Search

Prosopis strombulifera (Lam.) Benth. is a halophytic shrub abundant in high-salinity areas in central Argentina, with high tolerance against NaCl but strong growth inhibition by Na2SO4. In the present study, the modulation of the antioxidant systems (enzymatic and non-enzymatic components) was analyzed under different salt treatments (NaCl, Na2SO4 and the iso-osmotic mixture) in hydroponic cultivation. Na2SO4-treated plants showed strong indications of oxidative stress (H2O2 and O2-• increase). Modifications in antioxidant enzymes activities were observed mainly under Na2SO4 treatment, where CAT seems to play an important role in early detoxification of H2O2 in roots, whereas SOD and APX have a predominant role in leaves. As part of the non-enzymatic system, 21 compounds were identified in leaves, being polyphenols the most abundant. Control plants contained the major variety of detected phytochemicals (14). Na2SO4-treated plants contained 10 compounds and NaCl-treated plants nine compounds, but with a different profile. NaCl-treated plants showed the highest antioxidant capacity. Our findings confirm that different types of salt treatments provoke a differential modulation of the antioxidant systems. Polyphenols and other ROS-detoxifying compounds, in a joint action with the enzymatic antioxidant system, are proposed to have a fundamental role in the cellular protection of P. strombulifera plants under severe oxidative stress. Our findings also highlight the potential of this halophyte as a valuable source of bioactive compounds with high antioxidant activity and health benefits.

In some areas of the world, high levels of sodium sulfate (Na2SO4) are found in the soil together with sodium chloride (NaCl). However, most studies on salinity are performed utilizing only NaCl as a salinizing agent. Generally, plant species have different tolerance/susceptibility responses when grown in the presence of these salts. Some studies showed that Na2SO4 seems to be more inhibitory than NaCl for the growth of species such as barley, wheat, sugar cane, beet, tomato, wild potato, and others. However, studies focusing on how Na2SO4 can affect the biochemical and physiological processes of plants are very scarce. This review provides an overview on the effects of Na2SO4 on different crops and plants species with a special emphasis on the tolerance/non-tolerance mechanisms of the halophyte Prosopis strombulifera under elevated NaCl and Na2SO4. A better understanding of the tolerance mechanisms in this particular species will help to identify cultivars of crop species that are more tolerant to Na2SO4. This knowledge could be used to extent cultivation of certain crop plants on Na2SO4 containing soils.

Prosopis strombulifera (Lam.) Benth. is a halophytic shrub found in highly saline soils in Argentina, with high tolerance against NaCl but strong growth inhibition by Na2SO4. In the present study, the differences in the physiological responses caused by these salts and an iso-osmotic combination thereof on photosynthesis, mineral composition and metabolism were analyzed. Na2SO4 treated plants were the most affected by salinity, showing a significant decrease in several photosynthetic parameters. Proline and cysteine accumulated significantly in the plants in response to salt stress. These results show by the first time that the SO42− anion is triggering damage in the photosynthetic apparatus and consequently affecting the photosynthetic process, which may explain the strong growth inhibition in these plants at high salinity. Moreover, the SO42− anion provoke challenges in the incorporation of nutrients, decreasing the levels of K, Ca, P and Mg, and inducing a strong antioxidant activity in P. strombulifera. Fil: Reginato, Mariana Andrea. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones Agrobiotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Agrobiotecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Botánica. Laboratorio de Fisiología Vegetal; Argentina Fil: Turcios, Ariel E.. Leibniz Universitat Hannover; Alemania Fil: Luna, Maria Virginia. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Botánica. Laboratorio de Fisiología Vegetal; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones Agrobiotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Agrobiotecnológicas; Argentina Fil: Papenbrock, Jutta. Leibniz Universitat Hannover; Alemania

The present study investigated the changes in total and individual glucosinolates (GSLs) in roots and leaves of different clubroot-resistant and -susceptible oilseed rape cultivars following artificial inoculation with Plasmodiophora brassicae isolates with different virulence. The results showed significant differences in clubroot incidence and severity as well as in the amount of total and individual glucosinolates between oilseed rape cultivars in response to virulence of the pathogen. Single among with total aliphatic and total indolic glucosinolate contents were significantly lower in leaves of susceptible cultivars compared to resistant ones due to the infection. Similarly, single and total aliphatic as well as indolic glucosinolate contents in roots were lower in susceptible cultivars compared to resistant cultivars analyzed. The different isolates of P. brassicae seem to differ in their ability to reduce gluconasturtiin contents in the host. The more aggressive isolate P1 (+) might be able to suppress gluconasturtiin synthesis of the host in a more pronounced manner compared to the isolate P1. A possible interaction of breakdown products of glucobrassicin with the auxin receptor transport inhibitor response 1 (TIR1) is hypothesized and its possible effects on auxin signaling in roots and leaves of resistant and susceptible cultivars is discussed. A potential interplay between aliphatic and indolic glucosinolates that might be involved in water homeostasis in resistant cultivars is explained. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Knowledge about Solanaceae species naturally adapted to salinity is scarce, despite the fact that a considerable number of Solanaceae has been reported growing in saline environments. Lycium humile Phil. inhabits extreme saline soils in the Altiplano-Puna region (Central Andes, South America) and represents a promising experimental model to study salt tolerance in Solanaceae plants. Seeds, leaves and roots were collected from a saline environment (Salar del Diablo, Argentina). Seeds were scarified and 30 days after germination salt treatments were applied by adding NaCl salt pulses (up to 750 or 1000 mM). Different growth parameters were evaluated, and leaf spectral reflectance, endogenous phytohormone levels, antioxidant capacity, proline and elemental content, and morpho-anatomical characteristics in L. humile under salinity were analyzed both in controlled and natural conditions. The multiple salt tolerance mechanisms found in this species are mainly the accumulation of the phytohormone abscisic acid, the increase of the antioxidant capacity and proline content, together with the development of a large leaf water-storage parenchyma that allows Na+ accumulation and an efficient osmotic adjustment. Lycium humile is probably one of the most salt-tolerant Solanaceae species in the world, and, in controlled conditions, can effectively grow at high NaCl concentrations (at least, up to 750 mM NaCl) but also, in the absence of salts in the medium. Therefore, we propose that natural distribution of L. humile is more related to water availability, as a limiting factor of growth in Altiplano-Puna saline habitats, than to high salt concentrations in the soils.

Mangroves are able to withstand a number of stress factors, such as high salt concentrations, tidal flooding, strong wind, solar radiation and heat. Their ability to grow under these circumstances is based on morphological and physiological adaptations, among them the high abundance of plant secondary metabolites. We are interested to investigate and exploit their medicinal and biotechnological potential for new bioactive compounds, without collecting material in the countries of origin and in a sustainable way. Therefore, a simple identification system based on molecular marker analysis, and a sustainable greenhouse propagation protocol for the continuous supply of fresh plant material, were established. DNA barcoding of the internal transcribed spacer (ITS) including ITS1, the 5.8S rRNA region and ITS2 as a molecular marker was applied for several mangrove species. The obtained data and GenBank sequences were used for species identification. Three mangrove species are cultivated in our greenhouse and propagated in different ways: Avicennia species produced many propagules in the greenhouse, however, further propagation by cuttings was not successful. Laguncularia racemosa was propagated by cuttings in a fog house whereas Bruguiera cylindrica was difficult to cultivate and propagation was not successful. Finally, the concentration of secondary phenolic compounds, including flavonoids, and the content of major elements were compared among naturally and greenhouse-grown mangroves indicating comparable amounts and composition.

