Life depends on homeostatic mechanisms that maintain the constant (bio-)chemical conditions in the cell needed for efficient growth, high yield, sustained health, undisturbed development and, in ecological terms, maximum fitness and competitiveness of plants, animals and humans.
On the cell level the optimum response to changing environmental conditions depends on a highly ordered and complex signal and information exchange system.
(1) Within this system, relevant signals are sensed first.
(2) The significance of the signals for the cell under the prevailing physical, chemical and biotic conditions is evaluated by integration with other information.
(3) The specifically released information is transmitted to targets that in turn
(4) enable the appropriate acclimation of the organism.
Among the exploited signals the reduction and oxidation (redox) state of the cell is of eminent importance for all organisms including plants, animals and humans. Redox signal perception and signal integration was the topic of the interdisciplinary workshop bringing together 88 scientists from the diverse science fields of molecular biology, genetics, cell biology, chemistry, medicine, plant sciences, physics, biomathematics and bioinformatics. Plants and animals have a common genetic and thus functional heritage that originates from an ancestral unicellular organism which was the predecessor of both evolutionary lineages. From the beginning of life, cells had to fight against environmental threats many of which cause imbalances in the cellular redox-state. Three billion years ago, the redox challenge increased with the enrichment of the atmosphere with oxygen as a consequence of the evolution of photosynthesis. The significance of redox imbalances becomes immediately obvious in the context of oxidative disorder causing severe harvest losses in agriculture and progression of human diseases such as neuronal disorders.
Various aspects of cellular redox signalling were addressed in 30 presentations by scientists from eight countries. The prevention of redox imbalances in green algae and plants was analyzed, e.g. by Jean-David Rochaix and Thomas Pfannschmidt who employ genetic approaches to pinpoint decisive novel elements in the regulatory process. The maintenance and restitution of redox homeostasis was the topic of a series of talks, e.g. by Yves Meyer, who showed considerable redundancy in the redox homeostasis system. Still novel elements are identified that are involved in detoxification of dangerous radicals, e.g. as outlined in the talks by Jean-Pierre Jacquot and Javier Cejudo. Detailed analysis of redox disorder was addressed by Bernard Knoops who described the function of human peroxiredoxin 5 in antioxidant defence and signalling. Exciting new insight into the beneficial effect of flavanol-rich diet on cell redox state was reported by Helmut Sies who showed that flavonoids that are contained in many legumes, fruits and green tea specifically interact with cell processes and slow down the release of reactive oxygen species in the cells.
In addition to the analysis of single components and processes our future comprehensive understanding of redox signal integration and the involved networks depends on the development and deployment of novel tools, e.g. genome-wide analyses of cell functions and modelling of pathways. Dirk Koschützki and Oliver Ebenhöh presented bioinformatics concepts to describe signalling networks and to identify the central elements. Frank van Breusegem, Hans Bohnert and Ron Mittler showed successful systematic approaches by use of transcript profiling to understand the redox signalling network.
The workshop with its presentations from diverse viewpoints and the vivid discussions among the participants showed that redox signalling networks represent a very important biological system suitable for a detailed systematic approach across the disciplinary borders. Systems' biology aims at a complete description and predictive modelling of biological processes. Analysis of subsystems will pave the way to more holistic approaches. To this end, the workshop summarized our present-day knowledge of redox signalling and provided perspectives on future developments to arrive at a complete understanding which is important, e.g. in order to increase stress tolerance of crop plants and to fight diseases in the future.