Bamboo Mosaic virus and Its Associated Satellite RNA

竹嵌紋病毒及其衛星核酸

林納生(Na-Sheng Lin) ； 徐堯煇(Yau-Heiu Hsu)

《植物病理學會刊》 3卷1期 (1994/03) Pp. 65-71

https://doi.org/10.6649/PPB.199403_3(1).0008

摘要

竹嵌紋病毒(Bamboo mosaic virus, BaMV)嚴重危害台灣12種重要經濟竹種，包括3變種和3栽培種。大部分被感染之竹類都屬於地下莖合軸叢生型(Pachymorph-type rhizomes)，且多屬於麻竹屬(Dendrocalamus)及蓬萊竹屬(Bambusa)。竹嵌紋病毒含有單一正股之RNA基因體約6.4 Kb長。核苷酸序列分析顯示，BaMv之基因體構造和馬鈴薯X病毒群(Potexvirus)之其它病毒類似,共含有五個轉譯區(open reading frames, ORFs)。ORF1位在RNA之5'端,可合成155 KD蛋白,且具RNA複製酶圖式，而鞘蛋白25 KD基因位在RNA之3'端，介於兩者之間有三個基因區(triple gene blocks),可能與病毒之移動有關。在生體外兔子網狀紅血球抽出物轉譯系統(rabbit reticulocyte lysate, RRL)中，BaMV RNA可合成160 KD之大蛋白，但無法合成病毒之鞘蛋白。在感病之細胞中，可偵測到病毒之二段次基因RNA (subgenomic RNA)，長約2.0 kb和1.0 kbo。BaMv有其特殊之細胞病理特徵，它除了在感病細胞內大量累積病毒顆粒外，亦會合成電子密度高之結晶體(electron-dense crystalline bodies, EDCBs)。此結晶體在病毒顆粒出現之前，即在葉綠體出現，因此，可視爲感病之表徵。隨後，病毒在葉綠體之外膜出現，並伴隨大量在細胞質之EDCBs，最後，EDCBs侷限在細胞質或細胞核中。以免疫電子顯微鏡標定病毒鞘蛋白，顯示鞘蛋白並未出現在葉綠體、粒腺體或細胞核等任何胞器中，同時EDCBs與鞘蛋白亦無血清關係，但利用BaMV 3'端之核酸探針行原位雜交觀察，顯示BaMv RNA大量聚集在感病細胞之葉綠體、粒腺體和細胞核中。最近從感病之泰山竹(Bambusa vulgaris)得一分離株，它不僅含有基因組RNA，另含有長約850NT之短RNA。以北方雜配接種試驗和免疫膠金標定，結果顯示，此短RNA爲BaMV之衛星核酸。但此衛星核酸含有合成20KD非構造蛋白之能力，與生體外轉譯結果吻合，這是馬鈴薯X病毒群中首次發現之術星核酸。

關鍵字

馬鈴薯X群病毒 ； 竹嵌紋病毒 ； 衛星核酸

並列摘要

Bamboo mosaic virus (BaMV) infects 12 economic bamboo species, including 3 varieties and 3 cultivars, in Taiwan. Most of the susceptible bamboo species have pachymorph-type rhizomes and belong to the genera Dendrocalamus and Bambusa. BaMV has a genome consisting of single-stranded, positive-sense RNA, about 6.4 kb in length. Nucleotide sequence analysis revealed five open reading frames (ORFs) in the genomic RNA of BaMV, as also found in other members of the potexvirus group. ORF1 encodes a 155 kD protein which contains an RNA-dependent RNA polymerase motif and is located at the 5' terminus. Gene for the 25 kD capsid protein is lying toward the 3' end. Triple gene blocks may be responsible for virus movement. In in vitro rabbit reticulocyte lysate (RRL) translation system, BaMV RNA directed the synthesis of one major 160 kD polypeptide, but failed to synthesize the viral capsid protein. Two subgenomic RNAs, 2.0 and 1.0 kb in length, could be detected in the infected cells. BaMV is unique in its ability to induce the formation of electron-dense crystalline bodies (EDCBs), in addition to virion aggregates, in the infected cells. EDCBs could be detected in the chloroplasts before virion aggregates are observed, and thus, can serve as infection initiation markers. At the later stage BaMV virions were seen to be attached to the chloroplasts with abundant occurrence of EDCBs free in the cytoplasm. Subsequently EDCBs were largely restricted to the cytoplasm and nuclei By immunoelectron microscopy, BaMV antigen was not detected in the chloroplasts, mitochondria or nuclei. Results also showed that EDCBs are serologically unrelated to capsid protein. However in in situ hybridization using digoxigenin-labelled in vitro transcript that covers the 3' terminal 173 NT of BaMV RNA as a riboprobe, BaMV RNA was found in large quantity within the chloroplasts, mitochondria and nuclei in infected cells. Recently, an isolate of BaMV from common bamboo (Bambusa vulgaris) (BaMV-V) was found to contain an RNA of 0.85 kb in length, besides the normal genomic RNA of 6.4 kb. Results of Northern blot analysis, infectivity assay and immunogold labelling suggested that this 0.85 kb RNA is a satellite RNA associated with BaMV. Unlike satellite RNAs of other plant viruses, this satellite RNA contains open an reading frame for a unique 20 kD nonstructural protein found among the vitro translation This satellite is the first one known to be associated with potexvirus group.

並列關鍵字

bamboo mosaic virus ； potexvirus ； satellite RNA