The genusHalophilashows the highest species diversity within the seagrass genera. Southeast Asian countries where several boundary lines exist were considered as the origin of seagrasses. We hypothesize that the boundary lines, such as Wallace’s and Lydekker’s Lines, may act as marine geographic barriers to the population structure ofHalophila major. Seagrass samples were collected at three islands in Vietnamese waters and analyzed by the molecular maker ITS. These sequences were compared with published ITS sequences from seagrasses collected in the whole region of interest. In this study, we reveal the haplotype and nucleotide diversity, linking population genetics, phylogeography, phylogenetics and estimation of relative divergence times ofH.majorand other members of theHalophilagenus. The morphological characters show variation. The results of the ITS marker analysis reveal smaller groups ofH.majorfrom Myanmar, Shoalwater Bay (Australia) and Okinawa (Japan) with high supporting values. The remaining groups including Sri Lanka, Viet Nam, the Philippines, Thailand, Malaysia, Indonesia, Two Peoples Bay (Australia) and Tokushima (Japan) showed low supporting values. The Wallacea region shows the highest haplotype and also nucleotide diversity. Non-significant differences were found among regions, but significant differences were presented among populations. The relative divergence times between some members of sectionHalophilawere estimated 2.15–6.64 Mya.

The tropical seagrass Enhalus acoroides is considered as a potential bioindicator for heavy metals. To date, studies on the accumulation of heavy metals in each specific seagrass organ have been limited. In this study, surface sediment and E. acoroides samples collected at six distinct beds from the coast of Khanh Hoa province, Vietnam, were evaluated for their heavy metal concentrations (Cd, Cu, Pb and Zn) to determine which organs of E. acoroides could be used as bioindicators for heavy metals. The metal concentrations in both the sediment and the seagrass organs were measured using inductively coupled plasma mass spectrometry (ICP-MS). Bio-concentration factor ( BCF ) and Metal pollution index ( MPI ) were determined on the seagrass organs, and Pearson's correlation and ANOVA were used for statistical analysis. The results showed that the highest BCF values of Cd and Zn were found in leaves, the highest BCF value of Cu was found in the rhizomes and the highest BCF value of Pb was found in the roots. Generally, MPI was lower in the sediment than in seagrass organs at the same locations. For Cd, Pearson's correlation showed that a significant positive correlation was only observed between sediment and leaves with respect to BCF . A significant positive correlation of BCF for Cu was observed between sediment and rhizome while significant positive correlations of BCF for Cu, Pb and Zn were observed between sediment and roots. Based on the results, it can be concluded that E. acoroides leaves should be used as a bioindicator for Cd and Zn, rhizomes for Cu, and roots for the three metals Cu, Pb and Zn.

Seagrasses beds are vulnerable ecosystems. Human-induced disturbances, including heavy metal pollution, cause losses in seagrass beds. Assessment of the heavy metal concentration in seagrass meadows is an urgent need in order to protect and sustain these ecosystems. The concentration of eight trace metals in the surface sediment was observed from six seagrass beds at Khanh Hoa's coast, Vietnam. Three pollution indices and statistical analysis were used to evaluate the levels of contamination with these elements. This report on heavy metals within seagrass beds in Vietnam shows that, based on enrichment factors, only one location revealed moderately severe enrichment of Cu. Geo-accumulation indices fall in the uncontaminated class at all locations whereas for the ecological risk factor, values of Cu at My Giang and of Pb at Thuy Trieu were in a moderate risk class. Hence, two of eight locations may be exposed to high Cu and Pb.

Adapting biological processes to an endogenous rhythm enables plants to cope with the daily changes in light and temperature in a more predictable way enhancing growth and fitness. A number of biological processes such as metabolic pathways as well as the immunity in plants are under diurnal or circadian control. In this study a possible circadian regulation of key enzymes in the sulfur assimilation and the corresponding metabolites was investigated in the agriculturally important crop plant oilseed rape (Brassica napus). Leaves of a commercially available cultivar were harvested in the course of a day under diurnal and under free-running conditions with constant light. Analyses in this study were focused on sulfur-containing metabolites and expression analysis of enzymes involved in sulfur assimilation. Expression analysis showed that the transcript levels of the sulfate transporters Sultr3;1 and Sultr4;2 as well as APR2 and APR3 oscillated diurnally. Results revealed a periodic rhythm of sulfur-containing metabolites such as glutathione, sulfate and certain glucosinolates in the course of a day which were only partly maintained under constant light. Therefore, we conclude that a diurnal rhythm and not the circadian clock regulates sulfur metabolism in plants.

Along with coral reefs and mangroves, seagrass meadows are being threatened globally Southeast Asia is considered within the area of seagrasses’ cradle of diversity. However, information on the current status of seagrass beds from Southern Viet Nam is limited due to lack of reliable data about seagrass species occurring in the Southeast Asian region. One factor is the difficulty of unambiguous species identification. For example, the leaf morphological characteristics of Halophila ovalis and closely related species are overlapping which leads to misidentifications. In this study, the latest satellite Landsat 8 OLI and SENTINEL-2B image analyses were applied to determine the distribution of seagrass beds in Southern Viet Nam. Detailed morphological and genetic marker analyses were used to determine and update the species composition. The present study together with literature reviews indicate that the total area of seagrass beds from Southern Viet Nam are 10,832.1 ha. 2562 ha (or 19.1%) of seagrass coverage has been lost. The seagrass beds at Phu Quoc Island are the largest with 7579 ha. The occurrence of Halophila major is updated for almost all off-shore islands and open-water areas.

Taxonomic challenges of seagrasses were met by using 18S ribosomal subunit of ribosomal deoxyribonucleic acid (18S rDNA) sequence data of 14 seagrass species from India and two temperate species from Germany. The phylogenetic trees presented are based on the 18S rDNA sequence analysis of 41 nucleotide sequences including sequences obtained in the present study as well as previously published sequences of freshwater and saltmarsh plants, and seagrasses for identifying the evolutionary lineage. The 18S rDNA data indicates independent origin of temperate and tropical seagrasses with the genus Halophila as the intermediate group for both the regions. Based on the complex morphological structures the Halophila group represents the basal form among seagrasses whereas Enhalus is considered to be the most recently originated seagrass species. In that context, the marine Hydrocharitaceae group of Enhalus, Thalassia and Halophila has been proposed to be separated into two groups such as Enhalus/Thalassia and Halophila subfamilies. Hence, the present systematic studies warrant a revised taxonomy for seagrasses, which better reflects the phylogenetic results obtained from molecular and conventional data.

The halophyte species Sea Aster (Tripolium pannonicum) was grown with different concentrations of artificial seawater. In a second experiment, T. pannonicum was cultivated with a nutrient solution containing different concentrations of NaCl. This halophyte biomass was used to determine the biogas production potential. According to the findings, it is possible to produce high yields of methane using biomass from halophytes cultivated in the presence of salt. Biogas and methane yield are influenced by the salt content of the plant tissue, however, high concentrations of salt in the anaerobic reactors itself inhibit the biogas and methane production. The highest methane yield is obtained using plant substrates grown at 22.5 g L−1 sea-salt with a value of 313 cm3 g−1 of VS. When treating T. pannonicum with different concentrations of NaCl, biogas and methane yields are highest when using plant substrates grown at 30 g L−1 to produce values of 554 cm3 g−1 of VS and 447 cm3 g−1 of VS, respectively. Other research was carried out to study the effect of sodium on the biogas and methane yields using substrate from T. pannonicum cultured under non-saline conditions and adding different amounts of NaCl to the anaerobic reactors. Adding NaCl to the reactors decreases the biogas and methane production but using a salt-adapted inoculum increases the biogas yield in comparison to the non-adapted inoculum.

