Loss and gain of elicitor function of Soybean mosaic virus G7 provoking Rsv1-mediated lethal systemic hypersensitive response maps to P3
Loss and gain of elicitor function of Soybean mosaic virus G7 provoking Rsv1-mediated lethal systemic hypersensitive response maps to P3
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DOI：
10.1128/jvi.79.2.1215-1222.2005
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发表时间：
2005-01-01
影响因子：
5.4
通讯作者：
Hill, JH
中科院分区：
文献类型：
--
作者：
Hajimorad, MR;Eggenberger, AL;Hill, JH
Rsv1 是大豆 PI 96983 (Rsv1) 中的单一显性抗性基因，对所有已知的美国大豆花叶病毒 (SW) 株（G7 和 G7d 除外）具有极强的抗性。 SMV-G7 会引发致命的全身过敏反应 (LSHR)，而 SMV-G7d（SMV-G7 的实验进化变体）会诱导全身嵌合。为了鉴定 Rsv1 介导的 LSHR 的激发子，通过在分子克隆的 SMV-G7 (pSMV-G7) 和 SMV-G7d (pSMV-G7d) 之间交换片段构建嵌合体，并在 PI 96983 (Rsv1) 上评估它们的激发子功能。仅含有 SMV-G7d 的 P3 的 pSMV-G7 衍生嵌合体失去了引发子功能，而 pSMV-G7d 的相反嵌合体则获得了该功能。两种病毒的 P3 区有 6 个核苷酸不同，其中两个是翻译沉默的。四个氨基酸差异位于前体多肽的第823、915、953和1112位。对两种病毒的定点点突变体的分析表明，导致翻译沉默突变的核苷酸取代以及第 915 位的氨基酸相互取代不会影响引发子功能的丧失或获得。 pSMV-G7 衍生的突变体在其他三个位置中的任何一个处发生氨基酸取代，失去了激发 LSHR 的能力，但反而诱导了 SHR。第 823 位（V 至 M）和第 953 位（K 至 E）处的两个伴随氨基酸取代废除了 pSMV-G7 引发子功能，引发 Rsv1 介导的 SHR。相反，pSMV-G7d 通过在位置 823（M 到 V）处的单个氨基酸取代获得了 Rsv1 介导的 LSHR 的引发子功能，并且在位置 953 或 1112 处具有氨基酸取代的突变体诱导 SHR 而不是嵌合。综上所述，数据表明 SMV 菌株特异性 P3 是 Rsv1 介导的 LSHR 的激发子。
Rsv1, a single dominant resistance gene in soybean PI 96983 (Rsv1), confers extreme resistance against all known American strains of Soybean mosaic virus (SW), except G7 and G7d. SMV-G7 provokes a lethal systemic hypersensitive response (LSHR), whereas SMV-G7d, an experimentally evolved variant of SMV-G7, induces systemic mosaic. To identify the elicitor of Rsv1-mediated LSHR, chimeras were constructed by exchanging fragments between the molecularly cloned SMV-G7 (pSMV-G7) and SMV-G7d (pSMV-G7d), and their elicitor functions were assessed on PI 96983 (Rsv1). pSMV-G7-derived chimeras containing only P3 of SMV-G7d lost the elicitor function, while the reciprocal chimera of pSMV-G7d gained the function. The P3 regions of the two viruses differ by six nucleotides, of which two are translationally silent. The four amino acid differences are located at positions 823, 915, 953, and 1112 of the precursor polypeptide. Analyses of the site-directed point mutants of both the viruses revealed that nucleotide substitutions leading to translationally silent mutations as well as reciprocal amino acid substitution at position 915 did not influence the loss or gain of the elicitor function. pSMV-G7-derived mutants with amino acid substitutions at any of the other three positions lost the ability to provoke LSHR but induced SHR instead. Two concomitant amino acid substitutions at positions 823 (V to M) and 953 (K to E) abolished pSMV-G7 elicitor function, provoking Rsv1-mediated SHR. Conversely, pSMV-G7d gained the elicitor function of Rsv1-mediated LSHR by a single amino acid substitution at position 823 (M to V), and mutants with amino acid substitutions at position 953 or 1112 induced SHR instead of mosaic. Taken together, the data suggest that strain-specific P3 of SMV is the elicitor of Rsv1-mediated LSHR.