Ajlani G, Kirilovsky D, Picaud M, Astier C
UPR 407, CNRS, Gif sur Yvette, France.
Plant Mol Biol. 1989 Nov;13(5):469-79. doi: 10.1007/BF00027307.
Mutations conferring herbicide resistance in 3 mutant strains of the cyanobacterium Synechocystis 6714 have been characterized by gene cloning and sequencing. The mutants display very different phenotypes: DCMU-IIA is DCMU-resistant and atrazine-resistant, DCMU-IIB is DCMU-resistant and atrazine-sensitive, and Az-V is DCMU-sensitive, atrazine-resistant and presents particular photoinhibition properties. These mutants were originally obtained either by one-step selection (DCMU-IIA) or by two-step selection (DCMU-IIB and Az-V). psbA copies carrying herbicide resistance have been identified by transformation experiments as psb AI in all cases. Sequences of the psb AI copy of each mutant have been compared to the wild-type sequence. In the single mutant DCMU-IIA, a point mutation at codon 264 (Ser----Ala) results in resistance to both DCMU and atrazine. In the double mutants DCMU-IIB and Az-V, two point mutations were found. DCMU-IIB was derived from DCMU-IIA and had acquired a second mutation at codon 255 (Phe----Leu) resulting in a slight increase in DCMU resistance and complete abolition of atrazine resistance. Az-V contains two changes at codons 211 (Phe----Ser) and 251 (Ala----Val) resulting in high atrazine resistance but only slight DCMU resistance.
通过基因克隆和测序对集胞藻6714的3个突变株中赋予除草剂抗性的突变进行了表征。这些突变株表现出非常不同的表型：DCMU-IIA对DCMU和莠去津均具有抗性，DCMU-IIB对DCMU具有抗性但对莠去津敏感，而Az-V对DCMU敏感、对莠去津具有抗性并呈现出特殊的光抑制特性。这些突变株最初是通过一步筛选（DCMU-IIA）或两步筛选（DCMU-IIB和Az-V）获得的。通过转化实验已确定在所有情况下携带除草剂抗性的psbA拷贝均为psbAI。已将每个突变株的psbAI拷贝序列与野生型序列进行了比较。在单突变株DCMU-IIA中，第264位密码子处的点突变（丝氨酸→丙氨酸）导致对DCMU和莠去津均具有抗性。在双突变株DCMU-IIB和Az-V中，发现了两个点突变。DCMU-IIB源自DCMU-IIA，并在第255位密码子处获得了第二个突变（苯丙氨酸→亮氨酸），导致DCMU抗性略有增加，莠去津抗性完全丧失。Az-V在第211位（苯丙氨酸→丝氨酸）和第251位（丙氨酸→缬氨酸）密码子处有两个变化，导致对莠去津具有高抗性，但对DCMU仅具有轻微抗性。
