Sulfur Supply Research Articles

Sulfur regulates iron uptake and iron use efficiency in bread and durum wheat

Present study elucidates the role and physiological basis of sulfur (S) mediated iron (Fe) regulation, uptake and use efficiency under deficient availability of soil Fe (4–6 ppm) at different level of applied S [0 (S0), 30 (S30) and 60 (S60) kg ha−1] in bread and durum wheat. Sulfur supply at S30 and S60 greatly improved the Fe and S uptake of the wheat cultivars over S0. Bread wheat recorded a greater agronomic SUE than the durum wheat but it declined with S application in a dose dependent manner in both the wheat cultivars. Further, the increase in grain yield and grain Fe under S application than without it in both the cultivars may also be related to phytosiderophore mediated higher root Fe uptake, and root to shoot and to grain translocation of Fe and subsequent induction of Fe deficiency tolerance response, more so in bread wheat than the durum wheat. It is suggested that the effect of S on Fe uptake under Fe deficient condition may be mediated via an increase in S supply regulated biosynthesis of phytosiderophore and their consequent release in rhizosphere. Results indicate two way interaction between Fe and S, at the rhizosphere and at the plant level.

The effect of excess sulfate supply on iron accumulation in three graminaceous plants at the early vegetative phase

In recent years it has been established a significant relationship between sulfur (S) and iron (Fe) nutrition. In particular, it has been demonstrated that S deprivation can hinder Fe acquisition in barley, maize and wheat. This can be explained by assuming that, in order to cope with low Fe availability in the soil, grasses have evolved a phytosiderophores (PS)-based Fe chelation system (Strategy II) and PS are synthesized from methionine, through a nicotianamine intermediate.On the other hand, it has been demonstrated that wheat plants exhibit a higher Fe accumulation when supplied with excess S concentration, this effect being especially beneficial under severely limited Fe supply.The goal of this study was to explore whether the higher ability to acquire Fe, induced by a higher S supply, might be a general response of graminaceous species.The response of durum wheat (Triticum durum L.), barley (Hordeum vulgare L.), and maize (Zea mays L.) to the excess of S availability (2.4mM vs 1.2mM which is considered as optimal) was studied as a function of Fe availability (limited and sufficient, 20 and 80μM, respectively). At the end of the experimental period, which lasted 11 days, growth parameters (shoot and root fresh weight and chlorophyll content), total S and Fe concentrations, and PS release rate were compared among the three species. Furthermore, we evaluated plant sulfate uptake capability, by analysing the expression of genes coding for high affinity sulfate transporter (TdST1.1, HvST1.1 and ZmST1.1) in roots of each graminaceous plant.Our preliminary findings are largely consistent with the apparent divergence among the three species. In particular, an excess S supply may result in the improvement of Fe use efficiency in durum wheat plants, but not in both barley and maize.The use of higher S supply seems to be a promising approach, at least for wheat plants, which can both reduce agricultural demand for Fe fertilizers and improve the Fe use efficiency of plants.

Interaction between sulfur and lead in toxicity, iron plaque formation and lead accumulation in rice plant

Human activities have resulted in lead and sulfur accumulation in paddy soils in parts of southern China. A combined soil–sand pot experiment was conducted to investigate the influence of S supply on iron plaque formation and Pb accumulation in rice (Oryza sativa L.) under two Pb levels (0 and 600mgkg−1), combined with four S concentrations (0, 30, 60, and 120mgkg−1). Results showed that S supply significantly decreased Pb accumulation in straw and grains of rice. This result may be attributed to the enhancement of Fe plaque formation, decrease of Pb availability in soil, and increase of reduced glutathione (GSH) in rice leaves. Moderate S supply (30mgkg−1) significantly increased Fe plaque formation on the root surface and in the rhizosphere, whereas excessive S supply (60 and 120mgkg−1) significantly decreased the amounts of iron plaque on the root surface. Sulfur supply significantly enhanced the GSH contents in leaves of rice plants under Pb treatment. With excessive S application, the rice root acted as a more effective barrier to Pb accumulation compared with iron plaque. Excessive S supply may result in a higher monosulfide toxicity and decreased iron plaque formation on the root surface during flooded conditions. However, excessive S supply could effectively decrease Pb availability in soils and reduce Pb accumulation in rice plants.

