|Folimonova, Svetlana - UNIVERSITY OF FLORIDA|
|Folimonov, Alexey - UNIVERSITY OF FLORIDA|
|Dawson, William - UNIVERSITY OF FLORIDA|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 14, 2008
Publication Date: July 1, 2008
Citation: Folimonova, S.Y., Folimonov, A.S., Tatineni, S., Dawson, W.O. 2008. Citrus tristeza virus: survival at the edge of the movement continuum. Journal of Virology, Volume 82, page 6546-6556. Interpretive Summary: Citrus tristeza virus (CTV) is the most economically important viral disease of citrus in US and worldwide. Virus movement and infection process of citrus trees by CTV was poorly examined. In this study, using the green fluorescent protein-tagged virus, the movement of CTV was examined in several citrus hosts that are differentially susceptible. In susceptible Citrus macrophylla plants, CTV infects a cluster of 3 to more than12 cells, where as in less susceptible sour orange plants virus is restricted to mostly single cells. This study suggests that CTV has limited cell-to-cell movement in susceptible hosts and essentially no cell-to-cell movement in less susceptible hosts. In sour orange plants the virus appears to survive with only the long-distance movement.
Technical Abstract: Systemic invasion of plants by viruses is thought to involve two processes: cell-to-cell movement between adjacent cells and long-distance movement that allows the virus to rapidly move through sieve elements and unload at the growing parts of the plant. There is a continuum of proportions of these processes that determines the degrees of systemic infection of different plants by different viruses. We examined the systemic distribution of Citrus tristeza virus (CTV) in citrus species with a range of susceptibility. By using a ‘pure’ culture of CTV from a cDNA clone and green fluorescent protein-labeled virus we show that both cell-to-cell and long distance movement are unusually limited, and the degree of limitation varies depending on the citrus host. In the more susceptible hosts CTV infected only a small portion of phloem associated cells, and, moreover, the number of infection sites in less susceptible citrus species was substantially decreased further, indicating that long-distance movement mechanism was reduced in those hosts. Analysis of infection foci in the two most differential citrus species, C. macrophylla and sour orange, revealed that in the more susceptible host the infection foci were composed of a cluster of multiple cells, while in the less susceptible host infection foci were usually single cells, suggesting that essentially no cell-to-cell movement occurred in the latter host. Thus, CTV in sour orange represents a pattern of systemic infection in which the virus appears to function with only the long-distance movement mechanism, yet is able to survive in nature.