English J, Harrison K, Jones J D
Sainsbury Laboratory, John Innes Centre, Norwich, United Kingdom.
Plant Cell. 1993 May;5(5):501-14. doi: 10.1105/tpc.5.5.501.
Our objective was to test whether the double Ds structure correlated with Dissociation state I activity (i.e., high frequency of chromosome breakage and low frequency of reversion) in maize exhibited similar properties in tobacco. A genetic assay was established to test double Ds and related structures for their ability to cause loss of the linked marker genes streptomycin phosphotransferase and beta-glucuronidase in transgenic tobacco. An engineered double Ds element and a simple Ds element showed behavior consistent with that of state I and state II Ds elements, respectively, as described for maize. DNA structural rearrangements accompanied marker gene loss. Dissection of the double Ds structure showed that a left end and a right end of Ds in direct orientation were sufficient for the instability observed. This result suggested that left and right ends of Ds in direct orientation can participate in aberrant transposition events, consistent with two different models for double Ds-induced chromosome breakage proposed previously. Both models predict that the inversion of a half Ds element accompanies the aberrant transposition event. Such an inversion was detected by polymerase chain reaction experiments in tobacco and maize only when Activator activity was present in the genome.
我们的目标是测试玉米中与解离状态I活性（即染色体高断裂频率和低回复频率）相关的双Ds结构在烟草中是否表现出相似的特性。建立了一种遗传测定法，以测试双Ds及相关结构在转基因烟草中导致连锁标记基因链霉素磷酸转移酶和β-葡萄糖醛酸酶丢失的能力。如对玉米所描述的那样，一个工程化的双Ds元件和一个简单的Ds元件分别表现出与状态I和状态II Ds元件一致的行为。DNA结构重排伴随着标记基因的丢失。对双Ds结构的剖析表明，直接定向的Ds的左端和右端足以导致所观察到的不稳定性。这一结果表明，直接定向的Ds的左端和右端可参与异常转座事件，这与先前提出的双Ds诱导染色体断裂的两种不同模型一致。两种模型均预测，异常转座事件伴随着半个Ds元件的倒位。仅当基因组中存在激活子活性时，才通过聚合酶链反应实验在烟草和玉米中检测到这种倒位。