Enhanced arsenic sensitivity with excess phytochelatin accumulation in shoots of a SULTR1;2 knockout mutant of Arabidopsis thaliana (L.) Heynh

ABSTRACTOne mechanism of arsenic detoxification in plants is synthesis of phytochelatins from glutathione in a sulfur-dependent manner. This study examined the contribution of a sulfate transporter, SULTR1;2, in arsenic tolerance in terms of sulfur metabolism in Arabidopsis thaliana (L.) Heynh. Comparative analysis of SULTR mutants showed that defective mutations of SULTR1;2 resulted in an increased arsenic sensitivity, in both shoots and roots, establishing that SULTR1;2 is required for arsenic tolerance. We subsequently quantified total sulfur content and levels of sulfur compounds (phytochelatins, glutathione, cysteine) in a SULTR1;2 mutant, sel1-8. Arsenic treatments increased sulfur uptake of sel1-8, but the mutant was unable to maintain the proper basal level of sulfur. Despite drastic reduction of total sulfur content, the mutant accumulated substantial or rather excess phytochelatins in shoots under arsenic stress conditions. The levels of glutathione and cysteine in shoots were lower in sel1-8 than in the wild type, possibly representing partial disorder of sulfur nutrition under limited sulfur supply. Taken together, we propose that SULTR1;2 contributes to arsenic tolerance by maintaining proper sulfur nutrient status at high demand for sulfur by phytochelatins-synthetic pathway, and/or optimal level of phytochelatin synthesis in shoots.

Effect of divided nitrogen and sulfur fertilization on the quality of winter wheat

The ecological characteristics and agro-ecological conditions in Hungary provide opportunities for quality wheat production. For the successful wheat production besides the favorable conditions; the proper use of expertise and appropriate cultivation techniques are not negligible. Successful cultivation affected by many factors. To some extent we can affect, influence and convert the abiotic factors.
 Today, a particularly topical issue is the question of nutrition and that the species’ genetic code can be validated using the appropriate quantity and quality fertilizer. Beyond determining the fertilizer requirements of the winter wheat it is important to align the nutrient to the plant’s nutrient uptake dynamics and to ensure its shared dispensing. In any case, it is important to note the use of autumnal base-fertilizer as complex fertilizer. Hereafter sharing the fertilizer during the growing season with the recommended adequate nitrogen dose.The first top dressing of winter wheat in early spring (the time of tillering) can be made, the second top dressing at the time of stem elongation, and the third top dressing at the end of the blooming can be justified. Determining the rate of fertilizer application depends on the habitat conditions and the specific nutrient needs of plants. In autumn the 1/3 of the planned amount of basic fertilizer should be dispensed (in case of N). During setting our experiment we used 3 doses (0 kg ha-1 N-1 active ingredient; 90 kg ha-1 N-1 active ingredients and 150 kg ha-1 N-1 active ingredient). Application dates beyond the autumn basic fertilization are the following: in one pass in early spring, divided in early spring and the time of run up, early spring and late flowering. In addition to nitrogen the replacement of sulfur gets a prominent role as a result of decreased atmospheric inputs. The proper sulfur supply mainly affects the quality parameters. It influences positively the wheat flour’s measure of value characteristics (gluten properties, volume of bread, dough rheology.
 In terms of nitrogen doses; the larger amounts (150 kg ha-1 N-1 drug), is the proposed distributed application, while in the case of lower nitrogen (90 kg ha-1 N-1 drug) in a single pass in the early spring can achieve better results. After using sulfur the quality values among the nutritional parameters that can be associated with gluten properties took up higher values than the samples not treated with sulfur.

Food safety: Structure and expression of the asparagine synthetase gene family of wheat

Asparagine is an important nitrogen storage and transport molecule, but its accumulation as a free amino acid in crops has implications for food safety because free asparagine is a precursor for acrylamide formation during cooking and processing. Asparagine synthesis occurs by the amidation of aspartate, catalysed by asparagine synthetase, and this study concerned the expression of asparagine synthetase (TaASN) genes in wheat. The expression of three genes, TaASN1-3, was studied in different tissues and in response to nitrogen and sulphur supply. The expression of TaASN2 in the embryo and endosperm during mid to late grain development was the highest of any of the genes in any tissue. Both TaASN1 and TaASN2 increased in expression through grain development, and in the grain of field-grown plants during mid-development in response to sulphur deprivation. However, only TaASN1 was affected by nitrogen or sulphur supply in pot-based experiments, showing complex tissue-specific and developmentally-changing responses. A putative N-motif or GCN4-like regulatory motif was found in the promoter of TaASN1 genes from several cereal species. As the study was completed, a fourth gene, TaASN4, was identified from recently available genome data. Phylogenetic analysis showed that other cereal species have similar asparagine synthetase gene families to wheat.

