In tomato, infections by tomato mosaic virus are controlled by durable Tm-2(2) resistance. In order to gain insight into the processes underlying disease resistance and its durability, we cloned and analysed the Tm-2(2) resistance gene and the susceptible allele, tm-2. The Tm-2(20 gene was isolated by transposon tagging using a screen in which plants with a destroyed Tm-2(2) gene survive. The Tm-2(2) locus consists of a single gene that encodes an 861 amino acid polypeptide, which belongs to the CC-NBS-LRR class of resistance proteins. The putative tm-2 allele was cloned from susceptible tomato lines via PCR with primers based on the Tm-2(2) sequence. Interestingly, the tm-2 gene has an open reading frame that is comparable to the Tm-2(2) allele. Between the tm-2 and the Tm-2(2) polypeptide 38 amino acid differences are present of which 26 are located in the second half of the LRR-domain. Susceptible tomato plants, which were transformed with the Tm-2(2) gene, displayed resistance against ToMV infection. In addition, virus specificity, displayed by the Tm-2(2) resistance was conserved in these transgenic lines. To explain the durability of this resistance, it is proposed that the Tm-2(2)-encoded resistance is aimed at the Achilles' heel of the virus.

中文翻译：

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番茄Lycopersicon esculentum的番茄抗番茄花叶病毒抗性基因Tm-2（2）的克隆与鉴定。

在番茄中，番茄花叶病毒的感染受持久的Tm-2（2）耐药性控制。为了深入了解抗病性及其持久性的过程，我们克隆并分析了Tm-2（2）抗性基因和易感等位基因tm-2。Tm-2（20）基因是通过转座子标签筛选的，其中Tm-2（2）基因被破坏的植物在其中存活下来，而Tm-2（2）基因座由一个编码861个氨基酸多肽的单一基因组成，属于抗性蛋白CC-NBS-LRR类，通过基于Tm-2（2）序列的引物通过PCR从易感番茄品系中克隆了推定的tm-2等位基因，有趣的是，tm-2基因具有一个与Tm-2（2）等位基因相当的开放阅读框。在tm-2和Tm-2（2）多肽之间存在38个氨基酸差异，其中26个位于LRR结构域的后半部分。用Tm-2（2）基因转化的易感番茄植株显示出对ToMV感染的抵抗力。另外，在这些转基因株系中保守了由Tm-2（2）抗性显示的病毒特异性。为了解释这种抗药性的持久性，建议将Tm-2（2）编码的抗药针对该病毒的致命弱点。