Oligogalacturonides and chitosan activate plant defensive genes through the octadecanoid pathway.

Jasmonic acid, synthesized from linolenic acid (the octadecanoid pathway), has been proposed to be part of a signal transduction pathway that mediates the induction of defensive genes in plants in response to oligouronide and polypeptide signals generated by insect and pathogen attacks. We report here that the induction of proteinase inhibitor accumulation in tomato leaves by plant-derived oligogalacturonides and fungal-derived chitosan oligosaccharides is severely reduced by two inhibitors (salicylic acid and diethyldi-thiocarbamic acid) of the octadecanoid pathway, supporting a role for the pathway in signaling by oligosaccharides. Jasmonic acid levels in leaves of tomato plants increased several fold within 2 hr after supplying the polypeptide systemin, oligogalacturonides, or chitosan to the plants through their cut stems, as expected if they utilize the octadecanoid pathway. The time course of jasmonic acid accumulation in tomato leaves in response to wounding was consistent with its proposed role in signaling proteinase inhibitor mRNA and protein synthesis. The cumulative evidence supports a model for the activation of defensive genes in plants in response to insect and pathogen attacks in which various elicitors generated at the attack sites activate the octadecanoid pathway via different recognition events to induce the expression of defensive genes in local and distal tissues of the plants.

Role of phosphorylation in elicitation of the oxidative burst in cultured soybean cells.

The oxidative burst is likely the most rapid defense response mounted by a plant under pathogen attack, and the generated oxidant species may be essential to several subsequent defense responses. In our effort to characterize the signal-transduction pathways leading to rapid H2O2/O2- biosynthesis, we have examined the role of protein phosphorylation in this resistance mechanism. K-252a and staurosporine, two protein-kinase inhibitors, were found to block the oxidative burst in a concentration-dependent manner. When added during H2O2 generation, the burst was observed to rapidly terminate, suggesting that continuous phosphorylation was essential for its maintenance. Importantly, phosphatase inhibitors (calyculin A and okadaic acid) were found to induce the oxidative burst in the absence of any additional stimulus. This may suggest that certain kinases required for the burst are constitutively active and that stabilization of the phosphorylated forms of their substrates is all that is required for burst activity. In autoradiographs of elicited and unstimulated cells equilibrated with 32PO4(3-), several phosphorylated polypeptide bands were revealed that could represent proteins essential for the burst.

Induction, modification, and transduction of the salicylic acid signal in plant defense responses.

Studies in our laboratory as well as others strongly suggest that salicylic acid (SA) plays an important signaling role in plant defense against pathogens. We have found that increases in endogenous SA levels correlates with both resistance of tobacco to infection with tobacco mosaic virus and induction of defense-related genes such as that encoding pathogenesis-related protein 1 (PR-1). Some of this newly synthesized SA was conjugated to glucose to form SA beta-glucoside. A cell wall-associated beta-glucosidase activity that releases SA from this glucoside has been identified, suggesting that SA beta-glucoside serves as an inactive storage form of SA. By purifying a soluble SA-binding protein and isolating its encoding cDNA from tobacco, we have been able to further characterize the mechanism of SA signaling. This protein is a catalase, and binding of SA and its biologically active analogues inhibited catalase's ability to convert H2O2 to O2 and H2O. The resulting elevated levels of cellular H2O2 appeared to induce PR-1 gene expression, perhaps by acting as a second messenger. Additionally, transgenic tobacco expressing an antisense copy of the catalase gene and exhibiting depressed levels of catalase also showed constitutive expression of PR-1 genes. To further dissect the SA signaling pathway, we have tested several abiotic inducers of PR gene expression and disease resistance for their ability to stimulate SA production. Levels of SA and its glucoside rose following application of all of the inducers except 2,6-dichloroisonicotinic acid. 2,6-Dichloroisonicotinic acid was found to bind catalase directly and inhibit its enzymatic activity. Thus, it appears that many compounds that induce PR gene expression and disease resistance in plants inactivate catalases directly or indirectly.

Use of Arabidopsis thaliana defense-related mutants to dissect the plant response to pathogens.

The plant defense response to microbial pathogens had been studied primarily by using biochemical and physiological techniques. Recently, several laboratories have developed a variety of pathosystems utilizing Arabidopsis thaliana as a model host so that genetic analysis could also be used to study plant defense responses. Utilizing a pathosystem that involves the infection of Arabidopsis with pathogenic pseudomonads, we have cloned the Arabidopsis disease-resistance gene RPS2, which corresponds to the avirulence gene avrRpt2 in a gene-for-gene relationship. RPS2 encodes a 105-kDa protein containing a leucine zipper, a nucleotide binding site, and 14 imperfect leucine-rich repeats. The RPS2 protein is remarkably similar to the product of the tobacco N gene, which confers resistance to tobacco mosaic virus. We have also isolated a series of Arabidopsis mutants that synthesize decreased levels of an Arabidopsis phytoalexin called camalexin. Analysis of these mutants indicated that camalexin does not play a significant role in limiting growth of avirulent Pseudomonas syringae strains during the hypersensitive defense response but that it may play a role in limiting the growth of virulent strains. More generally, we have shown that we can utilize Arabidopsis to systematically dissect the defense response by isolation and characterization of appropriate defense-related mutants.

