Hobbs S L, Kpodar P, DeLong C M
Plant Biotechnology Institute, National Research Council of Canada, Saskatoon, Saskatchewan.
Plant Mol Biol. 1990 Dec;15(6):851-64. doi: 10.1007/BF00039425.
Inter-transformant variability in the expression of introduced genes was studied in the R1 and R2 generations of 10 tobacco transformants, produced by Agrobacterium-mediated transformation. In replicated and physiologically equivalent material, tranformants showed considerable variability in the expression of the reporter gene uidA as shown by transcript levels and beta-glucuronidase (GUS) activity. However, homozygous R2 material could be investigated for seven of the transformants and among these, and in one line in which two inserts could segregate independently, this inter-transformant variability was reduced to simple bimodal expression. The two levels of expression for GUS activity in leaves were high or low (approximately 2.5 or 0.3 nmol cm-2 min-1 respectively), with no continuous variation. Transformants in the high group had single T-DNA insertions, while those in the low group had multiple T-DNA insertions, at the same or different loci. Within each group, although T-DNA was apparently integrated at different sites in the plant genome, there was no evidence of position effects. GUS activity levels of the transformants were very similar in the field and in environmentally controlled conditions under high or low light. Plants with multiple insertions and low expression also tended to have increased methylation of the integrated T-DNA.
在通过农杆菌介导转化产生的10个烟草转化体的R1和R2代中，研究了导入基因表达的转化体间变异性。在重复且生理等效的材料中，转化体在报告基因uidA的表达上表现出相当大的变异性，转录水平和β-葡萄糖醛酸酶（GUS）活性显示了这一点。然而，对于其中7个转化体的纯合R2材料可以进行研究，在这些材料中，以及在一个两个插入片段可以独立分离的株系中，这种转化体间变异性降低为简单的双峰表达。叶片中GUS活性的两个表达水平分别为高或低（分别约为2.5或0.3 nmol cm-2 min-1），没有连续变化。高表达组的转化体具有单个T-DNA插入，而低表达组的转化体在相同或不同位点具有多个T-DNA插入。在每组中，尽管T-DNA显然整合在植物基因组的不同位点，但没有位置效应的证据。在田间以及在高光或低光环境控制条件下，转化体的GUS活性水平非常相似。具有多个插入且表达低的植株中，整合的T-DNA甲基化也往往增加。
