Publikationen - Molekulare Signalverarbeitung

Mutualistic symbioses between plant roots and microorganisms can reduce the demand for chemical fertilizers in agriculture. Most crops are able to establish arbuscular mycorrhiza (AM) symbiosis with fungi to take up phosphate more efficiently. A second symbiosis, nitrogen-fixing root nodule symbiosis, supersedes energy-intensive nitrogen fertilization: Legumes such as peas, clover and soybeans take up rhizobia – special bacteria that are capable of converting atmospheric nitrogen into ammonium – into their root cells. Plant root cells perceive rhizobia and AM fungi via very similar signaling molecules (N-acetylglucosamine tetra- or pentamers), even though the resultant developmental processes differ strongly. Interestingly, N-acetylglucosamine containing signals including fungal chitin- and bacterial peptidoglycan-fragments from their cell walls, also play a role in the recognition of pathogenic microorganisms.Despite the intrinsic sustainability potential of the nitrogen-fixing root nodule symbiosis, too much of a good thing, however, has led to global problems: The massive increase in global meat production is largely based on soybean. Large scale soybean monoculture destroyed ecosystems in South America. Large scale animal production results in excessive methane and nitrogen release into the environment, which causes climate change and death zones in marine ecosystems, respectively. This calls for a considerable reduction in meat consumption.

Plant secondary metabolites, also termed specialized plant metabolites, currently comprise more than 200 000 natural products that are all based on a few biosynthetic pathways and key primary metabolites. Some pathways like flavonoid and terpenoid biosynthesis are universally distributed in the plant kingdom, whereas others like alkaloid or cyanogenic glycoside biosynthesis are restricted to a limited set of taxa. Diversification is achieved by an array of mechanisms at the genetic and enzymatic level including gene duplications, substrate promiscuity of enzymes, cell‐specific regulatory systems, together with modularity and combinatorial aspects. Specialized metabolites reflect adaptations to a specific environment. The observed diversity illustrates the heterogeneity and multitude of ecological habitats and niches that plants have colonized so far and constitutes a reservoir of potential new metabolites that may provide adaptive advantage in the face of environmental changes. The code that connects the observed chemical diversity to this ecological diversity is largely unknown. One way to apprehend this diversity is to realize its tremendous plasticity and evolutionary potential. This chapter presents an overview of the most widespread and popular secondary metabolites, which provide a definite advantage to adapt to or to colonize a particular environment, making the boundary between the “primary” and the “secondary” old fashioned and blurry.

This chapter focuses on Ophioviridae family whose sole member genus is Ophiovirus. The member species of the genus include Citrus psorosis virus (CPsV), Freesia sneak virus(FreSV), Lettuce ring necrosis virus (LRNV), and Mirafiori lettuce big-vein virus (MiLBVV).The single stranded negative/possibly ambisense RNA genome is divided into 3–4 segments, each of which is encapsidated in a single coat protein (43–50 kDa) forming filamentous virions of about 3 nm in diameter, in shape of kinked or probably internally coiled circles of at least two different contour lengths. Ophioviruses can be mechanically transmitted to a limited range of test plants, inducing local lesions and systemic mottle. The natural hosts of CPsV, ranunculus white mottle virus (RWMV), MiLBVV, and LRNV are dicotyledonous plants of widely differing taxonomy. CPsV has a wide geographical distribution in citrus in the Americas, in the Mediterranean and in New Zealand. FreSV has been reported in two species of the family Ranunculacae from Northern Italy, and in lettuce in France and Germany. Tulip mild mottle mosaic virus (TMMMV) has been reported in tulips in Japan. LRNV is closely associated with lettuce ring necrosis disease in The Netherlands, Belgium, and France, and FreSV has been reported in Europe, Africa, North America and New Zealand.

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In plants, the oxylipin pathway gives rise to several oxygenated fatty acid derivatives such as hydroxy- and keto fatty acids as well as volatile aldehydes and cyclic compounds, which are, in part, physiologically active [1]. Among these, jasmonic acid is discussed as signalling molecule during several stress responses, wounding, senescense and plant pathogen interactions [2].