Elke Mareke Bloem

Expression profiling of metabolic genes in response to methyl jasmonate reveals regulation of genes of primary and secondary sulfur-related pathways in Arabidopsis thaliana

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.

Influence of Sulfur Fertilization on Infection of Potato Tubers with Rhizoctonia solani and Streptomyces scabies

ABSTRACT Under conditions of sulfur (S)-deficient soil, applied S fertilization had a significant repressive effect on fungal infections such as that of oilseed rape and grapes with light leaf spot (Pyrenopeziza brassicae) and powdery mildew (Uncinula necator), respectively. For potatoes (Solanum tuberosum L.) it has been shown in earlier literature that elemental sulfur fertilization increased yield of potato tubers and improved tuber quality and resistance against Streptomyces scabies; the bactericidal effect was attributed to a reduced soil pH. So far, however, no information is available about the influence of S supply on bacterial and fungal diseases in potatoes. It was the aim of the present investigation to quantify the influence of S form and dose on infections of potato tubers with Rhizoctonia solani and Streptomyces scabies as a contribution to plant nutrition strategies for healthier plants. Field experiments with potatoes were conducted in 2001 and 2002 in Poland in a split-plot design with different sulfur forms (elemental S and K2SO4) and rates (0, 25, and 50 kg ha− 1 S). The application of sulfur significantly increased tuber yield in both years of experimentation. Generally, with increasing sulfur dose a significant decrease of the infection rate with Rhizoctonia solani was found for elemental S as well as for K2SO4 applications. Infection rate and severity of the disease was improved only by elemental S application due to a reduction in soil pH in the case of Streptomyces scabies. Thus it can be concluded that the health-promoting effect of sulfur fertilization was related mainly to the S status of the plant in case of infections with Rhizoctonia solani, while for Streptomyces scabies no mechanisms of S-induced resistance were found. The identification of differences in the S metabolism of Rhizoctonia solani and Streptomyces scabies may therefore elucidate S-induced resistance mechanisms in plants.

Significance of Sulfur Compounds in the Protection of Plants Against Pests and Diseases

ABSTRACT The effectiveness of targeted nutrition in the protection of plants against pests and diseases is called nutrient-induced resistance. Though the significance of individual nutrients for maintaining or promoting plant health prompted some interest in the 1960s and 1970s, research in the field of nutrient-induced resistance mechanisms has been scarce because of its complexity and limited practical significance due to the availability of effective pesticides. Interactions between mineral elements and plant diseases are well known for essential macro and micro plant nutrients, as well as aluminum and silicone. In the case of sulfur (S), the fungicidal effect of foliar-applied S has been exploited since the end of the 19th century, while the significance of soil-applied S for disease resistance became evident only a century later. Sulfur was neglected for a long time as an important plant nutrient because it was the main constituent of the toxic acid rain. Only during the 1990s, when S deficiency developed into a widespread nutrient disorder after clean air legislation came into force, was S also investigated with respect to nutritional aspects and plant health. Understanding the mechanisms of nutrient-induced resistance will contribute substantially to maintaining plant health in organic farming and minimize the input of pesticides in conventional farming systems. Sulfur-containing metabolites that are supposed to be involved in pathogen resistance are glutathione, glucosinolates, the gaseous release of volatile S, phytoalexins, S-rich proteins, and the formation of elemental S. Current knowledge about the influence of S nutritional status on these metabolites and their relationship to pathogenesis is summarized and discussed in the present article.

Influence of Nitrogen and Sulfur Fertilization on the Alliin Content of Onions and Garlic