Salt marsh ecosystems are extremely impacted by human activities whilst also acting as sinks of contaminants such as heavy metals. Halophytic plant species can survive and thrive in estuarine and coastal areas with higher salt conditions that are generally not favourable to most plants. Halophyte distribution and abundance clearly relate to anthropogenic pressure levels and thus the impact of heavy metals needs to be rapidly assessed and monitored in a fast-developing world. To assess and manage this impact the search for suitable and efficient biomarkers is of great importance, aiming to produce a clear picture of environmental quality. The present work aimed to evaluate the application of optical tools, like non-invasive chlorophyll a pulse amplitude modulated (PAM) fluorometry, in four halophytic species (Halimione portulacoides, Sarcocornia fruticosa, Spartina maritima and Spartina patens), from three salt marshes of the Tagus estuary with different degrees of contamination, to investigate biomarkers for inclusion in a Multivariate Photochemical Pressure Index (Multi-PPI) destined for ecological quality assessment. The application of this index allowed to distinguish between less (Alcochete) and more (Rosario and Seixal) heavy metal contaminated salt marshes. This was observed particularly for S. maritima, in which Multi-PPI was lower for the higher contaminated sites, albeit this pattern was similarly observed in S. patens and S. fruticosa. On the other hand, the Multi-PPI index for H. portulacoides, a phytoextractor species, increased with the contamination gradient along the three salt marshes, and therefore this strategy should be considered when applying this index. Therefore, since these species are well represented in the Mediterranean, the use of optical tools to generate an easy fast index will have a great impact on the future of transitional ecosystem pollution impact assessments as well as in ecotoxicology research.

Balanites aegyptiaca (Balanitaceae) is a drought-tolerant but salt-sensitive tree species distributed in the tropical and arid lands in Africa and Asia. The tree contains many secondary metabolites and a high percentage of oil in the kernels that can be used for biodiesel production. This study aimed to establish an in vitro propagation system of two B. aegyptiaca provenances (El-Kharga and Wadi El-Alaqi) from nodal and cotyledon explants. The explants were placed on Murashige and Skoog medium supplemented with different concentrations of 6-benzyladenine (BA) and thidiazuron (TDZ) for shoot induction. BA was significantly more effective in shoot induction from nodal explants and treatment with BA also resulted in higher regeneration rates of about 40–60 % of adventitious shoots on cotyledon explants, whereas on TDZ-containing medium slightly higher shoot numbers per explant but a negative effect on shoot length were recorded. Rooting was achieved in 40–60 % of the shoots on medium containing between 1.2 and 4.8 µM indole-3-butyric acid. Three different Agrobacterium tumefaciens strains (EHA105, GV3101, and LBA4404) harboring the plasmid pCAMBIA2301 containing the nptII marker and gus reporter genes were used to establish a transformation system in B. aegyptiaca. Strain GV3101 resulted in the highest survival rates and highest number of explants positive in the GUS assay. This selected A. tumefaciens strain was used to introduce pBinAR containing the sequence encoding ERD10 (early responsive to dehydration 10) to produce salt-tolerant B. aegyptiaca plants. The presence of the ERD10 and the nptII gene were detected by PCR in transformed B. aegyptiaca plants.

Taxonomists find some plant genera challenging because of the few morphological differences or unclear characters among closely related species, which leads to the misidentification of taxa. DNA barcoding is an approach to identify species by using short orthologous DNA sequences, known as ‘DNA barcodes’. Concatenated rbcL and matK sequences are considered DNA barcodes for seagrasses. However, these markers are not applicable to all members of seagrasses at the species level, especially within the genus Halophila. Our previous studies indicated that the internal transcribed spacer (ITS) showed higher species resolution than the concatenated rbcL and matK sequences in the case of Halophila ovalis and closely related species. In this study, 26 ITS, two rbcL and two matK consensus sequences from 18 seagrass taxa belonging to four families collected in India, Vietnam, Germany, Croatia and Egypt were processed. Molecular ITS analysis resolved five clades. The results also indicate that the Cymodoceaceae family...

The effects of opening the Suez Canal as a connection between the Red Sea and the Mediterranean Sea were reported for a number of marine species. However, the evolutionary origin of the seagrasses in the Red Sea and the linking population genetics of seagrasses between the Arabian Sea, the Gulf of Aden, the Red Sea and the Mediterranean Sea have not yet been investigated in detail. The invasion of Halophila stipulacea Asch. from the Red Sea into the Mediterranean Sea after the opening of the Suez Canal was already recorded. We hypothesize that Halophila ovalis populations in the Red Sea developed through long-term historical processes such as vicariant evolutionary diversification. Seagrass samples were collected along the Egyptian coastline of the Red Sea and analysed by the molecular marker ITS. The sequences were compared with published ITS sequences from seagrasses collected in the whole area of interest. In this study, we reveal the linking population genetics, phylogeography and phylogenetics of two dominant seagrass species, Halophila stipulacea and Halophila ovalis, among species collected in the Red Sea and worldwide. The results indicate that the Red Sea Halophila ovalis populations do not group to Halophila ovalis worldwide, and Halophila major, Halophila ovalis collected worldwide and Halophila ovalis collected at the Red Sea are sister clades. Hence, vicariant evolutionary diversification for Halophila ovalis may occur in the Red Sea.

The aim of the study was to investigate the feasibility of nutrient recycling from a marine recirculating aquaculture system (RAS) for fish (European sea bass, Dicentrarchus labrax L.) through three salt-tolerant, halophyte plant species, Tripolium pannonicum (Jacq.) Dobrocz., Plantago coronopus L., and Salicornia dolichostachya (Moss.). Halophytes, illuminated by sunlight and supplemented with artificial light, were maintained in hydroponic cultures integrated in a RAS water treatment system operating at 16 psu salinity. During a 35-day experiment, 248 fishes gained 5.6 kg of weight. Total plant biomass production reached 23 kg in 14 m2 hydroponic culture area. Gain of shoot biomass was 27, 18, and 60 g m−2 day−1 for T. pannonicum, P. coronopus, and S. dolichostachya, respectively. The plants retained 7 g phosphorus and 46 g nitrogen under the experimental conditions. This was equivalent to 9 % of the N and 10 % of the P introduced with the fish feed. The edible part of the harvested plant material was microbially safe and approved for human consumption. The coupling of production in a RAS–IMTA was tested as a feasible cascading production technology for sustainable aquaculture.

Salt-tolerant plants can be used as biofilters for nutrient-rich saline water such as aquaculture process water. Tripolium pannonicum (Jacq.) Dobrocz. was used to determine optimal culturing conditions for an efficient biofilter performance in terms of nutrient recycling by plant uptake. This performance was evaluated by taking different parameters into account, such as biomass production, plant nitrogen and phosphorus uptake as well as physiological parameters and decrease of nitrate-N and phosphate-P concentrations in the experimental fluid. Afterwards, additional plant species known as edible were studied to follow the idea of generating valuable co-products beside the use as biofilter. It was shown that a nitrate-N concentration of at least 10 mg l −1 is necessary for reasonable biomass production. A phosphate-P concentration of 0.3 mg l −1 is sufficient, but higher concentrations promote the uptake of phosphate-P. The addition of iron in chelated form is required for the growth of healthy plant biomass; the addition of manganese is beneficial but not implicitly necessary. Salt concentrations lower than seawater salinity promote biomass production and nutrient uptake. The use of a hydroponic culture system is more suitable than sand or expanded clay culture if controlled conditions and nutrient recycling are desired. The five weeks experiment to compare different halophyte species in 0.24 m 2 tanks with nine plants each resulted in above ground fresh weight of 185 to 398 g and total uptake of nitrogen and phosphorus of 0.6 to 2.1 g and 0.1 to 0.4 g, respectively. All tested species have potential to serve as biofilter and source for valuable co-products. A promising application is the growth of halophytic vegetable plants in marine aquaponic systems.

