Chakraborty S, Vanitharani R, Chattopadhyay B, Fauquet C M
International Laboratory for Tropical Agricultural Biotechnology, Donald Danforth Plant Science Center, 975 N. Warson Road, St Louis, MO 63132, USA.
J Gen Virol. 2008 Mar;89(Pt 3):818-828. doi: 10.1099/vir.0.82873-0.
Isolates of two distinct begomovirus species, the severe strain of the species Tomato leaf curl New Delhi virus (tomato leaf curl New Delhi virus-[India:New Delhi:Severe:1992]; ToLCNDV-[IN:ND:Svr:92], bipartite) and the Varanasi strain of the species Tomato leaf curl Gujarat virus (tomato leaf curl Gujarat virus-[India:Varanasi:2001]; ToLCGV-[IN:Var:01], mono/bipartite) infect tomato (Lycopersicon esculentum) and cause severe yield losses in northern India. This study investigated the infectivity properties of genomic components of these two species. Both pseudorecombinants were infectious in Nicotiana benthamiana, Nicotiana tabacum and L. esculentum. Enhanced pathogenicity was observed when DNA-A of ToLCNDV-[IN:ND:Svr:92] was trans-complemented with ToLCGV-[IN:Var:01] DNA-B, and was consistently associated with an increase in accumulation of ToLCGV-[IN:Var:01] DNA-B. Mixed infection of ToLCNDV-[IN:ND:Svr:92] and ToLCGV-[IN:Var:01] always showed extremely severe symptoms, suggesting a synergistic interaction between these two viruses. Southern blot analysis of viral DNAs from infected plants showed a significantly higher level of accumulation of both ToLCNDV components and DNA-B of ToLCGV-[IN:Var:01] with no alteration to levels of DNA-A of ToLCGV-[IN:Var:01]. Symptom development and/or higher infectivity of the supervirulent pseudorecombinants correlated with the increased levels of DNA-B accumulation. Protoplast replication assays revealed that enhanced infectivity by the pseudorecombinant occurred at the level of replication, as DNA-A of ToLCNDV-[IN:ND:Svr:92] enhanced ToLCGV-[IN:Var:01] DNA-B replication, whose accumulation was in turn increased by ToLCGV-[IN:Var:01] DNA-A. This is the first report demonstrating a virulent pseudorecombinant between two distinct species of begomoviruses that infect tomato, and is the second report on synergism between begomoviruses. The results revealed that ToLCGV-[IN:Var:01] DNA-B is capable of associating with different DNA-A components, despite having different iteron sequences.
两种不同的双生病毒物种的分离株，即番茄卷叶新德里病毒（番茄卷叶新德里病毒-[印度：新德里：严重：1992]；ToLCNDV-[IN:ND:Svr:92]，二分体）的严重毒株和番茄卷叶古吉拉特病毒（番茄卷叶古吉拉特病毒-[印度：瓦拉纳西：2001]；ToLCGV-[IN:Var:01]，单分体/二分体）的瓦拉纳西毒株，可感染番茄（番茄）并在印度北部造成严重的产量损失。本研究调查了这两个物种基因组组分的感染特性。两种假重组体在本氏烟草、烟草和番茄中均具有感染性。当ToLCNDV-[IN:ND:Svr:92]的DNA-A与ToLCGV-[IN:Var:01]的DNA-B进行反式互补时，观察到致病性增强，并且始终与ToLCGV-[IN:Var:01]的DNA-B积累增加相关。ToLCNDV-[IN:ND:Svr:92]和ToLCGV-[IN:Var:01]的混合感染总是表现出极其严重的症状，表明这两种病毒之间存在协同相互作用。对感染植物的病毒DNA进行Southern杂交分析显示，ToLCNDV的两个组分以及ToLCGV-[IN:Var:01]的DNA-B积累水平显著更高，而ToLCGV-[IN:Var:01]的DNA-A水平没有变化。超强毒假重组体的症状发展和/或更高的感染性与DNA-B积累水平的增加相关。原生质体复制试验表明，假重组体增强的感染性发生在复制水平，因为ToLCNDV-[IN:ND:Svr:92]的DNA-A增强了ToLCGV-[IN:Var:01]的DNA-B复制，而ToLCGV-[IN:Var:01]的DNA-A又反过来增加了其积累。这是第一份证明感染番茄的两种不同双生病毒物种之间存在强毒假重组体的报告，也是关于双生病毒之间协同作用的第二份报告。结果表明，尽管ToLCGV-[IN:Var:01]的DNA-B具有不同的重复序列，但它能够与不同的DNA-A组分结合。