Editorial: Frontiers of Sulfur Metabolism in Plant Growth, Development, and Stress Response.

Plants assimilate inorganic sulfur and metabolize it further to organic sulfur compounds essential for plant growth, development, and stress mitigation. Animals including humans in turn depend on plants and microorganisms providing these essential compounds, such as the amino acid methionine, which they cannot synthesize. Furthermore, a number of sulfur-containing metabolites provide the characteristic tastes and smells of our food, and many of them are known to have health promoting and protective properties. Thus, adequate supply of sulfur can be a critical factor affecting crop yield and production of beneficial phytochemicals. However, because of the reduction in anthropogenic emission of sulfur dioxide to the atmosphere, particularly from developed countries, sulfur deficiency has become a problem for agriculture and in many areas sulfur fertilization is required to ensure yield, quality, and health of crops. Such an impact of sulfur has triggered research into mechanisms of sulfur metabolism in plants and its regulation. Indeed great progress has been made over the last decades as summarized in several recent reviews (Takahashi et al., 2011; Sauter et al., 2013; Calderwood and Kopriva, 2014). Starting with identification of genes encoding components of sulfur metabolism, research in molecular biology and molecular genetics has brought us toward finding regulators and signals controlling the pathway (Maruyama-Nakashita et al., 2006; Gigolashvili et al., 2007; Hirai et al., 2007), and describing natural variation in diverse sulfur related traits (Kliebenstein et al., 2001; Loudet et al., 2007; Chao et al., 2014). In addition, questions related to regulation of sulfur metabolism have been on the forefront of systems biology (Maruyama-Nakashita et al., 2003; Hirai et al., 2005; Nikiforova et al., 2005) and quantitative genetics (Loudet et al., 2007). This research topic organized in Frontiers in Plant Science has been an opportunity to present our current understanding and research progress focused on a number of interesting aspects in plant sulfur metabolism. We aimed to cover broad research topics in sulfur nutrition and metabolism by compiling diverse types of articles: original research reports to exemplify new information on questions the sulfur research community is addressing, focused reviews to provide detailed updates to specific topics, and perspectives to review a progress but also to address the questions for the next decade(s) of research. This concept found indeed a great support in the sulfur research community with 34 articles contributed by scholars representing wide disciplinary areas.

Compartmentalization and Regulation of Sulfate Assimilation Pathways in Plants.

Plants utilize sulfate to synthesize primary and secondary sulfur-containing metabolites required for growth and survival in the environment. Sulfate is taken up into roots from the soil and distributed to various organs through the functions of membrane-bound sulfate transporters, while it is utilized as the primary substrate for synthesizing sulfur-containing metabolites in the sulfate assimilation pathways. Transporters and enzymes for the assimilative conversion of sulfate are regulated in highly organized manners depending on changes in sulfate supply from the environment and demand for biosynthesis of reduced sulfur compounds in the plant systems. Over the past few decades, the effect of sulfur nutrition on gene expression of sulfate transporters and assimilatory enzymes has been extensively studied with the aim of understanding the full landscape of regulatory networks.

Impact Assessment of Oilseed F Based Front Line Demonstration on Rapeseed and Mustard

The present study was carried out in Sehore district of Madhya Pradesh by Krishi Vigyan Kendra, Sehore. Total numbers of 81 front line demonstrations on mustard crop were conducted in different locations at farmers ’field to promote the cultivation and increase the adoption of improved package of practice. The seeds of improved varieties with seed treatment and use of rizhobium culture, and balanced fertilizers were the part of technological components supplied to the demonstration plot as against control. All the demonstrations were carried out in close coordination of scientist and farmers as well. Results revealed that improved varieties and balanced fertilization increased yield to the tune of 6.2% and 9.6%, respectively. While both the factors in combination were contributing 15.8% increase in yield. In demonstration plots C: B ratio was also obtained in demonstration fields was also higher as compared to control ones. It was suggested that while selecting the inputs for mustard balance fertilization (N: P: K 100: 80: 40) with additional supply of sulphur @ 30 Kg/ha should be given priority.

