Characterization of Passionfruit Crinkle Potyvirus - a Newly Found Virus Infecting Passionfruit

Abstract

A virus, designated as passionfruit crinkle potyvirus (PCV), was isolated from passionfruit cultivar Tainung No. 1 causing crinkle symptom on the foliage, different from those induced by the passionfruit mottle (PaMV) and passionfruit woodiness potyviruses (PWV). Unlike PaMV and PWV, PCV did not produce any visible symptom on the fruits. It was identified as a potyvirus on the basis of particle morphology, aphid transmissibility, and the ability to induce cytoplasinic cylindrical inclusions (CI) in infectedcells. Of thirty six species in six plant families inoculated, PCV infected 15 species of Passifloraceae, Chenopodiaceae, Leguminosae, Solanaceae, and Amaranthaceae, but all the species tested in Cucurbitaceae were not infected by PCV, indicating that it had wider host range than PaMV and PWV. In light microscopy, large aggregates of bundle-shaped cylindrical inclusions, similar to those induced by PaMV were found accumulated in the cytoplasm of PCV-infected cells. Purified virions and the cylindrical inclusion protein (CIP) were obtained by equilibrium centrifugation in Cs2SO4 and preparative electrophoresis, respectively. As analysed in sodium dodecyl sulfate (SDS) electrophoresis, the relative molecular mass for the capsid and CIP monomer of PCV were estimated to be 35 and 79kDa, respectively. In reciprocal SDS-immun-odiffusion and ELISA tests, PCV was found serologically indistinguishable to a potyvirus isolate originating from passionfruit in Puerto Rico, related to, but distinct from, PWV and peanut stripe potyvirus, while it was unrelated to PaMV and 11 other potyviruses. 本研究由本省台農一號百香果分離獲得一種與文獻上所記錄之百香果木質化病毒（passionfruit woodiness Potyvirus, PWV）及百香果班紋病毒(passionfruit mottle potyvirus, PaMV)性質迴異之馬鈴薯Y屬病毒。此病毒株系感染台農一號百香果時僅在葉部產生漣葉(crinkle)病徵，對果實之外型與著色並無任何影響。此種病徵與PWV及PaMV所造成者有顯著差異，因此將其定名為百香果漣葉病毒(passionfruit crinkle potyvirus)簡稱PCV。PCV具長絲狀易彎曲型顆粒(elongated flexuous rods)，可由桃蚜以非永續型方式(non-persistent manner)傳播，於感病細胞質中可產生圓柱狀內含體(cylindrical inclusion)。在所接種之6科36種值物中只有葫蘆科之瓜類植物不能被PCV感染，顯示其寄主範圍較PWV及PaMV寬廣。另外PCV可於大豆(Glycine max (L.) Merr.)及千日紅(Gomphrcna globosa L.)感染造成系統性病徵之特性也與PWV及PaMV不同。利用交叉保護汰亦證實PCV無法保護百香果免於PWV及PaMv之重複感染。以高低速交替離心(differential centrifugation)及平衡離心法(equilibrium centrifugation)可順利將PCV病毒顆粒由百香果葉片中純化。純化試料經電泳分析估計其鞘蛋白基本單位(capsid protein subunit)之分子量為35kDa。在純化病毒顆粒之過程中可同時純化出PCV於感病細胞質內所合成之圓柱狀內含體蛋白(cylindrical inclusion protein, CIP)，其分子量則估計為79kDa。將純化之病毒顆粒及CIP進行免疫注射於家兔體內已製成專一性抗體。將此等抗體應用於SDS免疫擴散反應(SDS-immunodiffusion test）及酵聯抗體法(ELISA)測試，發現PCV與PaMv無任何血清類緣關係，而PCV雖與PWV有部份血緣關係但彼此間仍有顯著差異，但PCV之血清學性質與Bird et al. (1991)自波多黎各百香果所分離而未充分鑑定之Puerto Rico passionfruit potyviru則完全相同無法區別。另外與其他12種已知之馬鈴薯Y屬病毒比較時，發現PCV只與落花生條斑病毒(peanut stripe polyvirus, PStV)有部份血緣關係，而與其他11種病毒無任何血緣關係。由現有證據顯示PCV與過去在百香果上已記錄之數種馬鈴薯Y屬病毒之特性有明顯差異，而與其他已知之病毒亦呈顯茗之不同，故應屬一種尚未經充分鑑定之新病毒。