SUPPRESSION OF BETA-1,3-GLUCANASE TRANSGENE EXPRESSION IN HOMOZYGOUS PLANTS
SUPPRESSION OF BETA-1,3-GLUCANASE TRANSGENE EXPRESSION IN HOMOZYGOUS PLANTS
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DOI：
10.1002/j.1460-2075.1992.tb05324.x
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发表时间：
1992-07-01
期刊：
影响因子：
11.4
通讯作者：
CASTRESANA, C
中科院分区：
文献类型：
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作者：
DECARVALHO, F;GHEYSEN, G;CASTRESANA, C
将含有烟草plumbaginifolia β-1，3-葡聚糖酶gn 1基因的嵌合构建体引入烟草SR 1中以组成性地产生高水平的酶。我们确定GN 1蛋白代表一种碱性β-1，3-葡聚糖酶同种型，其积累到转基因植物的液泡中。对具有最高水平gn 1表达的转基因植物的后代的分析揭示了一种意想不到的基因抑制现象。植物半合子的T-DNA基因座含有高水平的gn 1 mRNA，并表现出比未转化的植物高14倍的β-1，3-葡聚糖酶活性。然而，gn 1的表达在纯合植物中被完全抑制：没有相应的mRNA或蛋白质可以检测到。这种抑制机制发生在转录后水平，并在发育控制下。此外，通过产生单倍体植物，我们发现这种沉默现象不依赖于同源染色体的相同基因座处存在的T-DNA拷贝之间的等位基因相互作用，而是与植物基因组中的转基因剂量相关。我们推测，相对于其他未知植物产物的水平，高剂量的GN 1蛋白可以触发抑制GN 1表达的细胞过程。
A chimeric construct containing the Nicotiana plumbaginifolia beta-1,3-glucanase gn1 gene was introduced into Nicotiana tabacum SR1 to produce high levels of the enzyme constitutively. We determined that the GN1 protein represents a basic beta-1,3-glucanase isoform which accumulates into the vacuoles of the transgenic plants. Analysis of the progeny of the transgenic plant with the highest levels of gn1 expression revealed an unexpected phenomenon of gene suppression. Plants hemizygous for the T-DNA locus contained high levels of gn1 mRNA and exhibited a 14-fold higher beta-1,3-glucanase activity than untransformed plants. However, the expression of gn1 was completely suppressed in the homozygous plants: no corresponding mRNA or protein could be detected. This suppression mechanism occurs at a post-transcriptional level and is under developmental control. In addition, by generating haploid plants we found that this silencing phenomenon is not dependent on allelic interaction between T-DNA copies present at the same locus of homologous chromosomes, but rather is correlated with the transgene dose in the plant genome. We postulate that high doses of GN1 protein relative to the level(s) of other still unknown plant products could trigger the cellular processes directed to suppress gn1 expression.