Does mineral sulphur availability account for growth performance, bulb development and metabolically related traits in wild leek (Allium ampeloprasum L.; Alliaceae)?

Allium ampeloprasum (L.) is a spontaneous biennial bulbous plant widespread across landscapes in the Mediterranean area, and has the potential to be used as a vegetable. Physiological and biochemical performance of this threatened vegetable was analyzed to investigate possible responses of sulphur (S) fertilization and how these relate to both ecological success and agronomic potential. Twenty-one-day-old plants were grown for 45 or 90 days at different sulphate concentrations in nutrient solution (0.01, 0.75, 1.5 and 4.5mM SO42–). When all aboveground organs had senesced, the pots were harvested for reproductive output, i.e., mother and daughter bulbs. Sulphur deficiency significantly reduced vegetative biomass, which was closely associated with sulphate supply. Sulphur supply resulted in larger daughter bulbs with trade-offs between offspring number and size. The S content in shoots provided evidence of reduced daughter bulb mass in the low S treatment. The metabolically related traits were dependent on S supply and plant organs, which evolve an inverse trend between shoots and roots. Wild leek is sensitive to S deficiency and plants are able to cope with fluctuating S availability from 0.01 to 4.5mM SO42–, whereas the initial S reserves in bulbs are likely to play an additional role in S-deficient soils. Overall, knowing the plant's optimal S nutritional status is of crucial importance in terms of crop management, which provides insight in how to produce wild leek, and potentially other Alliums, in the field with higher crop yield and enhanced product quality.

Glutathione homeostasis and Cd tolerance in the Arabidopsis sultr1;1-sultr1;2 double mutant with limiting sulfate supply.

Cadmium sensitivity in sultr1;1 - sultr1;2 double mutant with limiting sulfate supply is attributed to the decreased glutathione content that affected oxidative defense but not phytochelatins' synthesis. In plants, glutathione (GSH) homeostasis plays pivotal role in cadmium (Cd) detoxification. GSH is synthesized by sulfur (S) assimilation pathway. Many studies have tried to investigate the role of GSH homeostasis on Cd tolerance using mutants; however, most of them have focused on the last few steps of S assimilation. Until now, mutant evidence that explored the relationship between GSH homeostasis on Cd tolerance and S absorption is rare. To further reveal the role of GSH homeostasis on Cd stress, the wild-type and a sultr1;1-sultr1;2 double mutant which had a defect in two distinct high-affinity sulfate transporters were used in this study. Growth parameters, biochemical or zymological indexes and S assimilation-related genes' expression were compared between the mutant and wild-type Arabidopsis plants. It was found that the mutations of SULTR1;1 and SULTR1;2 did not affect Cd accumulation. Compared to the wild-type, the double mutant was more sensitive to Cd under limited sulfate supply and suffered from stronger oxidative damage. More importantly, under the same condition, lower capacity of S assimilation resulted in decreased GSH content in mutant. Faced to the limited GSH accumulation, mutant seedlings consumed a large majority of GSH in pool for the synthesis of phytochelatins rather than participating in the antioxidative defense. Therefore, homeostasis of GSH, imbalance between antioxidative defense and severe oxidative damage led to hypersensitivity of double mutant to Cd under limited sulfate supply.

Arsenic toxicity in rice (Oryza sativa L.) is influenced by sulfur supply: Impact on the expression of transporters and thiol metabolism

Arsenic (As) is a non-essential element whose entry into rice grains is an issue of public concern. The need, therefore, exists to understand the regulatory mechanisms of As accumulation and distribution patterns in plants. This study analyzed the effect of sulfur (S) supply on As accumulation and distribution in rice (Oryza sativa L. var. IR64) plants. Nine day old seedlings were grown in 0.798mM S (Normal S), 0.2mM S (Low S) and 0.003mM S (Zero S) for 7days and then subjected to AsIII (20μM) exposure for 7–15days. The concentration of As varied significantly in different S treatments with a consistent trend of decrease in As concentration in depleted S supply treatments on both 7days and 15days. Arsenic concentration declined from 726μgg−1 DW to 537μgg−1 DW in roots and from 29μgg−1 DW to 8μgg−1 DW in shoots at 7days, and from 1536μgg−1 DW to 1062 in roots and from 58μgg−1 DW to 16μgg−1 DW in shoots at 15days, when S supply declined from normal to zero. The subcellular distribution of As was also found to vary with alteration in S supply and also differentially in shoot and root. In general, an up-regulation of sulfate transporters of groups 1 and 2 was observed while As transporters (Lsi1 and Lsi2) were down-regulated in response to As exposure to maintain sulfate and to regulate As levels. In spite of S depletion, an increase in cysteine, glutathione (GSH) and phytochelatin (PC) levels was observed upon As exposure. However, some negative impact of S depletion and As could be seen on the growth of plants. The study concluded that even in conditions of decreased S availability, plants continue to rely on thiol metabolism to tackle As levels and its toxicity effectively and altered subcellular distribution of As contributes only partially.

