Peiró Ana, Cañizares M Carmen, Rubio Luis, López Carmelo, Moriones Enrique, Aramburu José, Sánchez-Navarro Jesús
Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, 46022, Valencia, Spain.
Mol Plant Pathol. 2014 Oct;15(8):802-13. doi: 10.1111/mpp.12142. Epub 2014 May 26.
The avirulence determinant triggering the resistance conferred by the tomato gene Sw-5 against Tomato spotted wilt virus (TSWV) is still unresolved. Sequence comparison showed two substitutions (C118Y and T120N) in the movement protein NSm present only in TSWV resistance-breaking (RB) isolates. In this work, transient expression of NSm of three TSWV isolates [RB1 (T120N), RB2 (C118Y) and non-resistance-breaking (NRB)] in Nicotiana benthamiana expressing Sw-5 showed a hypersensitive response (HR) only with NRB. Exchange of the movement protein of Alfalfa mosaic virus (AMV) with NSm supported cell-to-cell and systemic transport of the chimeric AMV RNAs into N. tabacum with or without Sw-5, except for the constructs with NBR when Sw-5 was expressed, although RB2 showed reduced cell-to-cell transport. Mutational analysis revealed that N120 was sufficient to avoid the HR, but the substitution V130I was required for systemic transport. Finally, co-inoculation of RB and NRB AMV chimeric constructs showed different prevalence of RB or NBR depending on the presence or absence of Sw-5. These results indicate that NSm is the avirulence determinant for Sw-5 resistance, and mutations C118Y and T120N are responsible for resistance breakdown and have a fitness penalty in the context of the heterologous AMV system.
引发番茄基因Sw-5对番茄斑萎病毒（TSWV）产生抗性的无毒决定因子仍未明确。序列比较显示，仅在TSWV抗性突破（RB）分离株的运动蛋白NSm中存在两个替换位点（C118Y和T120N）。在本研究中，在表达Sw-5的本氏烟草中瞬时表达三种TSWV分离株[RB1（T120N）、RB2（C118Y）和非抗性突破（NRB）]的NSm，结果显示只有NRB能引发过敏反应（HR）。用NSm替换苜蓿花叶病毒（AMV）的运动蛋白，支持嵌合AMV RNA在有或没有Sw-5的情况下在细胞间和系统内转运至烟草中，但在表达Sw-5时，含有NBR的构建体除外，不过RB2的细胞间转运有所减少。突变分析表明，N120足以避免HR，但V130I替换对于系统转运是必需的。最后，RB和NRB AMV嵌合构建体的共接种显示，根据Sw-5的存在与否，RB或NBR的流行情况不同。这些结果表明，NSm是Sw-5抗性的无毒决定因子，C118Y和T120N突变是抗性丧失的原因，并且在异源AMV系统中对适应性有不利影响。
