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Oral: Virus-Host Interactions


Determination and characterization of a symptom determinant of Grapevine fanleaf virus
L. OSTERBAAN (1), L. Osterbaan (1), M. Fuchs (1) (1) Section of Plant Pathology and Plant-Microbe Biology, Cornell University, New York State Agricultural Experiment Station, U.S.A.

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Grapevine fanleaf virus (GFLV) -the causative agent of fanleaf degeneration- is one of the most devastating viral diseases of grapevines. GFLV is a bipartite (+) sense RNA nepovirus and is transmitted by the ectoparasitic nematode Xiphinema index. The five proteins encoded by RNA1 are associated with replication and protein maturation, while the three proteins encoded by RNA2 are involved in replication, cell-to-cell movement, and genome encapsidation. Infected vines exhibit a variety of symptoms, including shortened internodes, fan-like (deeply lobed) leaves, mosaic, and vein yellowing. Infected vines have decreased fruit yield and quality, and also a shortened productive lifespan. Little is known about the host-pathogen interactions leading to symptom development. Recent work with chimeras of symptomatic and asymptomatic strains of GFLV (strains GHu and F13, respectively) in the plant model species Nicotiana benthamiana has shown that symptom development in this host species is dependent on a 408-nucleotide sequence at the 3’ end of RNA1 of GFLV-GHu. A reverse genetics approach was used to characterize the symptom determinant by using agroinoculation to establish infection with a series of recombinant GFLV genomes in planta and thus determine the minimal GFLV-GHu sequence necessary for symptom development in N. benthamiana. A better understanding of GFLV’s biology will inform the mechanism by which the virus causes symptoms in its hosts.