Citrus Leprosis Virus C Encodes Three Proteins With Gene Silencing Suppression Activity

[EN] Citrus leprosis virus C (CiLV-C) belongs to the genusCilevirus, familyKitaviridae, and is considered the most devastating virus infecting citrus in Brazil, being the main viral pathogen responsible for citrus leprosis (CL), a severe disease that affects citrus orchards in Latin America. Here, proteins encoded by CiLV-C genomic RNA 1 and 2 were screened for potential RNA silencing suppressor (RSS) activity by five methods. Using the GFP-based reporter agroinfiltration assay, we have not found potential local suppressor activity for the five CiLV-C encoded proteins. However, when RSS activity was evaluated using the alfalfa mosaic virus (AMV) system, we found that the p29, p15, and p61 CiLV-C proteins triggered necrosis response and increased the AMV RNA 3 accumulation, suggesting a suppressive functionality. From the analysis of small interfering RNAs (siRNAs) accumulation, we observed that the ectopic expression of the p29, p15, and p61 reduced significantly the accumulation of GFP derived siRNAs. The use of the RSS defective turnip crinkle virus (TCV) system revealed that only thetrans-expression of the p15 protein restored the cell-to-cell viral movement. Finally, the potato virus X (PVX) system revealed that the expression of p29, p15, and p61 increased the PVX RNA accumulation; in addition, the p29 and p15 enhanced the pathogenicity of PVX resulting in the death of tobacco plants. Furthermore, PVX-p61 infection resulted in a hypersensitive response (HR), suggesting that p61 could also activate a plant defense response mechanism. This is the first report describing the RSS activity for CiLV-C proteins and, moreover, for a member of the familyKitaviridae.This work was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), proc. 2014/0845-9, 2017/50222-0, 2015/10249-1, and 2017/19898-8. This work was also supported by Instituto para la Formacion y Aprovechamiento de Recursos Humanos, Becas IFARHU-SENACYT, contrato 270-2018-361, grant BIO2017-88321-R from the Spanish Agencia Estatal de Investigacion (AEI), Fondo Europeo de Desarrollo Regional (FEDER), and the Prometeo Program GV2015/010 from the Generalitat Valenciana.Leastro, MO.; Ortega Castro, DY.; Freitas-Astúa, J.; Kitajima, EW.; Pallás Benet, V.; Sanchez Navarro, JA. (2020). Citrus Leprosis Virus C Encodes Three Proteins With Gene Silencing Suppression Activity. Frontiers in Microbiology. 11:1-16. https://doi.org/10.3389/fmicb.2020.0123111611Anandalakshmi, R., Pruss, G. J., Ge, X., Marathe, R., Mallory, A. C., Smith, T. H., & Vance, V. 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