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Regulatory mechanisms in photosynthetic organisms

Cellular redox state and its influence in regulation mechanisms (P. Setif)

The research project "Cellular redox state" (Pierre Sétif) is focused on the study of cyanobacteria. Cyanobacterial physiology and growth depend on the cellular redox state which also plays a key regulator role.

Published on 23 October 2017

Pierre Sétif

We are studying the mechanisms involved in the modulation and regulation of this redox state, which mostly depends on photosynthetic and respiratory electron and proton flows. These processes are characterized in different species and many mutants and this knowledge is the basis for present and future developments of third generation biofuels.

Electron and proton flows (lines and arrows) and some in vivo observables (ovals).

The simultaneous presence of photosynthetic and respiratory complexes in the internal membranes of cyanobacteria is a challenging issue, as several modes of electron transfer (photosynthetic linear and cyclic, respiratory) are coexisting and strongly interacting. The two primary metabolites ATP and NADPH which are produced from these processes, are regulated in their relative amounts so as to adjust the ATP/NADPH ratio to cellular needs. Moreover, the defence mechanisms against ROS, which are inevitably produced during photosynthetic and respiratory electron flows, are studied in parallel.

Several spectroscopic probes provide real-time information on the in vivo electron flows. We are using these probes to determine the cellular redox state and to measure the rates of some essential reactions, in various physiological conditions (light intensity and wavelength, redox stress, nutrient deficiencies, inhibitors, etc...) and in many strains and mutants.

The same approaches are being extended to the study of eucaryotic microalgae and some essential electron transfer reactions are also studied in vitro with isolated proteins.