Submitted to: International Organization of Citrus Virologists Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/8/2006
Publication Date: 1/10/2007
Citation: Guerra-Moreno, A.S., Keremane, M.L., Brlansky, R.H., Lee, R.F. 2007. Citrus Leprosis Symptoms Can be Associated with the Presence of Two Different Viruses: Cytoplasmic and Nuclear, the Former Having a Multipartite RNA Genome. International Organization of Citrus Virologists Proceedings, 16th Conference, Pgs. 230-239. Interpretive Summary: Citrus leprosis is an emerging disease that has recently moved into Central America and the Caribbean Basin area and threatens North American citrus production. The virus associated with leprosis disease has not been characterized previously, but prior electron microscopy results suggest there are two virus types associated with leprosis disease: one virus located in the cytoplasm and another virus located in the nucleus. We report here the partial characterization of the genome of the cytoplasmic virus (cytoplasmic citrus leprosis virus); a positive-sense RNA virus with a bi-partite genome. Using probes specific for the cytoplasmic citrus leprosis virus, we demonstrate that the virus in the nucleus of plants showing leprosis symptoms is not related to the virus in the cytoplasm. The cytoplasmic and nuclear types of leprosis are probably caused by two distinct viruses.
Technical Abstract: Citrus leprosis has been present in several South American countries for many decades. Its recently reported emergence in Central American countries presents a serious threat to citrus in the Caribbean Basin, Central and North America. Cyto- and nucleo-rhabdovirus-like particles have been associated with citrus leprosis previously by electron microscopy. Screening and sequencing of clones from a cDNA library made from a total RNA extraction from cytoplasmic-leprosis infected tissue has led to the identification of some putative viral sequences. Northern hybridizations have shown consistent association of these putative viral sequences with the cytoplasmic-type leprosis from Panama, but not with the nuclear-type or with healthy citrus. Northern hybridizations using DIG-labeled DNA and RNA (sense and antisense) probes of different clones have shown two different patterns suggesting two RNAs associated with cytoplasmic-leprosis infected tissue: RNA 1 and RNA 2. Probes of clones from RNA 1 hybridized with two RNAs of approximately 10 kb and 1.2 kb, while probes of clones from RNA 2 hybridized with four RNAs of approximately 4.7, 2.5, 1.6, and 1.0 kb. These results suggest that at least two species of RNAs are associated with leprosis infected tissue where only cytoplasmic type particles may be detected by transmission electron microscopy, and that the cytoplasmic- and that nuclear-type of leprosis are probably caused by two distinct viruses.