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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


Examination of the mechanism of superinfection exclusion by Citrus tristeza virus
S. FOLIMONOVA (1), O. Atallah (1), S. Kang (2) (1) University of Florida, U.S.A.; (2) University of Florida, U.S.A.

Superinfection exclusion (SIE), referred to as cross-protection when used as an agricultural practice, is a phenomenon in which a primary virus infection prevents a secondary infection with the same or closely related virus. Earlier we demonstrated that SIE by Citrus tristeza virus requires viral p33 protein, yet p33 alone is not sufficient for virus exclusion. In this study we show that a 5’-proximal genomic region encoding leader proteases L1 and L2 is involved in SIE. Substitution of this region with the cognate sequences from a heterologous strain affected virus ability to exclude the parental virus. As the next step, we are interested to assess whether SIE is conferred by the L1/L2 proteins or by their coding sequences. We created four mutant viruses having alterations in the RNA sequences of the L1 and L2 N-terminal (NTD) and protease domains by changing the wobble base of each possible codon to avoid changing the amino acid sequences of these proteins. All mutant viruses were able to replicate in Nicotiana benthamiana at the levels comparable to the wild type virus, and three of them except L1 NTD mutant were able to establish systemic infection in N. benthamiana and citrus plants. Additional constructs containing mutations within the L1 NTD domain are being made with the goal to produce virus variants capable of systemic infection of both plant hosts. The effect of the introduced mutations in the L1-L2 domains on SIE ability will be assessed.