Pyritic event beds and sulfidized Fe (oxyhydr)oxide aggregates in metalliferous black mudstones of the Paleoproterozoic Talvivaara formation, Finland

The Paleoproterozoic, 2.0–1.9 Ga Talvivaara formation of Finland was deposited during the Shunga Event, a worldwide episode of enhanced accumulation of organic-rich sediments in the aftermath of the Lomagundi–Jatuli carbon isotope excursion. Sulfidic carbonaceous mudstones in the Talvivaara formation contain one of the largest known shale-hosted nickel deposits. In order to gain new insight into this Shungian sedimentary environment, sedimentological, petrographical and in situ S and Fe isotopic microanalyses were carried out on samples representing depositional and early-diagenetic conditions. The event-bedded lithology with tidal signatures in the organic-rich mudstones strongly indicates deposition from predominantly river-delivered mud on a highly-productive coastal area, below storm-wave base. The riverine supply of phosphorus, sulfate and iron supported high primary productivity and resulted in strong lateral and vertical chemical gradients in the nearshore waters with a shallow oxic surface layer underlain by euxinic water. The stratigraphic upper part of the Talvivaara formation contains banded intervals of thin alternating pyrite beds and carbonaceous mudstone beds. The pyrite beds were deposited by seaward excursions of the concentrated, acidic Fe-rich river plume subsequent to droughts or dry seasons, which led to intense pyrite precipitation upon mixing with euxinic waters. δS34 and δFe56 values of the bedded pyrite (median δS34=−10.3‰ and δFe56=−0.79‰) are consistent with the reaction of dissolved Fe(II) with H2S from bacterial sulfate reduction. Organic-rich clayey Fe-monosulfide-bearing granules were transported from the muddy estuary, and enclosed in Fe (oxyhydr)oxide aggregates that were forming by wave and current reworking in nearshore accumulations of river-delivered iron. The isotopic composition of these presently pyrrhotitic inclusions (median δS34=−3.3‰ and δFe56=−1.6‰) indicates microbial iron reduction. The Fe (oxyhydr)oxide aggregates were transported in muddy debris flows to the distal euxinic seafloor. Their Fe (oxyhydr)oxide matrix was replaced by pyrite (median δS34=+5.8‰ and δFe56=+0.81‰) at shallow sediment depths with 34S and 56Fe-enriched porewater. Wavy-crinkly laminae of possible microbial origin developed on the euxinic seafloor during low sedimentation. These results indicate episodic deposition at seasonal to multiannual time scales. δS34 and δFe56 values in the studied Fe-sulfides provide evidence of microbial isotope fractionation processes and syndepositional and early-diagenetic origin, finding no support for the previously proposed local hydrothermal activity in the Talvivaara mudstones.

Sufficient sulfur supply promotes seedling growth, alleviates oxidation stress, and regulates iron uptake and translocation in rice

We investigated the effect of sulfur (S) supply on growth, oxidative stress, and iron uptake and transport in rice (Oryza sativa L.) seedlings using a hydroponic culture with four S concentrations (0, 1.75, 3.5, and 7.0 mM). The length and fresh mass of seedlings were enhanced with the increased S concentration. In addition, the content of thiobarbituric acid reactive substances (TBARS) in rice leaves was the highest when no S was added to the nutrition solution and gradually declined with the increasing S supply. The higher S nutrition reduced the amount of Fe plaque on rice roots and increased Fe content in roots and leaves. The content of nicotianamine was significantly higher in rice roots under the S deficiency, whereas the reverse trend was observed in rice shoots. Taken together, the sufficient S nutrition promoted growth of rice, reduced oxidative stress, and ensured normal Fe uptake and distribution.

