Meshi T, Motoyoshi F, Maeda T, Yoshiwoka S, Watanabe H, Okada Y
Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
Plant Cell. 1989 May;1(5):515-22. doi: 10.1105/tpc.1.5.515.
A resistance-breaking strain of tobacco mosaic virus (TMV), Ltb1, is able to multiply in tomatoes with the Tm-2 gene, unlike its parent strain, L. Nucleotide sequence analysis of Ltb1 RNA revealed two amino acid changes in the 30-kD protein: from Cys68 to Phe and from Glu133 to Lys (from L to Ltb1). Strains with these two changes generated in vitro multiplied in tomatoes with the Tm-2 gene and induced essentially the same symptoms as those caused by Ltb1. Strains with either one of the two changes did not overcome the resistance as efficiently as Ltb1, although increased levels of multiplication were observed compared with the L strain. Results showed that both mutations are involved in the resistance-breaking property of Ltb1. Sequence analysis indicated that another resistance-breaking strain and its parent strain had two amino acid changes in the 30-kD protein: from Glu52 to Lys and from Glu133 to Lys. The fact that the amino acid changes occurred in or near the well conserved regions in the 30-kD protein suggests that the mechanism of Tm-2 resistance may be closely related to the fundamental function of the 30-kD protein, presumably in cell-to-cell movement.
一种能打破抗性的烟草花叶病毒（TMV）毒株Ltb1，与其亲本毒株L不同，它能够在携带Tm - 2基因的番茄中繁殖。对Ltb1 RNA的核苷酸序列分析显示，其30-kD蛋白中有两个氨基酸发生了变化：从Cys68变为Phe，从Glu133变为Lys（从L变为Ltb1）。体外产生的具有这两种变化的毒株能在携带Tm - 2基因的番茄中繁殖，并引发与Ltb1引发的症状基本相同的症状。具有这两种变化之一的毒株虽然与L毒株相比繁殖水平有所提高，但并不能像Ltb1那样有效地克服抗性。结果表明，这两种突变都与Ltb1打破抗性的特性有关。序列分析表明，另一种打破抗性的毒株及其亲本毒株在30-kD蛋白中有两个氨基酸变化：从Glu52变为Lys，从Glu133变为Lys。氨基酸变化发生在30-kD蛋白中保守区域内或附近这一事实表明，Tm - 2抗性机制可能与30-kD蛋白的基本功能密切相关，推测是在细胞间移动方面。
