RNA helicase, CrhR is indispensable for the energy redistribution and the regulation of photosystem stoichiometry at low temperature in Synechocystis sp. PCC6803

► Redox of PQ-downstream e- carriers signals psaAB expression at low temperature (LT). ► Synechocystis acclimatize to LT by controlling PS stoichiometry & State transitions. ► ΔcrhR unable to maintain PQ redox state & failed to operate state transitions at LT. ► In ΔcrhR, oxidized state of e- carriers leads to PSI genes down regulation at LT. ► CrhR is essential for state transitions & PS stoichiometry regulation at LT.