Highlights • Protein–protein interactions of sulfurtransferases (Strs) with thioredoxins (Trxs) have been shown. • We used bimolecular fluorescence complementation (BiFC) to analyze Trx–Str interactions from Arabidopsis thaliana. • Compartment- and partner-specific interactions could be observed in transformed protoplasts. • Replacement of cysteine residues in the redox-active site of Trxs abolished the interaction signal. • Biochemical assays support a specific interaction among Strs and certain Trxs., Sulfurtransferases (Strs) and thioredoxins (Trxs) are members of large protein families. Trxs are disulfide reductases and play an important role in redox-related cellular processes. They interact with a broad range of proteins. Strs catalyze the transfer of a sulfur atom from a suitable sulfur donor to nucleophilic sulfur acceptors in vitro, but the physiological roles of these enzymes are not well defined. Several studies in different organisms demonstrate protein–protein interactions of Strs with members of the Trx family. We are interested in investigating the specificity of the interaction between Str and Trx isoforms. In order to use the bimolecular fluorescence complementation (BiFC), several Str and Trx sequences from Arabidopsis thaliana were cloned into the pUC-SPYNE and pUC-SPYCE split-YFP vectors, respectively. Each couple of plasmids containing the sequences for the putative interaction partners were transformed into Arabidopsis protoplasts and screened using a confocal laser scanning microscope. Compartment- and partner-specific interactions could be observed in transformed protoplasts. Replacement of cysteine residues in the redox-active site of Trxs abolished the interaction signal. Therefore, the redox site is not only involved in the redox reaction but also responsible for the interaction with partner proteins. Biochemical assays support a specific interaction among Strs and certain Trxs. Based on the results obtained, the interaction of Strs and Trxs indicates a role of Strs in the maintenance of the cellular redox homeostasis.

A well-established population of Claviceps purpurea var. spartinae R.A. Duncan & J.F. White was found on the invasive common cord-grass Spartina anglica C.E. Hubbard at two localities on the German North Sea coast. Additionally, 25 populations of S. anglica with an average air-line distance of 50 km between them along the coastline, starting from the Netherlands via the German coastline up to Denmark, were investigated. All S. anglica populations were heavily infected with C. purpurea var. spartinae (lineage G3). Genetic characterization of the C. purpurea DNA using Amplified Fragment Length Polymorphism (AFLP) and Internal Transcribed Spacer (ITS) analysis clearly indicated that all populations collected at the Wadden Sea were grouped in the same epidemic clade. Comparisons with reference strains indicated that the isolates along the Wadden Sea belonged to the clade also found in Ireland and Wales. The ergot alkaloid pattern is very similar in all genotypes. Ergocristine, α-ergocryptine and their epimers were identified in the samples in high amounts comparable to average values in sclerotia found on rye. The sclerotia of C. purpurea var. spartinae are able to float on the water for several months and could thereby be distributed over large distances by seawater. The sclerotia found in the drift lines still contain the equally high contents of ergot alkaloids as those collected directly from the plants. Current data form the basis for risk assessments and predictions about further spreading of C. purpurea var. spartinae on S. anglica.

Euphorbia tirucalli, a member of Euphorbiaceae, is a drought and salt-tolerant species. It is distributed in subtropical and semi-arid parts of Africa and was brought to Asia and North America. The plant has succulent stems performing CAM metabolism and small non-succulent leaves performing C3 metabolism. Different genotypes of E. tirucalli showed different tolerance to drought stress, especially Morocco and Senegal genotypes. This difference has tempted us to investigate the difference in antioxidant stress mechanisms in stems as compared to leaves. Plants from both genotypes have been subjected to drought (10% Volumetric Water Content, VWC) for 8 weeks and the leaves and stems were investigated for their reactive oxygen species (ROS) and antioxidants levels. Shoots of Morocco genotype retained water more efficiently under drought compared to Senegal shoots. Although H2O2 accumulated in stems under drought compared to leaves, however, the stems have elevated levels of various non-enzymatic and enzymatic antioxidants. Stems of Morocco increased their levels of H2O2 more under drought compared to Senegal stems, and Morocco stems showed a higher increase in their non-enzymatic and enzymatic antioxidants under drought. Morocco stems are distinguished by increased ascorbate peroxidase (APX) and peroxidase (POX) activities, while in Senegal stems catalase (CAT) activity specifically increased under drought. Levels of H2O2 in leaves were higher as compared to stems even under control conditions; however, leaves did not show increased antioxidant enzymes levels under drought stress. This tendency to accumulate H2O2 could be used by E. tirucalli as strategy to kill and get rid of leaves under drought to reduce transpirational water loss. These differences in antioxidant systems of Morocco and Senegal genotypes could, at least partly, explain their differences in drought tolerance and may reflect evolutionary adaptations to different local native climates.

C2 photosynthesis operates by shuttling photorespiratory glycine (C2) from mesophyll (M) to bundle sheath (BS) cells, followed by decarboxylation and release of CO2 around RubisCO. C2 plants are characterized by low apparent photorespiration and enhanced refixation of photorespiratory CO2 and the C2 pathway is thought to represent an intermediate step for the evolution from C3 to C4 photosynthesis. Restriction of glycine decarboxylation to the BS cells is considered to be a prerequisite for C2 photosynthesis. In the C3 plant species Arabidopsis thaliana, a cis-element required for expression of the P-subunit of glycine decarboxylase (GDC—P) in M cells (termed the M-box) was previously identified in the promoter of A. thaliana glycine decarboxylase P-subunit 1 (AtGldp1). Consequently, the loss of this element restricted Gldp1 expression to the BS cells. To investigate conservation, Gldp promoter sequences from another C3 and two additional C2 Moricandia species were isolated by genome walking. In comparison to AtGldp1, the M-box was conserved in the promoter of C3 Moricandia moricandioides, but was not found in the promoters of M. nitens, M. suffruticosa, and M. arvensis, indicating the loss of the M-box from several C2 Moricandia species. The AtGldp1 M-box was further analyzed in detail using promoter::GUS fusions. Results show that interaction between two promoter regions containing predicted CAAT and GATA elements are required for expression of the GUS reporter in M cells and these elements including their spacing are conserved in the promoters of different members of the Brassicaceae.

In the search of new compounds with biofilm-inhibiting properties, mangroves with their richness of secondary metabolites can be a valuable resource. Crude methanolic leaf extracts from the mangrove Laguncularia racemosa enriched in phenolic substances cause a reduction in initial cell adhesion of Candida glabrata and Candida albicans, but not on Escherichia coli. LC/MS-guided fractionation of the phenolic compounds resulted in 19 fractions, of which ten were analyzed for their bioactivity against cell adhesion. Effects on cell adhesion and planktonic growth of Escherichia coli, Candida glabrata and Candida albicans were measured in 96-well microtiter plates in the presence of 0.2 mg ml-1 of the isolated fractions. Two fractions caused a reduction of cell adhesion of Candida albicans. These fractions containing bioactive compounds were analyzed by LC/MS and NMR spectroscopy. Casuarinin and digalloyl-hexahydroxydiphenoyl-glucose were identified in the active fractions, in addition to three signals of ellagitannins. These results indicate a specific mode of action of hydrolysable tannins against cell adhesion of Candida albicans, which needs to be further analyzed.

Among the seagrass species, Halophila ovalis, H. ovalis subsp. ramamurthiana, H. ovata, H. major and H. minor complex, leaf morphological characters overlap. Previously, plastic and nuclear sequences were successfully applied to resolve genetic variation among all the members within this genus. However, Halophila ovalis, H. ovalis subsp. ramamurthiana and the H. ovata complex have not yet been fully resolved. This leads to the hypothesis that the genetic differences of H. ovalis and H. ovata are not at the loci we were studying. In this study, AFLP analysis based on 49 demes of four Halophila ovalis, one H. ovalis subsp. ramamurthiana and two H. ovata populations collected along the coast of Tamil Nadu, India, were carried out to find the genetic distance within and among populations. Results from a band-based approach showed that H. ovalis and H. ovata are definitely clustered into two clades with 100% bootstrap value. Principal Coordinate Analysis (PCoA) clearly depicts the genetic relationship among th...

