Alfonso M, Pueyo J J, Gaddour K, Etienne A L, Kirilovsky D, Picorel R
Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, Zaragoza, Spain.
Plant Physiol. 1996 Dec;112(4):1499-508. doi: 10.1104/pp.112.4.1499.
We have isolated several herbicide-resistant cell lines from photosynthetic cell suspensions of soybean (Glycine max) that possessed different levels of herbicide resistance, photosystem II activity, and chlorophyll a/b ratio. We have further studied the STR7 mutant, which showed 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). 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. To our knowledge, this substitution has not previously been described in any photosynthetic organism. In addition to affecting atrazine resistance, this single amino acid change caused 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 showed a larger antenna size, an increase in non-QB-reducing centers, and a higher sensitivity to light stress. The unusual stability of the S2QB- and S3QB- states indicates that STR7 belongs to a new class of QB-site mutants.
我们已从大豆（Glycine max）光合细胞悬浮液中分离出几种抗除草剂细胞系，这些细胞系具有不同水平的除草剂抗性、光系统II活性和叶绿素a/b比值。我们进一步研究了STR7突变体，它对莠去津表现出最高水平的抗性，并且对3-(3,4-二氯苯基)-1,1-二甲基脲具有交叉抗性（与野生型相比，分别为50倍和3倍）。对该突变体的psbA基因（编码光系统II的D1多肽）进行测序，结果显示D1蛋白中有一个单一变化，即丝氨酸-268突变为脯氨酸。据我们所知，这种取代此前在任何光合生物中均未被描述过。除了影响莠去津抗性外，这一单氨基酸变化还导致次级受体QA和QB之间电子传递速率降低，以及S2QB-和S3QB-状态的稳定。该突变体还表现出更大的天线尺寸、非QB还原中心增加以及对光胁迫更高的敏感性。S2QB-和S3QB-状态的异常稳定性表明STR7属于一类新的QB位点突变体。
