Derivatives with insertional inactivation of prqA and mvrA genes were obtained and studied in the Synechocystis sp. PCC6803 wild-type strain and in the mutant Prq20 resistant to methyl viologen (MV). It was shown that the formation of resistance to MV is associated with the operation of two systems: constitutive and inducible. The prqA gene encoding drug efflux proteins controls the constitutive system of cell resistance to MV. Derepression of the prqA gene is the main reason for an enhanced MV resistance in the Prq20 mutant with impaired repressor function of the PrqR protein. The mvrA gene encoding the transmembrane protein from the family of transporters of sugar and other compounds controls the inducible MV resistance. It is assumed that the MvrA protein is required for efficient elimination from cells of toxic substances formed upon oxidative stress or participates in the repair of membranes destroyed by oxidants. The data obtained demonstrated for the first time that transport systems are involved in the formation of MV resistance in photosynthetic organisms.