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Abstract：
Tobacco vein necrosis (TVN) is a complex phenomenon regulated by different genetic determinants mapped in the HC-Pro protein (amino acids N330, K391 and E410) and in two regions of potato virus Y (PVY) genome, corresponding to the cytoplasmic inclusion (CI) protein and the nuclear inclusion protein a-protease (NIa-Pro), respectively. A new determinant of TVN was discovered in the MK isolate of PVY which, although carried the HC-Pro determinants associated to TVN, did not induce TVN. The HC-Pro open reading frame (ORF) of the necrotic infectious clone PVY N605 was replaced with that of the non-necrotic MK isolate, which differed only by one amino acid at position 392 (T392 instead of I392). The cDNA clone N605_MKHCPro inoculated in tobacco induced only weak mosaics at the systemic level, demostrating that the amino acid at position 392 is a new determinant for TVN. No significant difference in accumulation in tobacco was observed between N605 and N605_MKHCPro. Since phylogenetic analyses showed that the loss of necrosis in tobacco has occurred several times independently during PVY evolution, these repeated evolutions strongly suggest that tobacco necrosis is a costly trait in PVY.
摘要：
烟草静脉坏死（TVN）是由HC-Pro蛋白（氨基酸N330，K391和E410）和马铃薯病毒Y（PVY）基因组的两个区域中的不同遗传决定子调节的复杂现象。对应于细胞质包涵蛋白（CI）和核包涵蛋白α-蛋白酶（NIa-Pro），分别。在PVY的MK分离株中发现了一个新的TVN决定因素，尽管携带了与TVN相关的HC-Pro决定因素，没有诱导TVN。坏死感染性克隆PVYN605的HC-Pro开放阅读框（ORF）被非坏死MK分离株取代，其仅在位置392处的一个氨基酸(T392代替I392)不同。接种在烟草中的cDNA克隆N605_MKHCPro仅在系统水平上诱导弱马赛克，证明位置392的氨基酸是TVN的新决定因素。在N605和N605_MKHCPro之间没有观察到烟草中积累的显著差异。由于系统发育分析表明，在PVY进化过程中，烟草中坏死的损失已经独立发生了几次，这些反复的演变强烈表明，烟草坏死是PVY的一种昂贵特征。