Iron behavior in a northern estuary: Large pools of non-sulfidized Fe(II) associated with organic matter

The estuaries of the Northern Baltic Sea (Gulf of Bothnia) receive an abundance of diagenetically reactive catchment-derived Fe, which is to a large degree complexed with organic matter or present as Fe (hydr-)oxides. However, our understanding of sedimentary Fe diagenesis in these estuaries is limited. To address this limitation, the present study examines Fe geochemistry in a 3.5-m-thick estuarine benthic mud layer and three samples of suspended particulate matter of a catchment on the eastern Gulf of Bothnia. The age–depth model of the mud, constructed on the basis of sedimentary features as well as 137Cs and aquatic plant 14C determinations, revealed a high average rate of sedimentation (5cm·yr−1) for the upper mud unit (0–182.5cm, corresponding to 1973–2011), in response to intensive land-use (ditching) in the catchment since the 1960s and 1970s. The intensive land-use has resulted in a strong increase in the Fe accumulation rates, but has not caused a recognizable impact on the diagenetic processes of Fe including features such as degree of sulfidization and solid-phase partitioning. Iron X-ray absorption spectroscopy (XAS) indicated that in the suspended particulate matter, large proportions (47–58%) of Fe occur as Fe(III)-organic complexes and 2-line ferrihydrite. In the mud, the former is completely reduced, and reactive Fe (defined via extraction with 1M HCl) was high throughout (52–68%, median=61%) and strongly dominated by Fe(II). This reactive Fe(II) pool was sulfidized to only a limited extent (degree of reactive sulfidization=11–26%, median=17%). This phenomenon is attributed to the brackish-water conditions (i.e. low in sulfate) and the abundant input of reactive Fe(III) from the catchment, leading to a surplus of dissolved Fe2+ over dissolved sulfide in the sediment. The low availability of dissolved sulfide, in combination with the high average sedimentation rate, limits the formation of intermediate reduced sulfur compounds at the water–sediment interface, thereby retarding the conversion of FeS into pyrite (ratios of pyrite-S to AVS=0.17–1.73, median=0.37; degree of pyritization=1–17%, median=3%). Iron XAS, in combination with wavelet transform analysis, of representative sediment segments from the upper and lower mud units suggests that the non-sulfidized Fe(II) pool is dominantly complexed by organic matter, with the remaining Fe(II) occurring as mackinawite. This has implications for the understanding of early Fe diagenesis in settings with a high input of organic matter and relatively low supply of sulfate.

The placental sulfate transporter, Slc13a4, is critical for skeletal development in mice.

The placental sulfate transporter, Slc13a4, is critical for skeletal development in mice.

Changes of Photosynthesis-Related Parameters and Productivity of Spring Oilseed Rape under Different Nitrogen and Sulphur Fertilizers Supply

Fertilization with essential mineral elements is important to get high quality yield results. The lack of necessary mineral elements in soil can affect oilseed rape plant physiological functions, photosynthesis and plant productivity. Oilseed rape plants have high requirements for nitrogen and as oil crop – for sulphur. The aim of the investigation was to explain changes of chlorophyll a fluorescence parameters in spring oilseed rape leaves and yield changes under nitrogen and sulphur supply. During laboratory experiments changes of chlorophyll a fluorescence parameters and during field experiments changes of yield parameters under different nitrogen and sulphur supply were observed. Laboratory and field experiments showed that sulphur fertilizer rate 18 kg ha-1 is the most effective sulphur dose for spring oilseed rape, when nitrogen 55 kg ha-1 is added, because its presence has positive effect on photosynthetic reactions. There was found out in laboratory experiments that chlorophyll a fluorescence parameters Fv/Fm and PI can be used to describe sulphur and nitrogen mineral element supply efficacy on spring oilseed rape. There was observed in the field experiment that oilseed rape yield increases significantly (from +0.34 t ha-1 to +0.64 t ha-1) under optimal (S18N55) nutrient supply, but lack of sulphur leads to significant yield losses. To avoid excessive fertilizer usage, its negative impact on plant physiology and yield losses, we consider that sulphur: nitrogen = 1:3 as additional fertilizer is optimal for spring oilseed rape plants.

