Raizada M N, Brewer K V, Walbot V
Department of Biological Sciences, Stanford University, CA 94305-5020, USA.
Mol Genet Genomics. 2001 Mar;265(1):82-94. doi: 10.1007/s004380000393.
Transgenic maize expressing luciferase under the control of the mudrB terminal inverted repeat promoter (TIRB) of the MuDR transposon was assayed for transgene expression in active and inactive Mutator lines. We find that active MuDR elements increase TIRB-luciferase expression by 2- to 10-fold, relative to nonMuDR or silenced MuDR lines, in embryonic leaves in 75% of plants tested. However, this increase does not persist in juvenile and adult leaves. In pollen, TIRB-luciferase expression is up to 100-fold higher than in leaves but is unaffected by the presence or absence of active MuDR. Because the MuRA transposase binds to a motif within TIRB, we hypothesize that MURA may act as a weak transcriptional activator of TIRB or may partly inhibit host-induced silencing of TIRB in active Mutator lines during the early stages of somatic growth. Our results contrast with those for the maize transposon Spm, in which the TNPA transposase acts as a repressor of the Spm promoter in active Spm lines.
对在MuDR转座子的mudrB末端反向重复启动子（TIRB）控制下表达荧光素酶的转基因玉米，在活跃和非活跃Mutator系中检测其转基因表达情况。我们发现，相对于非MuDR或沉默的MuDR系，在75%被检测的植株的胚性叶中，活跃的MuDR元件可使TIRB - 荧光素酶表达增加2至10倍。然而，这种增加在幼叶和成熟叶中并不持续。在花粉中，TIRB - 荧光素酶表达比在叶中高至100倍，但不受活跃MuDR存在与否的影响。由于MuRA转座酶与TIRB内的一个基序结合，我们推测MURA可能作为TIRB的弱转录激活因子起作用，或者在体细胞生长早期阶段，在活跃的Mutator系中可能部分抑制宿主诱导的TIRB沉默。我们的结果与玉米转座子Spm的结果形成对比，在活跃的Spm系中，TNPA转座酶作为Spm启动子的抑制因子起作用。