Seagrasses are marine angiosperms and adapted to aquatic life several times independently. In tropical as well as in temperate regions they play an important role in the coastal ecosystem. Classification according to morphology remains difficult due to very similar adaptations to the aquatic lifestyle and small simple flowers which are often not even formed. Especially the Halophila genus (Hydrocharitaceae) forms a complex group with an unresolved taxonomy due to overlapping morphological characters and high plasticity leading to many misidentifications. Hence, this led to the hypothesis that phylogenetic analysis on the molecular level may resolve taxonomic classification. The aim of this study is to identify and unambiguously characterize Halophila species collected in Viet Nam using tree- and character-based analysis of rbcL and matK sequences. Results obtained from molecular data and leaf morphology indicate that there are at least three species found in Viet Nam. Topologies based on single locus or combined datasets were similar but not equal. Analysis of rbcL sequences showed lowest species resolution when only Halophila beccarii Aschers was resolved at the Halophila complex. matK shows better resolution with respect to H. beccarii and H. decipiens Ostenfeld. Combined rbcL and matK consensus trees showed the highest species resolution when all species form three distinct clades representative for three difference species including H. beccarii, H. decipiens, and H. ovalis (R. Br.) Hook. f.

The seagrass Halophila major (Zoll.) Miquel is reported for the first time from Vietnam. It was found growing with other seagrass species nearshore, 4–6 m deep at Tre Island, Nha Trang Bay. Leaf morphology and phylogenetic analysis based on ribosomal internal transcribed spacer sequences confirmed the identification. There was very little sequence differentiation among samples of H. major collected in Vietnam and other countries in the Western Pacific region. A very low evolutionary divergence among H. major populations was found.

The influence of salinity on the biosynthesis of secondary metabolites with a focus on single glucosinolates (GSLs) was investigated in Lepidium latifolium L., which is a plant species rich in antioxidants. Mature plants were subjected to 0, 15, 22.5, and 35 Practical Salinity Units (PSU) for 1–4 weeks. While phenols, flavonoids, and the oxygen radical absorbance capacity (ORAC) increased with increasing salinity, the ascorbate concentration did not follow a specific pattern. The concentration of single GSLs was influenced by salinity in different ways: While the concentration of aliphatic GSLs like glucoiberin and sinigrin increased, the concentration of aromatic GSLs such as glucobrassicin decreased under salinity stress. Salinity increased the total GSL concentration significantly with sinigrin being the major contributing GSL. The exact molecular role of the different GSLs in abiotic stress defense needs further analysis.

Phytochelatins (PCs), the heavy metal-binding peptides of plants, play a main function in heavy metal detoxification. In this study, Enhalus acoroides samples collected at six distinct seagrass beds from the coast of Khanh Hoa province, Viet Nam, were evaluated for their PCs. The contents of different PCs in each organ including leaf, rhizome, and root were determined by using HPLC analysis. Significant differences of PC2 contents among specific organs and their relation were tested by ANOVA, Tukey test, and Pearson's correlation. The results showed that higher PC2, appearance of PC3 and a strong correlation between PC2 and Pb concentration were found in the root organ collected from a Pb contaminated area. We conclude that high Pb in the sediment induce high PC2 and PC3 production in the root. This first report on in situ detection of PCs of seagrass encourages future investigation on the ability to use seagrass for phytoremediation and as a bioindicator of heavy metals based on PC contents.

This project analyses the uptake and biodegradation of the antimicrobial sulfadimidine (SDI) from the culture medium and up to the anaerobic digestion. Tripolium pannonicum was grown under hydroponic conditions with different concentrations of SDI (0, 5 and 10mg·L(-1)) and the fresh biomass, containing different amounts of SDI taken up, was used as substrate for biogas production. SDI was analyzed by liquid chromatography coupled to positive ion electrospray mass spectrometry (ESI LC-MS). Based on the findings, T. pannonicum is able to uptake SDI. The more SDI is in the culture medium, the higher the SDI content in the plant tissue. According to this study, it is possible to produce high yields of biogas using biomass of T. pannonicum containing SDI and at the same time biodegradation of SDI is carried out. The highest specific biogas yield is obtained using shoots as substrate of the plants cultivated at 5mg·L(-1) SDI.

Sulfurtransferases (Str) comprise a group of enzymes widely distributed in archaea, eubacteria, and eukaryota which catalyze the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors. Neither the in vivo sulfur donors nor the acceptors of Str could be clearly identified in any of the organisms investigated so far. In Oryza sativa L. 24 Str (OsStr) encoding genes have been identified and subdivided into six groups according to their sequence homology. To half of the Oryza Str a direct homolog and to 40% at least a similar protein in Arabidopsis thaliana (L.) Heynh. could be allocated. Only the group comprising two-domain Str contains more Oryza Str than Arabidopsis Str. According to EST abundance analysis most of the OsStr mRNAs accumulate in several plant tissues. OsStr22, the homolog to the best characterized Str1 from Arabidopsis (AtStr1), shows the highest expression in middle-aged plants whereas AtStr1 shows the highest expression in senescent plants. Heterologously expressed and purified OsStr22 shows very low enzyme activity in comparison to the Arabidopsis and the Brassica napus L. Str. The data obtained so far constitute the basis to analyze differences among the Str family from monocotyledonous and dicotyledonous plants.

Sulfotransferases (SOTs) (EC 2.8.2.-) catalyze the transfer of a sulfate group from the cosubstrate 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to a hydroxyl group of different substrates. In Arabidopsis thaliana, three SOTs were identified to catalyze the last step of glucosinolate (Gl) core structure biosynthesis called AtSOT16, 17 and 18. These enzymes from Arabidopsis ecotype C24 were overexpressed in Escherichia coli and purified by affinity chromatography. Recombinant proteins were used to determine substrate specificities to investigate whether each of the three desulfo (ds)-Gl SOTs might influence the Gl pattern of Arabidopsis differently. After optimization of the enzyme assay, it was possible to measure in vivo substrates with non-radioactive PAPS by HPLC analysis of the product. In vitro enzyme assays revealed a preference of AtSOT16 for the indolic ds-Gl indol-3-yl-methyl, AtSOT17 showed an increased specific activity with increasing chain length of ds-Gl derived from methionine and AtSOT18 preferred the long-chain ds-Gl, 7-methylthioheptyl and 8-methylthiooctyl, derived from methionine. In planta ds-Gl exist side by side; therefore, initial results from one substrate measurements were verified using a defined mixture of ds-Gl and ds-Gl/Gl leaf extracts from Arabidopsis ecotype C24. These studies confirmed the one substrate measurements. To compare SOTs from different Arabidopsis ecotypes, additionally, AtSOT18* from ecotype Col-0 was overexpressed in E. coli and purified. The recombinant protein was used for in vitro measurements and revealed a different enzymatical behavior compared with AtSOT18 from C24. In conclusion, there are differences in the substrate specificities between the three ds-Gl AtSOT proteins within ecotype C24 and differences among ds-Gl AtSOT18 proteins from different ecotypes.

In India 14 seagrass species can be found with monospecific genera (Enhalus, ThalassiaandSyringodium),Cymodoceawith two species andHalophilaandHalodulerepresented by more than two taxonomically complex species. Considering this, the present study was made to understand the level and pattern of genetic variability among these species collected from Tamilnadu coast, India. Random amplified polymorphic DNA (RAPD) analysis was used to evaluate the level of polymorphism existing between the species. Out of the 12 primers tested, 10 primers amplified 415 DNA fragments with an average of 41.5 fragments per primer. Of the total 415 amplified fragments only 123 (29.7%) were monomorphic and the remaining 292 (70.3%) were polymorphic for Indian seagrass species. Among the 10 primers used four are identified as the key primers capable of distinguishing all the Indian seagrasses with a high degree of polymorphism and bringing representative polymorphic alleles in all the tested seagrasses. From the present investigation, this study shows that the RAPD marker technique can be used not only as a tool to analyse genetic diversity but also to resolve the taxonomic uncertainties existing in the Indian seagrasses. The efficiency of these primers in bringing out the genetic polymorphism or homogeneity among different populations of theHalophilaandHalodulecomplex still has to be tested before recommending these primers as an identification tool for Indian seagrasses.

