Agranovsky A A
Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia.
Adv Virus Res. 1996;47:119-58. doi: 10.1016/s0065-3527(08)60735-6.
This chapter focuses on the molecular organization, evolution, and expression of closterovirus genomes, as well as on their unique particle structure. The closterovirus group combines several positive-strand RNA viruses with very flexuous filamentous particles, of which beet yellows virus (BYV) is the type virus. Closteroviruses are distinct from other RNA viruses of plants in some important phenomenological aspects. They have genomes of up to 20 kilobases (kb), a value comparable only to those of the animal coronaviruses and toroviruses, which have the largest RNA genomes of all positive-strand RNA viruses. The existence of such genomes having a coding capacity several times that of an average RNA virus genome raises questions as to the trend whereby the long genomes have evolved and the possible novel functions they have acquired. The dramatic increase in the closterovirus genome coding capacity may be linked to the distinct ecological niche they occupy. Thus, closteroviruses are the only elongated plant viruses known so far to cause phloem-limited infections in plants and to persist in their insect vectors for many hours, in contrast to only minutes.
本章重点关注长线形病毒基因组的分子组织、进化和表达，以及它们独特的粒子结构。长线形病毒组包含几种具有非常柔韧丝状粒子的正链RNA病毒，其中甜菜黄化病毒（BYV）是典型病毒。长线形病毒在一些重要的现象学方面与植物的其他RNA病毒不同。它们拥有长达20千碱基（kb）的基因组，这一数值仅与动物冠状病毒和环曲病毒相当，而动物冠状病毒和环曲病毒在所有正链RNA病毒中拥有最大的RNA基因组。如此具有比普通RNA病毒基因组编码能力高出数倍的基因组的存在，引发了关于长基因组进化趋势以及它们可能获得的新功能的问题。长线形病毒基因组编码能力的显著增加可能与它们所占据的独特生态位有关。因此，与仅持续几分钟相比，长线形病毒是迄今为止已知的唯一一类能在植物中引起韧皮部局限感染并在其昆虫介体中持续存在数小时的细长植物病毒。
