台灣瓜類褪綠黃化病毒之分子特性分析

Molecular characterization of Cucurbit chlorotic yellows virus from Taiwan

"瓜類褪綠黃化病毒（Cucurbit chlorotic yellows virus，CCYV）首度於20 0 4年在日本發現，直到20 1 0年才被確認為Closteroviridae科中Crinivirus屬的新種。Criniviruses局限於染病植物的韌皮部組織，且由粉蝨以半永續性的方式傳播。Criniviruses的基因組由兩條正極性單股RNA所組成，稱為RNA-1和RNA-2，且分別被包裹在大小約650-900×12 nm的病毒顆粒中。近年來，CCYV造成台灣洋香瓜及西瓜產業的嚴重損失。本研究完成雲林縣崙背鄉洋香瓜田的CCYV分離株（CCYV-LB）之全基因組定序，結果顯示，CCYV-LB的RNA-1和RNA-2分別有8,607和8,041個核苷酸（nucleotide，nt）。CCYVLB的RNA-1具有四個讀取框（open reading frames，ORFs），包含1a、1b（RNA-dependent RNA polymerase，RdRp）、P6和P2。其RNA-2含有8個讀取框，分別為P5、熱休克同源蛋白70（heat shock protein 70 homologue，Hsp70h）、P6、P60、P9、主要外鞘蛋白（coat protein，CP）、次要外鞘蛋白（minor coat protein，CPm）和P26。序列分析結果顯示，CCYV-LB的RNA-1和RNA-2序列與日本和中國已知的CCYV分離株分別具有99.7-100.0%和99.7-99.8%的核苷酸相同度。在Crinivirus屬分類依據的蛋白RdRp、Hsp70h和CP親緣關係分析上，CCYV與菜豆黃化失調病毒（Bean yellow disorder virus）和萵苣褪綠病毒（Lettuce chlorosis virus）的演化關係最為相近。"

"Cucurbit chlorotic yellows virus (CCYV), first discovered in Japan in 2004, has been clarified as a new species of the genus Crinivirus in the family Closteroviridae since 2010. Criniviruses are phloem-limited in the infected plants and semi-persistently transmitted by whiteflies. The bipartite positive-sense singlestranded genomic RNAs of criniviruses are individually encapsidated in two separate flexuous particles of 650-900 × 12 nm, denoted RNA-1 and RNA-2. In recent years, CCYV caused serious damages to the production of melon and watermelon in Taiwan. In this study, whole genome sequence of a CCYV isolate LB collected from a melon field in Lunbei Township of Yunlin County was determined. Our results indicated that CCYV Lunbei (LB) isolate RNA-1 and RNA-2 are 8,607 and 8,041 nucleotides (nt) in length, respectively. The CCYV-LB RNA-1 consists of four open reading frames (ORFs), 1a, 1b (RNA-dependent RNA polymerase, RdRp), P6 and P22. The CCYV-LB RNA-2 comprises eight ORFs, including P5, heat shock protein 70 homologue (Hsp70h), P6, P60, P9, major coat protein (CP), minor coat protein (CPm) and P26. Sequence analyses revealed that the RNA-1 and RNA-2 sequences of CCYV-LB share 99.7100% and 99.7-99.8% nt identity, respectively, with those of other known isolates of CCYV in Japan and China. Phylogenetic analyses of the sequences of RdRp, Hsp70h and CP among Crinivirus species indicated that CCYV is closely related to Bean yellow disorder virus and Lettuce chlorosis virus."