Célix A, Burgyán J, Rodríguez-Cerezo E
Centro Nacional de Biotecnología (CSIC), Cantoblanco, Madrid, 28049, Spain.
Virology. 1999 Sep 15;262(1):129-38. doi: 10.1006/viro.1999.9865.
The biological properties of two recently described satellite RNAs of tomato bushy stunt virus (TBSV) were analyzed in natural and experimental hosts. Full-length cDNA clones were constructed for sat RNAs B1(822 nt) and B10 (612 nt) and used in inoculations with satellite-free transcripts of different tombusviruses. In all virus-host combinations tested, TBSV sat RNA B10 drastically reduced the accumulation of viral genomic RNA and attenuated symptoms. In contrast, sat RNA B1 caused a less marked reduction of viral RNA level and did not have any effect on symptoms. Experiments with Nicotiana benthamiana protoplasts showed that the differential effects of sat RNAs B1 and B10 on TBSV titer were related to differential abilities to interfere with virus replication. Three tombusviruses tested were able to maintain both sat RNAs in N. benthamiana plants, although carnation Italian ringspot virus (CIRV) was a poor helper for sat RNA B1. Using chimeric viruses, a strong determinant for low sat RNA B1 accumulation was mapped to the 5'-terminal part of the genome of CIRV. The poor helper activity of CIRV was shown to be due to low sat RNA B1 replication. A single-nucleotide mutation in the start codon of CIRV ORF1 restored the ability to replicate sat RNA B1 to high levels. This mutant encodes an ORF1 that is 22 amino acids shorter at the N-terminus than the wild-type virus.
对番茄丛矮病毒（TBSV）最近描述的两种卫星RNA的生物学特性在天然宿主和实验宿主中进行了分析。构建了卫星RNA B1（822个核苷酸）和B10（612个核苷酸）的全长cDNA克隆，并用于接种不同番茄病毒属病毒的无卫星转录本。在所有测试的病毒-宿主组合中，TBSV卫星RNA B10显著降低了病毒基因组RNA的积累并减轻了症状。相比之下，卫星RNA B1对病毒RNA水平的降低作用较小，并且对症状没有任何影响。用本氏烟草原生质体进行的实验表明，卫星RNA B1和B10对TBSV滴度的不同影响与干扰病毒复制的不同能力有关。测试的三种番茄病毒属病毒能够在本氏烟草植株中维持这两种卫星RNA，尽管香石竹意大利环斑病毒（CIRV）对卫星RNA B1的辅助作用较差。使用嵌合病毒，将卫星RNA B1低积累的一个强决定因素定位到CIRV基因组的5'-末端部分。结果表明，CIRV辅助活性差是由于卫星RNA B1复制水平低。CIRV ORF1起始密码子中的一个单核苷酸突变恢复了将卫星RNA B1复制到高水平的能力。该突变体编码的ORF1在N端比野生型病毒短22个氨基酸。