Abstract Onion (Allium cepa L.) and garlic (Allium sativum L.) were among the earliest cultivated crops and have been popular in folk medicine for centuries. Alliins (cysteine sulfoxides) are the characteristic sulfur (S) containing secondary metabolites of Allium species like onions, shallot, garlic, leek and chives and they cause taste and sharpness and are criteria for the pharmaceutical quality. The influence of the S nutritional status on the content of secondary S containing metabolites was shown for different crops such as oilseed rape, mustard, nasturtium, and allium species. It was the aim of this study to investigate the influence of the S and nitrogen (N) supply on the alliin content of onion and garlic and to evaluate the significance for crop quality. In a greenhouse experiment three levels of N and S were applied in factorial combinations of 0, 50, and 250 mg pot−1 S and 250, 500, and 1000 mg pot−1 N. 8 plants were grown in a Mitscherlich pot containing 8 kg sand. Leaves and bulbs were sampled twice during the growth period in order to follow up translocation processes. The first sampling was carried out when leaves were developed, but bulb growth had not yet started and the second one during main bulb growth. An increasing S supply was related to an increasing alliin content in leaves and bulbs of both crops, whereas nitrogen fertilization had only a minor influence. The alliin content in bulbs could be doubled by S fertilization. A translocation of alliin from leaves to bulbs was found so that time of harvest has a strong influence on the alliin content. At the beginning of plant development high alliin contents were found in leaves, while with bulb development they were translocated into this plant organ. The results show that the potential health benefits of Allium species could be distinctly improved by S fertilization.

Short note: Runoff mapping using WEPP erosion model and GIS tools

Soil erosion, associated with environmental impacts and crop productivity loss, is usually considered the most impacting of surface hydrology processes. Runoff plays a major role in the erosion process, but it is also important by itself as it directly influences several surface hydrologic processes. In this paper, a computer interface (Erosion Database Interface, EDI) is described that allows processing the surface hydrology output database of the Water Erosion Prediction Project (WEPP) erosion prediction model, resulting in a georeferenced estimation of runoff. WEPP output contains non-georeferenced daily information about estimated runoff at the lower end of each Overland Flow Element. EDI, when running with WEPP, allows extracting WEPP-calculated runoff values, transforming them into annual means and relocating them in a georeferenced database readable by Geographic Information Systems (GIS). EDI was applied to a 1990ha watershed in southeast Brazil, with vegetation of mainly sugarcane, forest, and pasture. A 100-year climate simulation was used as input to WEPP, and erosion values were calculated at about six points per hectare and interpolated to a raster format. EDI was successful in preparing the database for automatic calculation of erosion and hydrologic parameters with WEPP and to restore georeferences to mean annual accumulated runoff data that were imported in the GIS as a vector database. Of all the resulting maps, the runoff map is the one that integrates all of the input parameters required for WEPP simulation, thus reflecting not only the physical environment but also crop growth and management and tillage operations. A very small correlation between runoff and erosion shows them to behave independently. Moreover, it is concluded that on analyzing runoff related to agricultural management, georeferenced runoff studies are especially important. In this context, EDI may be a useful tool to assess the effect of tillage and crop management on runoff production.

High resolution imaging of subcellular glutathione concentrations by quantitative immunoelectron microscopy in different leaf areas of Arabidopsis.

Highlights ► Determination of subcellular glutathione concentrations in different Arabidopsis leaf areas. ► Measurement of cell volumes and glutathione gold particle density by TEM. ► Glutathione concentrations of up to 15 mM were calculated for mitochondria. ► Main differences of glutathione contents between the leaf areas in vacuoles and mitochondria.

Sulfur Fertilization and Fungal Infections Affect the Exchange of H2S and COS from Agricultural Crops

The emission of gaseous sulfur (S) compounds by plants is related to several factors, such as the plant S status or fungal infection. Hydrogen sulfide (H(2)S) is either released or taken up by the plant depending on the ambient air concentration and the plant demand for S. On the contrary, carbonyl sulfide (COS) is normally taken up by plants. In a greenhouse experiment, the dependence of H(2)S and COS exchange with ambient air on the S status of oilseed rape (Brassica napus L.) and on fungal infection with Sclerotinia sclerotiorum was investigated. Thiol contents were determined to understand their influence on the exchange of gaseous S compounds. The experiment revealed that H(2)S emissions were closely related to pathogen infections as well as to S nutrition. S fertilization caused a change from H(2)S consumption by S-deficient oilseed rape plants to a H(2)S release of 41 pg g(-1) (dw) min(-1) after the addition of 250 mg of S per pot. Fungal infection caused an even stronger increase of H(2)S emissions with a maximum of 1842 pg g(-1) (dw) min(-1) 2 days after infection. Healthy oilseed rape plants acted as a sink for COS. Fungal infection caused a shift from COS uptake to COS releases. The release of S-containing gases thus seems to be part of the response to fungal infection. The roles the S-containing gases may play in this response are discussed.

