Three genes of Citrus tristeza virus are dispensable for infection and movement throughout some varieties of citrus trees.
Three genes of Citrus tristeza virus are dispensable for infection and movement throughout some varieties of citrus trees.
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DOI：
10.1016/j.virol.2007.12.038
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发表时间：
2008-07
期刊：
影响因子：
3.7
通讯作者：
S. Tatineni;C. Robertson;S. Garnsey;M. Bar-joseph;S. Gowda;W. Dawson
中科院分区：
文献类型：
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作者：
S. Tatineni;C. Robertson;S. Garnsey;M. Bar-joseph;S. Gowda;W. Dawson
柑橘衰退病毒（Citrus tristeza virus，CTV）是梭状病毒科（Closteroviridae）的一种病毒，其基因组由12个开放阅读框（Open Reading Frame，ORFs）组成，全长19.3kb。CTV基因组包含两组保守基因，这是该病毒组的特征，复制基因块（ORF 1a和1b）和五重基因块（p6、HSP 70 h、p61、CPm和CP）。除p6基因外，它们是复制和病毒体组装所必需的。CTV在基因组的3′端含有5个额外的基因，p33，p18，p13，p20和p23，其中一些（p33，p18和p13）在该病毒组的其他成员中并不保守，并且已经被认为已经进化为与柑橘宿主特异性相互作用。本研究对p33、p6、p18、p13和p20等5个菌株系统侵染柑桔的条件进行了研究。在p6或p20 ORF缺失的病毒突变体未能感染柑橘植物系统，这表明它们可能在病毒易位/系统感染中的作用。然而，我们发现p33，p18或p13 ORF内的缺失单独导致病毒感染，繁殖和传播整个柑橘树的能力没有显着损失。此外，在所有可能的组合中的p33、p18和p13基因中的缺失（包括所有三个基因中的缺失）允许病毒系统性地侵入柑橘树。绿色荧光蛋白标记的CTV变体在p33 ORF或p33、p18和p13 ORF中具有缺失，证明这些缺失突变体的运动和分布与野生型病毒的运动和分布相似。
Citrus tristeza virus (CTV), a member of the Closteroviridae, possesses a 19.3-kb positive-stranded RNA genome that is organized into twelve open reading frames (ORFs). The CTV genome contains two sets of conserved genes, which are characteristic of this virus group, the replication gene block (ORF 1a and 1b) and the quintuple gene block (p6, HSP70 h, p61, CPm, and CP). With the exception of the p6 gene, they are required for replication and virion assembly. CTV contains five additional genes, p33, p18, p13, p20 and p23, in the 3′ half of the genome, some of which (p33, p18 and p13) are not conserved among other members of this virus group, and have been proposed to have evolved for specific interactions with the citrus host. In the present study, the requirements for systemic infection of citrus trees of p33, p6, p18, p13 and p20 were examined. Viral mutants with a deletion in the p6 or the p20 ORF failed to infect citrus plants systemically, suggesting their possible roles in virus translocation/systemic infection. However, we found that deletions within the p33, p18 or p13 ORF individually resulted in no significant loss of ability of the virus to infect, multiply, and spread throughout citrus trees. Furthermore, deletions in the p33, p18 and p13 genes in all possible combinations including deletions in all three genes allowed the virus to systemically invade citrus trees. Green fluorescent protein-tagged CTV variants with deletions in the p33 ORF or the p33, p18 and p13 ORFs demonstrated that the movement and distribution of these deletion mutants were similar to that of the wild-type virus.