土传小麦花叶病毒基因组结构和RNA2自发缺失的研究

Genome organizations of soil borne wheat mosaic virus and analysis of spontaneous deletion mutants of its RNA2:

描述了土传小麦花叶病毒 (soil bornewheatmosaicvirus,SBWMV)的基因组结构 ,并将之与一些植物病毒作比较。发现重复摩擦接种或在高温下 (2 5～ 30℃ )培养引起SBWMV部分RNA2序列迅速缺失。在最初几次重复摩擦接种后 ,小麦病株存在野生型SBWMVRNA2和几个不同大小的外壳蛋白通读 (CP RT)基因的缺失突变体。在以后的几次重复摩擦接种后 ,一个缺失突变体成为占优势的形式。这个自发的稳定突变体在RNA2第 14 2 0～ 2 180碱基间发生缺失 ,引起CP RT基因上759个碱基 (2 53个氨基酸 )的缺失 ,且接种到健康小麦幼苗上能引起更为严重的症状。在最初几次接种后出现的较小的缺失并不是较大的缺失发生过程的中间产物。禾谷多粘菌 (Polymyxagrami nis)仅传播野生型SBWMV ,而不传播缺失突变体。SBWMVRNA2缺失突变体在植物叶。

Genome organizations of soil borne wheat mosaic virus (SBWMV) were described and compared to some plant viruses.Repeated mechanical passaging of soil borne wheat mosaic furovirus (SBWMV) or growth at high temperature (25-30℃) results in rapid deletion of part of RNA2.During early passages,plants contain a mixed population of deletion mutants which are located in the coat protein readthrough (CP RT) gene.In later passages,one deletion mutant became dominant.This stable mutant was deleted between nts 1420 and 2180,resulting in the loss of 759 nts (253 amino acids) from the CP RT gene.Smaller deletion in earlier passages are not intermediates in the larger deletion process.Only full length SBWMV RNA2 is transmitted to wheat roots by the viruliferous fungal vector, Polymyxa graminis from field soil and there is no intraplant barrier to the movement of deleted forms of RNA2 between roots and leaves.The spontaneous stable deletion mutant is associated with increased symptom severity further mechanical inoculation to young healthy plants.