Effects of landscape spatial heterogeneity on dryland restoration success. The combined role of site conditions and reforestation techniques in southeastern Spain

In occidental Europe, Spain is one of countries the most severely affected by desertification (Arnalds & Arsher 2000). Particularly, South-eastern Spain is considered as one of the most threatened areas by desertification in Mediterranean Europe (Vallejo 1997). In 2003, the Valencia Regional Forest Service implemented a restoration demonstration project in this area. The project site is a small catchment (25 ha) located in the Albatera municipality. The catchment is highly heterogeneous, with terraced slopes, south-facing slopes and north-facing slopes. The restoration strategy was based on planting evergreen trees and shrubs which can grow quickly after disturbances, and on field treatments aimed at maximizing water collection (micro-catchments, planting furrows), organic amendment (compost), and conservation (tree shelters, mulching). On south landscape unit, the whole category of restoration treatments was applied: water micro-catchment + Tubex tree shelters + mulching & compost, while on north landscape unit: netting tree shelters + mulching & compost only were applied, while in terrace landscape unit: furrows + netting tree shelters + mulching & compost were applied. Survival and growth of the planted seedlings were used as metrics of restoration success. To assess the effects of the treatments applied for soil conservation, soil loss rates (from 2005 to 2009) were evaluated using the erosion pin method. We conclude that, despite the limiting conditions prevailing on the south unit, this landscape unit showed the highest survival and growth plant rates in the area. The best seedling performances on the south landscape unit were probably due to the highest technical efforts applied, consisting in the water micro-catchment installation and the Tubex plant shelters addition. In addition, soil loss rates followed decreasing trends throughout the assessment period. Soil loss rates were highest on south landscape unit in comparison with the other landscape units, due to the more accentuated relief. North landscape unit and terrace unit showed a net soil mass gain, probably reflecting the trapping of sediments produced by plantation works.

The future of the Eurozone and the role of the German Constitutional Court. Research Papers in Law, 05/2012

[Introduction.] Necessary reforms towards a deepened and increased European shaped economic, financial and budgetary policy, paraphrased with the term “fiscal union”, could possibly reach constitutional limits. In its EFSF judgment1, the German Constitutional Court, following the Lisbon judgment in which certain government tasks were determined as being part of the “constitutional identity”2, connected the budget right of the parliament via the principle of democracy to the eternity clause of Art. 79 para 3 Basic Law. A transfer of essential parts of the budget right of the German Bundestag, which would be in conflict with the German constitution, is said to exist when the determination of the nature and amount of the tax affecting the citizens is largely regulated on the supranational level and thereby deprived of the Bundestag’s right to disposition. A reform of the Economic and Monetary Union that touches the core of the budget right can, according to the German Federal Court, with regard to Art. 79 (3) of the Basic Law only be realized by way of Art. 146 of the Basic Law, thus with a new constitution given by the people that replaces the Basic Law.3

The fiscal compact - Europe's "hard core" based on German economic conditions. OSW Commentary No. 71, 2012-03-07

On 2 March, the leaders of 25 EU member states signed the Treaty on stability, coordination and governance in the economic and monetary union. It will introduce new fiscal constraints and officially vest new competences in the eurozone countries. Thus, their right to coordinate economic policy among them will be sanctioned. So far, the Lisbon Treaty has only provided for organisation of informal Eurogroup meetings, to be attended by representatives of the European Commission. The principles introduced by the compact, if the eurozone countries are really determined to observe its provisions, will create a new way of managing the single currency. Within the next few years, the most indebted countries will have to carry out radical reforms to boost their competitiveness and adjust it to German standards. During this period the Federal Republic of Germany will most probably decide to offer higher loan guarantees to relieve these countries’ budgets. The compact’s political consequences are also of great significance, especially considering how the treaty was finalised. The eurozone states have in fact accepted that the direction for changes will be devised by France and Germany, and the role of European institutions such as the Commission or the Parliament may weaken. From the perspective of eurozone candidate countries, the introduction of the fiscal compact means expanding the scope of conditions they must meet to become members of the single currency area. In the future, a country, in order to adopt the single currency, will have to meet the structural deficit criterion, and also most probably carry out economic reforms such as unifying its fiscal system. These goals will be achieved across the eurozone gradually, in the subsequent stages of the economic governance reform.

Current Account ‘Core-Periphery Dualism’ in the EMU. CEPS Working Document No. 406/March 2015

Current account dispersion within EU member states has been increasing since the 1990s. Interestingly, the persistent deficits in many peripheral countries have not been accompanied by a significant growth process that is able to stimulate a long-run rebalancing, as neoclassical theory predicts. To shed light on the issue this paper investigates the determinants of eurozone current account imbalances, focusing on the role played by financial integration. The analysis considers two samples of 22 OECD and 15 EU countries; three time horizons corresponding to various steps in European integration; different control variables; and several panel econometric methods. The results suggest that within the OECD and EU groups, financial integration helped to explain CA deterioration in the peripheral countries, especially in the post-EMU period. The business cycle seems to have played a growing role over time, whereas the role of competiveness seems to have diminished.