SPATIAL AND TEMPORAL VARIABILITY OF SULPHATE CONCENTRATION IN SOILS

The mobility of soil sulphate is high on agricultural sites with soil pH values of higher than 5 due to a low adsorption capacity. Under humid conditions, the variability of soil texture and hydrological soil properties resulted in a high fluctuation of soil sulphate content within space and time. Investigations into the spatial variability of soil sulphate produce a coefficient of variation of the soil sulphate content between 15 and 100% at different soil depths, with the highest variation present in the deeper soil layers. The results of the geostatistical analysis indicate that a sampling distance of not more than 25 m is required to determine spatially correlated values. No correlation between the sulphate content of the soil and the total S status of cereals was determined from grid sampling on two sites in northern Germany, indicating that soil analysis of sulphate was not an appropriate method for the prognosis of the sulphur nutritional status. The variability of the soil sulphate content in space and time was too high to show a relationship with the less variable plant tissue contents.

Milestones in plant sulfur research on sulfur-induced-resistance (SIR) in Europe

Until the 1970s of the last century sulfur (S) was mainly regarded as a pollutant being the main contributor of acid rain, causing forest dieback in central Europe. When Clean Air Acts came into force at the start of the 1980s SO2 contaminations in the air were consequently reduced within the next years. S changed from an unwanted pollutant into a lacking plant nutrient in agriculture since agricultural fields were no longer “fertilized” indirectly by industrial pollution. S deficiency was first noticed in Brassica crops that display an especially high S demand because of its content of S-containing secondary metabolites, the glucosinolates. In Scotland, where S depositions decreased even faster than in continental Europe, an increasing disease incidence with Pyrenopeziza brassicae was observed in oilseed rape in the beginning 1990s and the concept of sulfur-induced-resistance (SIR) was developed after a relationship between the S status and the disease incidence was uncovered. Since then a lot of research was carried out to unravel the background of SIR in the metabolism of agricultural crops and to identify metabolites, enzymes and reactions, which are potentially activated by the S metabolism to combat fungal pathogens. The S status of the crop is affecting many different plant features such as color and scent of flowers, pigments in leaves, metabolite concentrations and the release of gaseous S compounds which are directly influencing the desirability of a crop for a variety of different organisms from microorganisms, over insects and slugs to the point of grazing animals. The present paper is an attempt to sum up the knowledge about the effect of the S nutritional status of agricultural crops on parameters that are directly related to their health status and by this to SIR. Milestones in SIR research are compiled, open questions are addressed and future projections were developed.

Influence of Fertilizer Practices on S-Containing Metabolites in Garlic (Allium sativum L.) under Field Conditions

Cysteine sulfoxides (e.g., alliin) are the characteristic sulfur-containing secondary compounds in garlic, which account for taste and pharmaceutical quality. It was the aim of the present study to investigate the influence of sulfur and nitrogen supply under field conditions on the alliin content and cysteine and glutathione as possible precursors. Sulfur and nitrogen were applied in four different rates, and five samplings were conducted. Sulfur fertilization significantly increased the cysteine, glutathione, and alliin contents of leaves and bulbs, while nitrogen fertilization had no significant influence. Cysteine increased by a factor of 1.3-1.5 in leaves and 1.0-2.0 in bulbs. Glutathione increased significantly in bulbs by a factor of 0.9-1.6 but only at main growth and not at maturity. The alliin concentration in bulbs increased with S fertilization significantly at all harvesting dates and at maturity from 5.1 to 11.2 mg g(-1) of dry weight. High sulfur application in combination with low nitrogen fertilization increased the alliin concentration in garlic significantly during main growth until the beginning of ripening. At the last harvest, 15 kg ha(-1) S resulted in high-quality garlic suitable for consumption and use in plant protection or pharmaceutical industries.