The ability of Papaya ringspot virusstrains overcoming the transgenic resistance of papaya conferred by the coat protein gene is not correlated with higher degrees of sequence divergence from the transgene
The ability of Papaya ringspot virusstrains overcoming the transgenic resistance of papaya conferred by the coat protein gene is not correlated with higher degrees of sequence divergence from the transgene
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DOI：
10.1007/s10658-004-0607-8
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发表时间：
2004-11
影响因子：
1.8
通讯作者：
S. Tripathi;H. Bau;Li-fang Chen;S. Yeh
中科院分区：
文献类型：
--
作者：
S. Tripathi;H. Bau;Li-fang Chen;S. Yeh
发现外壳蛋白（CP）基因介导的转基因抗性是保护木瓜植物免受环斑病毒（PRSV）破坏性病害的最佳途径。为了研究PRSV的变异及其对CP转基因抗性的潜在威胁，本研究从台湾PRSV YK典型花叶株系16-0-1转基因植株中收集了5株病毒，并从台湾不同地区未转化的番木瓜植株中收集了14株病毒。生物学、血清学和分子鉴定结果表明，所有分离株均与PRSV YK有关。其中，转基因番木瓜5—19分离株和未转化番木瓜CS和TD2分离株均能克服番木瓜18—2—4、17—0—5和16—0—1的YK CP基因介导抗性，对夏威夷（HA）、墨西哥（MX）和泰国（TH）不同地理位置的PRSV株系具有较高的抗性。这三个分离株也能在未转化的番木瓜植株上引起比YK诱导的更严重的症状。除宿主反应外，还通过异源双工迁移率测定（HMA）和序列分析分析了19株分离株的变异，并与YK和其他地理菌株进行了比较。HMA分析结果表明，与YK相比，分离株5—19和TD2的CP基因差异较大。然而，对5-19、CS和TD2的序列分析表明，它们的CP编码区和3′非翻译区（utr）与YK的核苷酸同源性分别为93.9 ~ 96.6%和94.2 ~ 97.9%；而HA、MX和TH不能克服转基因抗性的其他地理品系与YK的核苷酸同源性分别为89.8 ~ 92.6%和92.3 ~ 95.3%。我们的研究结果表明，克服转基因抗性的能力并不仅仅与转基因的序列差异程度高有关。讨论了这些PRSV株系克服转基因抗性的可能机制，以及它们对携带PRSV YK CP基因的转基因木瓜株系应用的潜在威胁。
The coat protein (CP) gene mediated transgenic resistance is found to be the best approach for protecting papaya plants against the destructive disease caused byPapaya ringspot viruses(PRSV). In order to study the variability of PRSV and the potential threat to the CP-transgenic resistance, five virus isolates were collected from transgenic plants of papaya line 16-0-1, which carry the CP gene of the typical mosaic strain of Taiwan PRSV YK, in an approved test field and fourteen from untransformed papaya plants in different areas of Taiwan. The results of biological, serological, and molecular characterization indicated that all isolates are related to PRSV YK. Among them, the isolate 5--19 from the transgenic line and the isolates CS and TD2 from untransformed papaya were able to overcome the YK CP gene-mediated resistance of papaya lines 18--2--4, 17-0-5, and 16-0-1, which provide high degrees of resistance to different geographic PRSV strains of Hawaii (HA), Mexico (MX), and Thailand (TH). These three isolates were also able to cause symptoms on untransformed papaya plants more severe than those induced by YK. In addition to the host reactions, the variability of the collected 19 isolates was also analyzed and compared with YK and other geographic strains by heteroduplex mobility assay (HMA) and sequence analyses. The results of HMA indicated that the CP genes of isolates 5--19 and TD2 are more divergent than those of other isolates when compared with YK. However, sequence analyses of the transgenic-resistance overcoming isolates 5-19, CS, and TD2 revealed that their CP coding regions and the 3′ untranslated regions (UTRs) share nucleotide identities of 93.9–96.6% and 94.2–97.9% with those of YK, respectively; whereas the other geographic strains of HA, MX, and TH that could not overcome the transgenic resistance share lower nucleotide identities of 89.8–92.6% and 92.3–95.3% with those of YK, respectively. Our results indicate that the ability for overcoming the transgenic resistance is not solely correlated with higher degrees of sequence divergence from the transgene. The possible mechanism for overcoming the transgenic resistance and the potential threat of these PRSV strains to the application of the transgenic papaya lines carrying PRSV YK CP gene are discussed.