The sea aster, Aster tripolium L., grows naturally in temperate regions, mainly in the salt meadows close to the coast. The species is also found in naturally and anthropogenically salt-contaminated inland habitats, such as potash mine dumps. The genetic relationships among populations from different habitats and correlations of the genotype with physiological and vegetational parameters were investigated. A. tripolium plants from five different sites close to the seashore on the North Sea island Baltrum, from five different potash mine dumps and, as an outgroup, from the seashore in Japan were probed. DNA was extracted from five plants from each of the 11 A. tripolium populations and analyzed for random amplified polymorphic DNA (RAPD). Altogether 35 polymorphic bands in 51 individuals and 45 different detectable genotypes could be identified. For evaluation of the genetic variation using RAPD bands, the neighbor-joining method, the principal coordinate analysis, and the analysis of molecular variance were applied, resulting in the classification into three genetic groups. A. tripolium plants from different ecological habitats on Baltrum were closely related while the plants growing at the deposit dumps showed a higher genetic diversity. The Japanese population was genetically very different from the German populations. Correlations between phytosociological and soil parameters and the respective genotype were not significant. The results argue for a conservation of anthropogenically salt-contaminated habitats to maintain genetic variability not only on the species level, but also within a species.

Aster tripolium L. (Dollart, Germany) and Sesuvium portulacastrum L. (Dakhla, Morocco) are potential halophytic vegetables, fodder plants, and ornamentals for re-vegetating saline land. To compare their strategies involved in salt tolerance both plants were grown with 0%, 1.5%, and 3% ( Aster ) or 0%, 2.5%, and 5% ( Sesuvium ) NaCl in the watering solution. The growth rate was reduced in both species with increasing NaCl concentrations. The quotient of Na + /K + indicates that Aster accumulates more K + in comparison to Na + while the reverse is true for Sesuvium . Osmolality of the leaf sap increased with increasing NaCl concentration in both Aster and Sesuvium . Transpiration rate was severely reduced in both Aster (3%) and Sesuvium (5%) plants after 10 d of NaCl watering. The CO 2 assimilation rate decreased in Aster (3%) and Sesuvium (5%) NaCl-treated plants from day 5 to day 10. The most important results from chlorophyll fluorescence measurements were derived from the non-photochemical quenching analysis (NPQ). First, both plants had linearly increasing levels of NPQ with increasing NaCl concentrations. Second, Sesuvium had almost half the NPQ value when compared to Aster under increased soil salinity. In Aster P-ATPase activities were decreased in plants treated with 3% NaCl after three days of treatment, F-ATPase activities increased with increasing NaCl concentrations and no clear changes were measured in V-ATPase activities. In Sesuvium any changes could be observed in the three ATPase activities determined. To conclude, Aster and Sesuvium use different strategies in adaptation to soil salinity.

The treatment of Arabidopsis thaliana with methyl jasmonate was used to investigate the reaction of 2467 selected genes of primary and secondary metabolism by macroarray hybridization. Hierarchical cluster analysis allowed distinctions to be made between diurnally and methyl jasmonate regulated genes in a time course from 30 min to 24 h. 97 and 64 genes were identified that were up- or down-regulated more than 2-fold by methyl jasmonate, respectively. These genes belong to 18 functional categories of which sulfur-related genes were by far strongest affected. Gene expression and metabolite patterns of sulfur metabolism were analysed in detail, since numerous defense compounds contain oxidized or reduced sulfur. Genes encoding key reactions of sulfate reduction as well as of cysteine, methionine and glutathione synthesis were rapidly up-regulated, but none of the known sulfur-deficiency induced sulfate transporter genes. In addition, increased expression of genes of sulfur-rich defense proteins and of enzymes involved in glucosinolate metabolism was observed. In contrast, profiling of primary and secondary sulfur metabolites revealed only an increase in the indole glucosinolate glucobrassicin upon methyl jasmonate treatment. The observed rapid mRNA changes were thus regulated by a signal independent of the known sulfur deficiency response. These results document for the first time how comprehensively the regulation of sulfur-related genes and plant defense are connected. This interaction is discussed as a new approach to differentiate between supply- and demand-driven regulation of the sulfate assimilation pathway.

In several organisms d-cysteine desulfhydrase (d-CDes) activity (EC 4.1.99.4) was measured; this enzyme decomposes d-cysteine into pyruvate, H2S, and NH3. A gene encoding a putative d-CDes protein was identified in Arabidopsis thaliana (L) Heynh. based on high homology to an Escherichia coli protein called YedO that has d-CDes activity. The deduced Arabidopsis protein consists of 401 amino acids and has a molecular mass of 43.9 kDa. It contains a pyridoxal-5′-phosphate binding site. The purified recombinant mature protein had a Km for d-cysteine of 0.25 mm. Only d-cysteine but not l-cysteine was converted by d-CDes to pyruvate, H2S, and NH3. The activity was inhibited by aminooxy acetic acid and hydroxylamine, inhibitors specific for pyridoxal-5′-phosphate dependent proteins, at low micromolar concentrations. The protein did not exhibit 1-aminocyclopropane-1-carboxylate deaminase activity (EC 3.5.99.7) as homologous bacterial proteins. Western blot analysis of isolated organelles and localization studies using fusion constructs with the green fluorescent protein indicated an intracellular localization of the nuclear encoded d-CDes protein in the mitochondria. d-CDes RNA levels increased with proceeding development of Arabidopsis but decreased in senescent plants; d-CDes protein levels remained almost unchanged in the same plants whereas specific d-CDes activity was highest in senescent plants. In plants grown in a 12-h light/12-h dark rhythm d-CDes RNA levels were highest in the dark, whereas protein levels and enzyme activity were lower in the dark period than in the light indicating post-translational regulation. Plants grown under low sulfate concentration showed an accumulation of d-CDes RNA and increased protein levels, the d-CDes activity was almost unchanged. Putative in vivo functions of the Arabidopsisd-CDes protein are discussed.

Different field surveys have shown that sulphur (S) fertilization can increase the resistance of agricultural crops against fungal pathogens. The mechanisms of this sulphur-induced resistance (SIR) are, however, not yet known. Volatile S compounds are thought to play an important role because H(2)S is toxic to fungi. A field experiment was conducted to analyse the influence of S fertilization and the activity of H(2)S-releasing enzymes on fungal infections. Two levels of N and S fertilizers and two varieties of oilseed rape were investigated with respect to their potential to release H(2)S by the enzymatic activity of L-cysteine desulphydrase (LCD) and O-acetyl-L-serine(thiol)lyase (OAS-TL). LCD releases H(2)S during cysteine degradation, while OAS-TL consumes H(2)S during cysteine synthesis and free H(2)S is only released in a side reaction. All plots of the field trial showed an infection with Pyrenopeziza brassicae and leaf disc samples were taken from visibly infected leaf areas and apparently uninfected areas to investigate the reaction to the infection in relation to the treatments. Different S fractions and the activities of LCD and OAS-TL were measured to evaluate the potential to release H(2)S in relation to S nutrition and fungal infection. S fertilization significantly increased the contents of total S, sulphate, organic S, cysteine, and glutathione in the plants, but decreased LCD activity. Infection with P. brassicae increased cysteine and glutathione contents, as well as the activity of LCD. Therefore crops were able to react to a fungal infection with a greater potential to release H(2)S, which is reflected by an increasing LCD activity with fungal infection.

