Bhattacharyya M K, Gonzales R A, Kraft M, Buzzell R I
Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, OK 73402, USA.
Plant Mol Biol. 1997 May;34(2):255-64. doi: 10.1023/a:1005851623493.
We have isolated and characterized Tgmr, a copia-like retrotransposon, linked tightly to the Rps1-k allele that confers race-specific resistance of soybean to the the fungal pathogen Phytophthora sojae. Southern analysis followed by PCR and sequence analyses, using primers based on sequences flanking the insertion site confirmed that the element was inserted in the neighboring region of Rps1-k but not in that of the other four Rps1 alleles. This implies that Tgmr was transposed into the Rps1-k flanking site after the divergence of Rps1 alleles. Southern analysis of a series of diverse soybean cultivars revealed a high level of polymorphism of Tgmr-related sequences. These results indicate that this low copy retroelement family could have been active in the soybean genome in the recent past. Tgmr contains long terminal repeats (LTR) and four non-overlapping open reading frames (ORF), presumably originating from mutations leading to stop codons of a single ORF. The conserved domains for gag, protease, integrase, reverse transcriptase and RNaseH are present in the internal portion of the element. However, the protease, reverse transcriptase and RNaseH of this element are non-functional due to the presence of several stop codons. Possible transactivation of Tgmr and application of this element in insertional mutagenesis for soybean are discussed.
我们已经分离并鉴定了Tgmr，一种类copia逆转录转座子，它与Rps1 - k等位基因紧密相连，该等位基因赋予大豆对真菌病原体大豆疫霉的小种特异性抗性。通过Southern分析，随后进行PCR和序列分析，使用基于插入位点侧翼序列的引物，证实该元件插入到Rps1 - k的邻近区域，而不是其他四个Rps1等位基因的邻近区域。这意味着Tgmr在Rps1等位基因分化后转座到Rps1 - k侧翼位点。对一系列不同大豆品种的Southern分析揭示了Tgmr相关序列的高度多态性。这些结果表明，这个低拷贝逆转录元件家族可能在近期大豆基因组中具有活性。Tgmr包含长末端重复序列（LTR）和四个不重叠的开放阅读框（ORF），推测是由单个ORF的终止密码子突变产生的。该元件内部存在gag、蛋白酶、整合酶、逆转录酶和核糖核酸酶H的保守结构域。然而，由于存在几个终止密码子，该元件的蛋白酶、逆转录酶和核糖核酸酶H无功能。讨论了Tgmr可能的反式激活以及该元件在大豆插入诱变中的应用。
