A new phenotype for a herbicide resistant mutant of Synechocystis 6714 with a high sensitivity to photoinhibition

In this article, we describe the genotype and phenotype of a double mutant of Synechocystis PCC 6714 carrying A251V and S264A mutations in the Q(B) pocket of the D-1 protein. The mutation A251V confers an increased sensitivity to high light on the Photosystem II (PS II). The A251V mutation also results in a modification of electron transfer between Q(A)(-) and Q(B), a destabilization of the S(2)Q(B)(-) State and a destabilization of the S-1 state due to a better accessibility of the oxygen evolving complex to cytosolic reductants. The double mutant is more sensitive to high light than the simple mutant. The electron transfer between Q(A)(-) and Q(B) is modified in both mutants. In contrast to the single mutant, in the A251V, S264A mutant, the S(2)Q(B)(-) and the S(2)Q(A)(-) states are stabilized and there are no modifications on the donor side of the Photosystem II. We conclude that there is no direct relationship between the S-1 destabilization and the increased sensitivity to high light. The correlation between the sensitivity of the PS II to high light and Q(A)(-), Q(B)(-) stabilities is also uncertain.