All members of the sulphotransferase (SOT, EC 2.8.2.-) protein family use 3'-phosphoadenosine 5'-phosphosulphate (PAPS) as the sulphuryl donor and transfer the sulphonate group to an appropriate hydroxyl group of several classes of substrates. These enzymes have highly conserved domains and can be found in eubacteria and eukaryotes. In mammals, sulphate conjugation catalysed by SOTs constitutes an important reaction in the transformation of xenobiotics, and in the modulation of the biological activity of steroid hormones and neurotransmitters. In plants, sulphate-conjugation reactions seem to play an important role in plant growth, development, and adaptation to stress. To date only a few plant SOTs have been characterized in detail. The flavonol 3- and 4'-SOTs from Flaveria species (Asteraceae), which catalyse the sulphonation of flavonol aglycones and flavonol 3-sulphates, respectively, were the first plant SOTs for which cDNA clones were isolated. The plasma membrane associated gallic acid SOT of Mimosa pudica L. pulvini cells may be intrinsic to signalling events that modify the seismonastic response. In Brassica napus L. a SOT catalyses the O-sulphonation of brassinosteroids and thereby abolishes specifically the biological activity of 24-epibrassinolide. The fully sequenced genome of Arabidopsis thaliana Heynh. contains in total 18 genes that are likely to encode SOT proteins based on sequence similarities of the translated products with an average identity of 51.1%. So far only one SOT from A. thaliana (At5g07000) was functionally characterized: the protein was shown to catalyse the sulphonation of 12-hydroxyjasmonate and thereby inactivate excess jasmonic acid in plants. The substrates and, therefore, the physiological roles of SOTs are very diverse. By using the numerous informative databases and methods available for the model plant A. thaliana, the elucidation of the functional role of the SOT protein family will be accelerated.

Sulfurtransferases (Str) comprise a group of enzymes widely distributed in archaea, eubacteria, and eukaryota which catalyze the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors. In all organisms analyzed to date, small gene families encoding Str proteins have been identified. The gene products were localized to different compartments of the cells. Our interest concerns the localization of Str proteins encoded in the nuclear genome of Arabidopsis. Computer-based prediction methods revealed localization in different compartments of the cell for six putative AtStrs. Several methods were used to determine the localization of the AtStr proteins experimentally. For AtStr1, a mitochondrial localization was demonstrated by immunodetection in the proteome of isolated mitochondria resolved by one- and two-dimensional gel electrophoresis and subsequent blotting. The respective mature AtStr1 protein was identified by mass spectrometry sequencing. The same result was obtained by transient expression of fusion constructs with the green fluorescent protein in Arabidopsis protoplasts, whereas AtStr2 was exclusively localized to the cytoplasm by this method. Three members of the single-domain AtStr were localized in the chloroplasts as demonstrated by transient expression of green fluorescent protein fusions in protoplasts and stomata, whereas the single-domain AtStr18 was shown to be cytoplasmic. The remarkable subcellular distribution of AtStr15 was additionally analyzed by transmission electron immunomicroscopy using a monospecific antibody against green fluorescent protein, indicating an attachment to the thylakoid membrane. The knowledge of the intracellular localization of the members of this multiprotein family will help elucidate their specific functions in the organism.

The effects of the chloroacetanilide herbicide metazachlor have been investigated in outdoor artificial mesocosms. Decreasing phytoplankton densities were caused by the application, however, the communities recovered after 30 to 35 days. Periphyton growth was found to be affected not only by the herbicide application but by the presence of species with different ability to grow on artificial substrates. Zooplankton diversity was small due to low density of ingestible algae species. Oxygen saturation was found to be correlated with the dosage levels of the herbicide in the second half of the study. Effekte des Herbizids Metazachlor auf Phytoplankton- und Periphyton-Gemeinschaften in Freiland-Mesokosmen Es wurden die Effekte des Chloracetanilid-Herbizids Metazachlor auf Freiland-Mesokosmen untersucht. Infolge der Herbizidapplikation lagen geringe und konzentrationsabhangige Phytoplanktondichten vor, nach 30 bis 35 Tagen traten Erholungseffekte auf. Das Wachstum von Periphyton wurde nicht nur durch die Herbizidapplikation beeinflusst, sondern auch durch die unterschiedliche Fahigkeit zum Wachstum auf kunstlichen Substraten. Eine insgesamt geringe Phytoplanktondichte induzierte eine schwache Abundanz des Zooplanktons. Die Sauerstoffsattigung in der zweiten Halfte der Studie korrelierte mit der Dosierung des Herbizids.

Sulfurtransferases (STs) and beta-cyano- l-alanine synthase (CAS) are suggested to be involved in cyanide detoxification. Therefore, the accumulation of ST1 and CAS RNAs, and the ST and CAS protein levels and enzyme activities were determined in Arabidopsis thaliana Heynh. plants grown under different conditions. Senescence-associated processes were successfully induced by natural aging, by jasmonate methyl ester and by darkness in whole plants and detached leaves, as demonstrated by the expression of the senescence marker genes SAG12 and SAG13. However, the changes in RNA accumulation and protein levels of ST and CAS did not correlate with the expression of these senescence marker genes; the specific ST and CAS activities either decreased (ST) or increased (CAS). In another experiment, Arabidopsis plants were sprayed with cyanide to investigate the role of ST and CAS in cyanide detoxification. The expression of ST and CAS at the RNA and protein levels, and also the enzyme activities, remained equal in cyanide-treated and control plants. Incubation with 1-aminocyclopropane-1-carboxylic acid, the precursor of ethylene, increased while fumigation with ethylene decreased expression and activity of ST and CAS. In summary, cyanide does not induce the expression or enhance the activity of ST and CAS in Arabidopsis. For both proteins the evidence for a role in cyanide detoxification or induced senescence is low.

Sulfotransferases (SOTs) (EC 2.8.2.-) play a crucial role in the glucosinolate (Gl) biosynthesis, by catalyzing the final step of the core glucosinolate formation. In Arabidopsis thaliana the three desulfo (ds)-Gl SOTs AtSOT16, AtSOT17 and AtSOT18 were previously characterized, showing different affinities to ds-Gls. But can the knowledge about these SOTs be generally transferred to other Gl-synthesizing plants? It was investigated how many SOTs are present in the economically relevant crop plant Brassica napus L., and if it is possible to predict their characteristics by sequence analysis. The recently sequenced B. napus is a hybrid of Brassica rapa and Brassica oleracea . By database research, 71 putative functional BnSOT family members were identified and at least eleven of those are putative ds-Gl SOTs. Besides the homologs of AtSOT16 – 18, phylogenetic analyses revealed new subfamilies of ds-Gl SOTs, which are not present in A. thaliana . Three of the B. napus ds-Gl SOT proteins were expressed and purified, and characterized by determining the substrate affinities to different ds-Gls. Two of them, BnSOT16-a and BnSOT16-b, showed a significantly higher affinity to an indolic ds-Gl, similarly to AtSOT16. Additionally, BnSOT17-a was characterized and showed a higher affinity to long chained aliphatic Gls, similarly to AtSOT17. Identification of homologs to AtSOT18 was less reliable, because putative SOT18 sequences are more heterogeneous and confirmation of similar characteristics was not possible.

Water deficit is strongly affecting plant development and production. With the decrease in rainfall in many areas and the shortage of arable land for growing food crops, there is a demand to find alternative plant species that could be cultivated in non-arable land for food supplies and bioenergy. Balanites aegyptiaca L. is a multi-purpose tree belonging to the family of Balanitaceae distributed in North and West Africa, and West Asia. The species is considered as drought-tolerant serving as a source of many secondary metabolites and having a potential for biofuel production. This study aimed to examine and compare the morpho-physiological responses to water stress of six different B. aegyptiaca genotypes collected from different regions. Different regimes of soil volumetric water content (VWC 35% as a control, VWC 20% as moderate and VWC 5% as a severe drought stress) were chosen to finally select the most drought-tolerant genotype under greenhouse conditions. Several growth parameters, stomata conductance, photosynthetic efficiency, infrared thermography and metabolites contents were analyzed to investigate and compare the drought impact among B. aegyptiaca genotypes. The results indicate that at severe drought stress each genotype has an independent strategy to cope with the water shortage through a significant reduction in biomass parameters, early stomata closure combined with small changes in photosynthetic activity and producing a high concentration of ascorbic acid and proline. Finally, we found that i) Balanites genotypes showed different morphological and physiological responses to cope with the water shortage, ii) collections of two or three parameters could distinguish the water stress levels among the genotypes, and iii) genotype El-Kharga showed the highest drought-tolerance compared to the other genotypes. It shows the lowest magnitude of biomass reduction and early stomata closure as strategy of saving leaf water content under severe drought stress.

