Gal-On A, Kaplan I, Palukaitis P
Department of Plant Pathology, Cornell University, Ithaca, New York 14853, USA.
Virology. 1995 Apr 1;208(1):58-66. doi: 10.1006/viro.1995.1129.
The presence of cucumber mosaic virus (CMV) satellite RNA usually reduces the yield of accumulated helper virus, although more so in solanaceous than in cucurbit hosts. The accumulation of viral RNA and viral-encoded proteins of two strains of CMV (Fny- and Sny-) known to differ in their ability to support satellite RNA in zucchini squash was examined in squash and tobacco to determine the effect of satellite RNA on the accumulation of viral-associated components. In the absence of satellite RNA, Fny- and Sny-CMV showed similar levels of accumulation of RNA at 7 days postinoculation (p.i.), but by 14 days p.i. the Fny-CMV RNAs accumulated to lower levels than did both strains at 7 days p.i., in either host. The levels of accumulated Sny-CMV-encoded proteins were higher than those encoded by Fny-CMV in tobacco, but not squash plants, at 7 days p.i. At 14 days p.i., for Fny-CMV vs Sny-CMV, there were differences in the levels of accumulation of most CMV-encoded proteins in both hosts, more exacerbated in tobacco vs squash. The effect of satellite RNA was to intensify these differences; that is, by 7 days p.i., satellite RNA reduced the accumulation of Fny-CMV RNAs 1 and 2 and their encoded proteins in both tobacco and squash but had little or no effect on the accumulation of Sny-CMV RNAs or encoded proteins. By 14 days p.i., the levels of accumulation of all Fny-CMV RNAs and encoded proteins were severely reduced in both hosts, and the levels of accumulation of Sny-CMV RNAs 1 and 2 and their encoded proteins were also reduced in tobacco, but not squash. Sny-CMV did not support satellite RNA accumulation in squash plants or protoplasts. Satellite RNA did not appear to have a direct effect on the movement of either CMV strain. Rather, accumulation studies in tobacco protoplasts indicated that the difference in response of Fny-CMV vs Sny-CMV to satellite RNA in tobacco was due to the extent to which satellite RNA affected the levels of RNA 1, and to a lesser extent RNA 2, and their encoded proteins, 1a and 2a, both components of the CMV replicase.
黄瓜花叶病毒（CMV）卫星RNA的存在通常会降低辅助病毒的积累产量，不过在茄科植物中比在葫芦科宿主中表现得更为明显。研究了两种已知在西葫芦中支持卫星RNA能力不同的CMV毒株（Fny-和Sny-）的病毒RNA和病毒编码蛋白在西葫芦和烟草中的积累情况，以确定卫星RNA对病毒相关成分积累的影响。在没有卫星RNA的情况下，Fny-CMV和Sny-CMV在接种后7天（p.i.）时RNA积累水平相似，但到接种后14天，在任一宿主中，Fny-CMV RNA的积累水平都低于两种毒株在接种后7天时的水平。在接种后7天，烟草中积累的Sny-CMV编码蛋白水平高于Fny-CMV编码的蛋白水平，但在西葫芦植株中并非如此。在接种后14天，对于Fny-CMV和Sny-CMV而言，两种宿主中大多数CMV编码蛋白的积累水平存在差异，在烟草中比在西葫芦中差异更明显。卫星RNA的作用是加剧这些差异；也就是说，到接种后7天，卫星RNA降低了烟草和西葫芦中Fny-CMV RNA 1和2及其编码蛋白的积累，但对Sny-CMV RNA或编码蛋白的积累几乎没有影响。到接种后14天，两种宿主中所有Fny-CMV RNA和编码蛋白的积累水平都大幅降低，烟草中Sny-CMV RNA 1和2及其编码蛋白的积累水平也降低了，但在西葫芦中未降低。Sny-CMV在西葫芦植株或原生质体中不支持卫星RNA的积累。卫星RNA似乎对两种CMV毒株的移动没有直接影响。相反，在烟草原生质体中的积累研究表明，Fny-CMV和Sny-CMV在烟草中对卫星RNA反应的差异是由于卫星RNA影响RNA 1水平的程度，以及在较小程度上影响RNA 2及其编码蛋白1a和2a（CMV复制酶的两个组分）水平的程度。
