Rapid generation of genetic heterogeneity in progenies from individual cDNA clones of peach latent mosaic viroid in its natural host
Rapid generation of genetic heterogeneity in progenies from individual cDNA clones of peach latent mosaic viroid in its natural host
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DOI：
10.1099/0022-1317-80-8-2239
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发表时间：
1999-08-01
影响因子：
3.8
通讯作者：
Flores, R
中科院分区：
文献类型：
--
作者：
Ambrós, S;Hernández, C;Flores, R
类病毒是具有自主复制能力的小单链环状RNA，是对完整RNA基因组进行进化研究的独特系统。测定了桃潜伏花叶类病毒(PLMVd)的36个后代变异株的一级结构，这些变异株是由桃指示剂GF-305与4个致病力不同的PLMVd cDNA进化而来的。大多数后代变异株都有独特的序列，这表明PLMVd天然分离物的极端异质性很可能是由于这种RNA积累变化的内在能力造成的，而不是在田间条件下重复接种相同的单株树木。来自单个PLMVd序列的群体结构因观察到的表型而不同。突变体GDS6诱导了可重复的症状侵染，并产生了更一致的后代，保留了一些亲本特征，而诱导表型可变的突变体GDS15表现出更复杂的行为，在有症状和无症状的个体上产生了两个不同的后代。从引发潜伏感染的变体esc10和is11衍生的后代遵循类似的进化模式，导致了由两组主要变体组成的种群结构，其中一组由与亲本序列密切相关的变体形成。PLMVd的进化速度明显高于报道的马铃薯纺锤型块茎类病毒，这可能是导致PLMVd严重自然分离物症状波动的原因之一。然而，在PLMVd后代中观察到的多态确实保留了先前为这种类病毒提出的一些结构和功能元件，支持它们作为限制从头产生的PLMVd准种的遗传分歧的事实。
Viroids, small single-stranded circular RNAs endowed with autonomous replication, are unique systems to conduct evolutionary studies of complete RNA genomes. The primary structure of 36 progeny variants of peach latent mosaic viroid (PLMVd), evolved from inoculations of the peach indicator GF-305 with four individual PLMVd cDNAs differing in their pathogenicity, has been determined. Most progeny variants had unique sequences, revealing that the extremely heterogeneous character of PLMVd natural isolates most probably results from the intrinsic ability of this RNA to accumulate changes, rather than from repeated inoculations of the same individual trees under field conditions. The structure of the populations derived from single PLMVd sequences differed according to the observed phenotype. Variant gds6 induced a reproducible symptomatic infection and gave rise to a more uniform progeny that preserves some parental features, whereas variant gds15, which induced a variable phenotype, showed a more complex behaviour, generating two distinct progenies in symptomatic and asymptomatic individual plants. Progenies derived from variants esc10 and Is11,which incited latent infections, followed a similar evolutionary pattern, leading to a population structure consisting of two main groups of variants, one of which was formed by variants closely related to the parental sequence. The evolution rate exhibited by PLMVd, considerably higher than that reported for potato spindle tuber viroid, may contribute to the fluctuating symptomatology of the severe PLMVd natural isolates. However, the polymorphism observed in PLMVd progenies does preserve some structural and functional elements previously proposed for this viroid, supporting the fact that they act as constraints limiting the genetic divergence of PLMVd quasispecies generated de novo.