Sulfurtransferases/rhodaneses (ST) are a group of enzymes widely distributed in all three phyla that catalyze the transfer of sulfur from a donor to a thiophilic acceptor substrate. All ST contain distinct structural domains, and can exist as single-domain proteins, as tandemly repeated modules in which the C-terminal domain bears the active site, or as members of multi-domain proteins. We identified several ST in Arabidopsis resembling the C-terminus of the Arabidopsis two-domain ST1 and the single-domain GlpE protein from Escherichia coli. Two of them (accession numbers BAB10422 and BAB10409) were expressed in E. coli and purified. Both proteins showed thiosulfate-specific ST enzyme activity.

Summary Protoporphyrin IX is the last common intermediate of tetrapyrrole biosynthesis. The chelation of a Mg2+ ion by magnesium chelatase and of a ferrous ion by ferrochelatase directs protoporphyrin IX towards the formation of chlorophyll and heme, respectively. A full length cDNA clone encoding a ferrochelatase was identified from a Nicotiana tabacum cDNA library. The encoded protein consists of 497 amino acid residues with a molecular weight of 55.4 kDa. In vitro import of the protein into chloroplasts and its location in stroma and thylakoids confirm its close relationship to the previously described Arabidopsis thaliana plastid-located ferrochelatase (FeChII). A 1700-bp tobacco FeCh cDNA sequence was expressed in Nicotiana tabacum cv. Samsun NN under the control of the CaMV 35S promoter in antisense orientation allowing investigation into the consequences of selective reduction of the plastidic ferrochelatase activity for protoporphyrin IX channeling in chloroplasts and for interactions between plastidic and mitochondrial heme synthesis. Leaves of several transformants showed a reduced chlorophyll content and, during development, a light intensity-dependent formation of necrotic leaf lesions. In comparison with wild-type plants the total ferrochelatase activity was decreased in transgenic lines leading to an accumulation of photosensitizing protoporphyrin IX. Ferrochelatase activity was reduced only in plastids but not in mitochondria of transgenic plants. By means of the specifically diminished ferrochelatase activity consequences of the selective inhibition of protoheme formation for the intracellular supply of heme can be investigated in the future.

The last step in cysteine biosynthesis is catalysed by the pyridoxal 5’-phosphate-dependent enzyme O -acetyl-L-serine(thiol)lyase (OAS-TL). Several isoforms are localized in different compartments of the cell. OAS-TL and OAS-TL-like proteins also catalyse the formation of β-cyanoalanine and sulfide; the release of sulfide and of an unknown product was also observed. In Arabidopsis plants of different age, the OAS-TL activity decreased with increasing age whereas the enzymatical sulfide release from cysteine increased in older plants. The β-cyanoalanine synthase showed two activity peaks during the time course investigated. During a 12-h light/12-h dark rhythm, the OAS-TL and the sulfide-releasing activities ran parallel with a maximum in the light phase and a decrease of enzyme activity in the dark phase. β-Cyanoalanine synthase activities did not follow a special pattern. Three genes coding for the OAS-TL isoforms A, B, and C, which are presumably localized in the cytoplasm, in plastids, and in mitochondria, respectively, were differentially expressed. The mRNA steady-state levels of the three proteins varied at different developmental stages. The results are discussed with respect to the physiological relevance in the plant organism.

A mutation in the Arabidopsis gene STARIK leads to dwarfism and chlorosis of plants with an altered morphology of leaf and cell nuclei. We show that the STARIK gene encodes the mitochondrial ABC transporter Sta1 that belongs to a subfamily of Arabidopsis half-ABC transporters. The severity of the starik phenotype is suppressed by the ectopic expression of the STA2 homolog; thus, Sta1 function is partially redundant. Sta1 supports the maturation of cytosolic Fe/S protein in Deltaatm1 yeast, substituting for the ABC transporter Atm1p. Similar to Atm1p-deficient yeast, mitochondria of the starik mutant accumulated more nonheme, nonprotein iron than did wild-type organelles. We further show that plant mitochondria contain a putative l-cysteine desulfurase. Taken together, our results suggest that plant mitochondria possess an evolutionarily conserved Fe/S cluster biosynthesis pathway, which is linked to the intracellular iron homeostasis by the function of Atm1p-like ABC transporters.

Sulfurtransferases transfer a sulfane atom from a donor substrate to a thiophilic acceptor molecule. Recently a sulfurtransferase specific for the substrate 3-mercaptopyruvate was isolated from Arabidopsis thaliana [Papenbrock, J. & Schmidt, A. (2000) Eur. J. Biochem. 267, 145-154]. In this study a second sulfurtransferase from Arabidopsis was characterized and compared to the enzyme described previously. Sequences of the mature proteins had an identity of 77.7%. The plant sulfurtransferases formed a distinct group within the known eukaryotic sulfurtransferases. When Southern blots were hybridized with labelled cDNA fragments from each of the plant sulfurtransferases the same pattern of bands was obtained indicating the existence of only these two closely related sulfurtransferases. The new sulfurtransferase was expressed in Escherichia coli fused with an N-terminal His6-tag, purified and tested for enzyme activity. Like the first enzyme, the newly isolated protein preferred 3-mercaptopyruvate to thiosulfate as substrate. The Km of both enzymes determined for 3-mercaptopyruvate and cyanide were almost identical. As a result of database searches it became obvious that sulfurtransferase proteins from higher plants showed high similarities to small senescence- and stress-induced proteins. To prove the involvement of sulfurtransferases in senescence-associated processes 3-mercaptopyruvate sulfurtransferase activity was determined in crude protein extracts from Arabidopsis plants of different ages. 3-mercaptopyruvate sulfurtransferase activity and steady-state RNA levels of sulfurtransferases increased with increasing age. However, steady-state protein levels as measured by using an antibody against the sulfurtransferase protein expressed previously decreased. Putative roles of sulfurtransferases in senescence-associated processes are discussed.

Magnesium-protoporphyrin IX chelatase (Mg-chelatase) is located at the branchpoint of tetrapyrrole biosynthesis, at which point protoporphyrin IX is distributed for the synthesis of chlorophyll and heme. We investigated the regulatory contribution of Mg-chelatase to the flow of metabolites. In plants, the enzyme complex consists of three subunits, designated CHL D, CHL I, and CHL H. Transgenic tobacco (Nicotiana tabacum) plants expressing antisense RNA for the Mg-chelatase subunit CHL H were analyzed to elucidate further the role of Mg-chelatase in the distribution of protoporphyrin IX into the branched tetrapyrrolic pathway. The transgenic plants displayed a reduced growth rate and chlorophyll deficiency. Both phenotypical properties were correlated with lower Mg-chelatase activity. Unexpectedly, less protoporphyrin IX and heme accumulated, and a decrease in 5-aminolevulinate (ALA)-synthesizing capacity and ALA dehydratase activity paralleled the progressive reduction in Mg-chelatase activity in the transformants compared with control plants. The reduced activities of the early enzymatic steps corresponded with lower levels of transcripts encoding glutamyl-tRNA reductase and ALA-dehydratase. The decreased expression and activities of early enzymes in the pathway could be explained by a feedback-controlled mechanism in response to lower Mg-chelatase activity. We discuss intercompartmental signaling that synchronizes the activities of the first steps in tetrapyrrolic metabolism with the late steps for the synthesis of end products.