Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan.
EMBO J. 1988 Jun;7(6):1575-81. doi: 10.1002/j.1460-2075.1988.tb02982.x.
A resistance-breaking strain of tobacco mosaic virus (TMV), Ltal, is able to multiply in tomatoes with the Tm-1 gene, unlike its parent strain, L. Comparison of the genomic sequences of L and Lta1 revealed two base substitutions resulting in amino acid changes in the 130 and 180 kd proteins: Gln-979 --> Glu and His-984 --> Tyr. To clarify their involvement in the resistance-breaking property of Lta1, the two substitions were introduced into L by an in vitro transcription system to generate a mutant strain, T1. T1 multiplied in Tm-1/Tm-1 tomatoes with symptoms as did Lta1. Two additional mutant strains were constructed, each of which had one base substitution which caused a His-984 --> Tyr change (T2) or a Gln-979 --> Glu change (T3). T3 multiplied in tomato plants and protoplasts with the Tm-1 gene, indicating that the single base substitution is sufficient to overcome the resistance. T2 also multiplied, but its multiplication was greatly decreased. Although no sequence changes were detected in any progeny viruses recovered from plants without the Tm-1 gene, progeny viruses recovered from T2- or T3- inoculated Tm-1/Tm-1 tomatoes contained in most cases viruses with additional second base substitutions. They caused amino acid changes near the mutagenized residues, suggesting that the ability of T3 to overcome the resistance is not the same as that of Lta1. Sequencing of the genomic RNAs of other independently isolated resistance-breaking strains revealed the same two base substitutions found in the Lta1 RNA. These observations suggest that the two concomitant base substitutions, and possibly also the resulting amino acid changes, guarantee successful replication of these TMV strains in tomatoes containing the Tm-1 gene. A strong correlation was found between the ability to overcome the resistance and a decrease in local net charge, suggesting the involvement of an electrostatic interaction between the viral 130 and 180 kd proteins and a putative host resistance factor.
一个抗药性的烟草花叶病毒（TMV）株系，Lta1，与亲本株系 L 不同，能够在含有 Tm-1 基因的番茄中繁殖。比较 L 和 Lta1 的基因组序列，发现两个碱基的取代导致 130 和 180kd 蛋白的氨基酸变化：Gln-979 --> Glu 和 His-984 --> Tyr。为了阐明这两个取代在 Lta1 的抗药性中的作用，通过体外转录系统将这两个取代引入 L 中，产生一个突变株系 T1。T1 在 Tm-1/Tm-1 番茄中繁殖，并表现出与 Lta1 相同的症状。构建了另外两个突变株系，每个株系都有一个碱基取代，导致 His-984 --> Tyr 变化（T2）或 Gln-979 --> Glu 变化（T3）。T3 在含有 Tm-1 基因的番茄植株和原生质体中繁殖，表明单个碱基取代足以克服抗性。T2 也繁殖了，但繁殖能力大大降低。尽管在没有 Tm-1 基因的植物中回收的子代病毒中没有检测到序列变化，但从 T2 或 T3 接种的 Tm-1/Tm-1 番茄中回收的子代病毒在大多数情况下含有额外的第二个碱基取代的病毒。它们导致突变残基附近的氨基酸变化，表明 T3 克服抗性的能力与 Lta1 不同。对其他独立分离的抗药性株系基因组 RNA 的测序揭示了与 Lta1 RNA 相同的两个碱基取代。这些观察结果表明，这两个同时发生的碱基取代，以及可能还有由此产生的氨基酸变化，保证了这些 TMV 株系在含有 Tm-1 基因的番茄中的成功复制。发现能够克服抗性的能力与局部净电荷的降低之间存在很强的相关性，这表明病毒 130 和 180kd 蛋白与一个假定的宿主抗性因子之间存在静电相互作用。
Zotero 插件
