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

Abstract

Until the 1970's 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 1980's 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 1990's 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.

Bryophyte gas‐exchange dynamics along varying hydration status reveal a significant carbonyl sulphide (COS) sink in the dark and COS source in the light

“…The existence of a bi‐directional COS flux contradicts our initial expectation for COS uptake by astomatous bryophytes, because there are currently no described leaf‐level processes that result in COS as a byproduct (Protoschill‐Krebs et al ., 1996; Bloem et al ., 2015). Previously, Fried et al .…”

“…COS diffuses into the vegetation through the stomatal pores and is hydrolysed by the enzyme carbonic anhydrase (CA) in the mesophyll cells (Protoschill‐Krebs et al ., 1996). However, in contrast to CO 2 hydration by CA, COS hydrolysis by CA is irreversible (Notni et al ., 2007) and no other leaf‐level processes have been identified in the production of COS (Bloem et al ., 2015). Thus, COS uptake ( A S ) is assumed to be unidirectional and not the net result of two opposed fluxes (photosynthesis and respiration in the case of CO 2 ).…”

Bioassimilable sulphur provides effective control of Oidium neolycopersici in tomato, enhancing the plant immune system

“…However, our results showed better protection against O. neolycopersici when the compound was applied as a preventive soil drench, suggesting that the protective effect of the bioassimilable sulphur may be related to the induction of plant defences. Previous studies have suggested that the application of sulphur can improve the natural resistance of plants against fungal pathogens through the stimulation of metabolic processes that involve S 0 , resulting in so‐called sulphur‐induced resistance (SIR) …”

“…Previous studies have suggested that the application of sulphur can improve the natural resistance of plants against fungal pathogens through the stimulation of metabolic processes that involve S 0 , resulting in so-called sulphur-induced resistance (SIR). 20 Callose accumulation is a characteristic cellular response of early post-invasive defences that prevents the colonisation of the pathogen by creating a physical barrier at the site of the infection. This barrier is able to slow pathogen invasion in the attacked tissue, giving more time to activate additional defence responses that may require gene activation and expression.…”

Increase of chromium tolerance in Scenedesmus acutus after sulfur starvation: Chromium uptake and compartmentalization in two strains with different sensitivities to Cr(VI)

“…(Cobbett, 2000;Cobbett and Goldsbrough, 2002), and reduced glutathione (GSH) involved in both metal chelation and in scavenging potential oxidative stress as a result of ROS production induced by Cr exposure ( Grill et al 2004;Panda, 2007;Upadhyay andPanda, 2010, Volland et al 2011). Hence sulfur availability can lead to an increased capacity to cope with biotic and abiotic stresses, a phenomenon known as SIR/SED (Sulfur Induced Resistance or Sulfur Enhanced Defence) (Bloem et al 2015;Ernst et al 2008;Höller et al 2010;Nazar et al 2011;Nocito et al 2006). Although a few reports suggest the involvement of PCs or MTs in Cr detoxification (Diwan et al 2010;Shanker et al 2004), two direct products of sulfur assimilation pathway other than PCs or MTs can be involved in chromium detoxification, since the metal can be sequestered through the formation of thiolate and cysteinthiolate complexes with glutathione and various derivatives of cysteine (Brauer et al 1996;Brauer and Wetterhahn, 1991).…”