Induced new mutation of D1 serine-268 in soybean photosynthetic cell cultures produced atrazine resistance, increased stability of S2QB- and S3QB- states, and increased sensitivity to light stress.

摘要

Several herbicide-resistant cell lines were isolated from photosynthetic cell suspensions of soyabean cv. Corsoy with different levels of herbicide resistance, photosystem II activity, and chlorophyll a/b ratio. In addition, the STR7 mutant, which exhibits the highest level of resistance to atrazine as well as a cross-resistance to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (50- and 3-fold, respectively, compared with the wild type), was further investigated. Sequencing of the psbA gene (coding for the D1 polypeptide of photosystem II) from this mutant revealed a single change, serine-268 to proline, in the D1 protein, which has not previously been described in any photosynthetic organism. In addition to affecting atrazine resistance, this single amino acid change resulted in a decrease in the electron transfer rate between the secondary acceptors QA and QB and a stabilization of the S2QB- and S3QB- states. The mutant also exhibited a larger antenna size, an increase in non-QB-reducing centres, anda higher sensitivity to light stress. It is suggested that the unusual stability of the S2QB- and S3QB- states indicates that STR7 may belong to a new class of QB-site mutants.