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United States Department of Agriculture

Agricultural Research Service

Title: Cloning and Sequence Analysis of a Citrus Yellow Mosaic Virus Genome Infectious to Sweet Orange Via Agrobacterium-Mediated Inoculation

Authors
item Huang, Qi
item Hartung, John

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 29, 2001
Publication Date: N/A

Interpretive Summary: Citrus Yellow Mosaic is a disease of sweet orange in India, and is caused by a virus of the same name. Symptoms of the disease include a bright yellow mosaic symptom that becomes stronger as leaves age. The disease is serious, causing a reduction in fruit quantity and quality. Severely affected trees are not productive and are removed. We have worked with the virus under quarantine to better understand its biology and to develop methods to prevent its introduction into the United States. We have determined the complete nucleotide sequence of the virus genome and compared it to other related viruses. CYMV is most closely related to Cacao Swollen Shoot Virus, and is not as closely related to sugarcane bacilliform virus, which is widespread in the United States. We have developed a preliminary sensitive and specific assay for the virus based on this sequence data. We have also engineered the virus so that we can grow it in bacteria in laboratory culture, and then introduce it into sweet orange with the assistance of these special bacteria. This will allow us in the future to make mutations in individual virus genes and then test the effects of the mutations in sweet orange. This will allow us to define the virus genes that are minimally required for infection and pathogenesis. Both the virus and its components have excellent potential to be modified as a tool in plant biotechnology. This work will be of interest to the international scientific community, plant health regulatory officials, and to workers in India interested in controlling the disease.

Technical Abstract: Citrus Yellow Mosaic virus causes citrus mosaic disease commonly occurring in India. It belongs to the genus Badnavirus. We have cloned the CYMV genome and determined its complete nucleotide sequence. The genome is 7559 bp in length and contains six putative open reading frames (ORFs), all on the plus-strand, each capable of encoding proteins greater than 10 kDa. The largest ORF, number 3, encodes a putative polyprotein for functions involved in viral movement, assembly and replication. The other ORFs encode proteins whose exact functions are incompletely understood. The genome also contains a plant tRNAmet-binding site in its intergenic region that may serve as a primer for minus-strand DNA synthesis. Phylogenetic analysis of the badnaviruses revealed that CYMV is most closely related to cacao swollen shoot virus. We have demonstrated that a construct containing 1.4 copies of the cloned CYMV genome can infect sweet orange via Agrobacterium-mediated inoculation.

Last Modified: 10/23/2014
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