Enhanced microbial activity in carbon-rich pillow lavas, Ordovician, Great Britain and Ireland

There is extensive evidence for the microbial colonization of seafloor basalts in the modern ocean and in the geological record. The sulfur isotope composition of pyrite in the basalts commonly indicates marked isotopic fractionation due to microbial sulfate reduction. Sections through the Nemagraptus gracilis zone (Ordovician) in Great Britain and Ireland are characterized by both widespread pillow lavas and organic-rich seafloor sediment, allowing an exceptional opportunity to assess whether the availability of organic carbon influenced the extent of microbial activity in the basalts in deep geological time. Whole-rock data from basalts at 10 localities show that there is a relationship between sulfur isotopic composition and the carbon content of the basalt. At two localities where organic carbon was entrained in the basalt, isotopic compositions are heavy compared to compositions in carbon-poor basalt, implying that microbial activity exhausted the supply of seawater sulfate. In most basalt, microbial activity was limited by the supply of carbon, but where the basalt incorporated carbon during emplacement on the seafloor, microbial activity became sulfate limited.

N-acetylcysteine treatment ameliorates the skeletal phenotype of a mouse model of diastrophic dysplasia.

Diastrophic dysplasia (DTD) is a recessive chondrodysplasia caused by mutations in SLC26A2, a cell membrane sulfate-chloride antiporter. Sulfate uptake impairment results in low cytosolic sulfate, leading to cartilage proteoglycan (PG) undersulfation. In this work, we used the dtd mouse model to study the role of N-acetyl-l-cysteine (NAC), a well-known drug with antioxidant properties, as an intracellular sulfate source for macromolecular sulfation. Because of the important pre-natal phase of skeletal development and growth, we administered 30 g/l NAC in the drinking water to pregnant mice to explore a possible transplacental effect on the fetuses. When cartilage PG sulfation was evaluated by high-performance liquid chromatography disaccharide analysis in dtd newborn mice, a marked increase in PG sulfation was observed in newborns from NAC-treated pregnancies when compared with the placebo group. Morphometric studies of the femur, tibia and ilium after skeletal staining with alcian blue and alizarin red indicated a partial rescue of abnormal bone morphology in dtd newborns from treated females, compared with pups from untreated females. The beneficial effect of increased macromolecular sulfation was confirmed by chondrocyte proliferation studies in cryosections of the tibial epiphysis by proliferating cell nuclear antigen immunohistochemistry: the percentage of proliferating cells, significantly reduced in the placebo group, reached normal values in dtd newborns from NAC-treated females. In conclusion, NAC is a useful source of sulfate for macromolecular sulfation in vivo when extracellular sulfate supply is reduced, confirming the potential of therapeutic approaches with thiol compounds to improve skeletal deformity and short stature in human DTD and related disorders.

Crustal fluid and ash alteration impacts on the biosphere of Shikoku Basin sediments, Nankai Trough, Japan.

We present data from sediment cores collected from IODP Site C0012 in the Shikoku Basin. Our site lies at the Nankai Trough, just prior to subduction of the 19 Ma Philippine Sea plate. Our data indicate that the sedimentary package is undergoing multiple routes of electron transport and that these differing pathways for oxidant supply generate a complex array of metabolic routes and microbial communities involved in carbon cycling. Numerical simulations matched to pore water data document that Ca(2+) and Cl(1-) are largely supplied via diffusion from a high-salinity (44.5 psu) basement fluid, which supports the presence of halophile Archean communities within the deep sedimentary package that are not observed in shallow sediments. Sulfate supply from basement supports anaerobic oxidation of methane (AOM) at a rate of ~0.2 pmol cm(-3) day(-1) at ~400 mbsf. We also note the disappearance of δ-Proteobacteria at 434 mbsf, coincident with the maximum in methane concentration, and their reappearance at 463 mbsf, coinciding with the observed deeper increase in sulfate concentration toward the basement. We did not, however, find ANME representatives in any of the samples analyzed (from 340 to 463 mbsf). The lack of ANME may be due to an overshadowing effect from the more dominant archaeal phylotypes or may indicate involvement of unknown groups of archaea in AOM (i.e., unclassified Euryarchaeota). In addition to the supply of sulfate from a basement aquifer, the deep biosphere at this site is also influenced by an elevated supply of reactive iron (up to 143 μmol g(-1)) and manganese (up to 20 μmol g(-1)). The effect of these metal oxides on the sulfur cycle is inferred from an accompanying sulfur isotope fractionation much smaller than expected from traditional sulfate-reducing pathways. The detection of the manganese- and iron-reducer γ-Proteobacteria Alteromonas at 367 mbsf is consistent with these geochemical inferences.