.47) and its substrate, O-acetylserine. An improved kinetic assay for SiR activity in crude desalted protein extracts was developed. The improvement was based on pre-treatment of the protein with tungstate, which improved SiR activity in Arabidopsis and tomato leaf by 29 and 12%, respectively, and the addition of NADPH to the reaction medium, which increased SiR activity by 1.6- and 2.8-fold in Arabidopsis and tomato, respectively, in comparison with the current protocols. Despite the availability and reliability of the kinetic assay, there is currently no assay that enables the direct detection of SiR in relatively large numbers of samples. To meet this need, we developed a novel in-gel assay to detect SiR activity in crude extracts. The method is based on the detection of a brownish-black precipitated band of lead sulfide, formed by the reaction of lead acetate with sulfide. The in-gel assay for SiR activity is reliable, sensitive and technically simpler than the kinetic assay, and opens up the possibility for detecting active SiR isoenzymes and splice variants.

Effects of salinity on flowering, morphology, biomass accumulation and leaf metabolites in an edible halophyte

Cultivating crops under saline conditions is of high importance due to global fresh water shortage for irrigation. Crithmum maritimum is a halophytic plant that has a long history of human consumption and was suggested as a cash crop for biosaline agriculture. Our results highlight variations existing among Crithmum maritimum genotypes from different geographic origins regarding salt-induced changes in plant growth, flowering behavior and leaf metabolites with nutritional value. Our results indicate that genotypic characteristics should be taken into account when evaluating wild plant species for future crop cultivation.

The effect of pH and calcium ions on the stability of amphiphilic and anionic β‐sheet peptide hydrogels

Amphiphilic peptides can form bottom-up-designed self-assembled hydrogels composed of elongated fibril matrices that could find uses in various biologically-related systems, acting as platforms for drug delivery or scaffolds that mimic extracellular matrices in tissue regeneration systems. We have previously reported that the amphiphilic and anionic β-sheet forming peptide, Pro-Asp-(Phe-Asp)5 -Pro, P(FD)-5, generates hydrogels that template calcium-phosphate mineral and as such, were able to enhance bone formation in vivo. Our earlier results prompted us to further exploit the effects of pH and calcium ion concentration on P(FD)-5 peptide in solution, in hydrogels and in mineral-loaded hydrogel compositions. Circular dichroism-based characterization of solutions of the peptide demonstrated transitions between the unfolded state to a β-sheet structure as function of peptide concentration, pH and calcium ion concentration. FTIR measurements were employed to monitor differences between the structure of the peptide in solution and in hydrogels. Rheology and dissolution studies demonstrated the improved stability of hydrogels prepared by a two-step procedure, where the peptides are dissolved and self-assemble in the first step, while in the second step, calcium ions are allowed to adsorb onto the system. These results, highlighting the effects of a few central factors on the structure, assembly and stability of amphiphilic and anionic β-sheet peptide systems, will contribute to the further development of designed self-assembled peptide systems from solutions to hydrogels and hydrogel-loaded matrices, such as mineral putty compositions.

Cytotoxic characteristics of biodegradable EW10X04 Mg alloy after Nd coating and subsequent heat treatment.

Porous Mg scaffolds are considered as potential bone growth promoting materials. Unfortunately, the high rate of biocorrosion inherent to Mg alloys may cause a premature loss of mechanical strength, excessive evolution of hydrogen gas, and a rapidly shifting surface topography, all of which may hinder the ability of native cells to attach and grow on the implant surface. Here we investigated the cell cytotoxicity effects during corrosion of a novel magnesium alloy, EW10X04 (Mg-1.2%Nd-0.5%Y-0.5%Zr-0.4%Ca), following diffusion coating (DC) and heat treatment to reduce the corrosion rate. Cells were exposed either to corrosion products or to the corroding scaffold surface, in vitro. The microstructure characterization of the scaffold surface was carried out by scanning electron microscopy (SEM) equipped with a Noran energy dispersive spectrometer (EDS). Phase analyses were obtained by X-ray diffraction (XRD). We found that cell viability, growth, and adhesion were all improved when cultured on the EW10X04+DC surface or under corrosion product extracts due to lower corrosion rates relative to the EW10X04 control samples. It is therefore believed that the tested alloy after Nd coating and heat treatment may introduce a good balance between its biodegradation characteristics and cytotoxic effects towards cells.

Mycorrhized Ri-transformed roots facilitate in vitro inoculation of Cistus incanus with Tuber melanosporum

Progress was made towards a reliable in vitro system for mycorrhizing Cistus incanus seedlings with Tuber melanosporum. A rich growth medium favored extensive growth of mycorrhized Ri-transformed roots (MTR) but inhibited mycelial outgrowth into the medium. A minimal medium, on the other hand, inhibited MTR growth but supported considerable mycelial outgrowth into the medium. While the presence of a C.␣incanus propagule clearly enhanced mycelial growth into the minimal medium, a highly significant factor appeared to be the use of MTR inoculant, which supported mycorrhizal development to the Hartig net stage. The advantages of MTR for in vitro mycorrhization of host plant seedlings are discussed.