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Two nucleotide positions in the Citrus exocortis viroid RNA associated with symptom expression in Etrog citron but not in experimental herbaceous hosts.

ABSTRACT: Citrus exocortis viroid (CEVd) is the causal agent of exocortis disease of citrus. CEVd has a wide host range that includes woody and herbaceous species. A new CEVd strain (CEVd(COL)), phylogenetically clustering with CEVd variants of Class A inducing severe symptoms in tomato, was identified in Colombia and shown to induce only extremely mild symptoms in Etrog citron indicator plants. Using site-directed mutagenesis, two nucleotide substitutions (314A ? G and 315U ? A) in the lower strand of the P domain of the predicted CEVd(COL) secondary structure resulted in a severe artificial CEVd(MCOL) variant. Conversely, two nucleotide exchanges (314G ? A and 315A ? U) in the same region of the severe variant CEVd(E-117) resulted in a symptomless artificial CEVd(ME-117) variant. Infectivity assays conducted with the natural and mutated variants showed that all induced severe symptoms in Gynura aurantiaca, tomato and chrysanthemum. This is the first report of the identification of pathogenic determinants of CEVd in citrus, and shows that these pathogenicity determinants are host dependent.

SUBMITTER: Murcia N

PROVIDER: S-EPMC6640353 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Two nucleotide positions in the Citrus exocortis viroid RNA associated with symptom expression in Etrog citron but not in experimental herbaceous hosts.

Murcia Nubia N Bernad Lucía L Duran-Vila Núria N Serra Pedro P

Molecular plant pathology 20101001 2

Citrus exocortis viroid (CEVd) is the causal agent of exocortis disease of citrus. CEVd has a wide host range that includes woody and herbaceous species. A new CEVd strain (CEVd(COL)), phylogenetically clustering with CEVd variants of Class A inducing severe symptoms in tomato, was identified in Colombia and shown to induce only extremely mild symptoms in Etrog citron indicator plants. Using site-directed mutagenesis, two nucleotide substitutions (314A → G and 315U → A) in the lower strand of th ...[more]

PMID: 21199569

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Project description:BackgroundTwo citrus viroids, Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd), have been reported and become potential threats to the citrus industry in Taiwan. The distributions and infection rates of two viroids have not been investigated since the two diseases were presented decades ago. The genetic diversities and evolutionary relationships of two viroids also remain unclear in the mix citrus planted region.MethodsMultiplex RT-PCR was used to detect the two viroids for the first time in seven main cultivars of citrus. Multiplex real-time RT-PCR quantified the distributions of two viroids in four citrus tissues. Sequence alignment and phylogenetic analysis were performed using the ClustalW and MEGA6 (neighbor-joining with p-distance model), respectively.ResultsHSVd was found more prevalent than CEVd (32.2% vs. 30.4%). Both CEVd and HSVd were commonly found simultaneously in the different citrus cultivars (up to 55%). Results of the multiplex quantitative analysis suggested that uneven distributions of both viroids with twig bark as the most appropriate material for studies involving viroid sampling such as quarantine inspection. Sequence alignment against Taiwanese isolates, along with analysis of secondary structure, revealed the existence of 10 and 5 major mutation sites in CEVd and HSVd, respectively. The mutation sites in CEVd were located at both ends of terminal and variability domains, whereas those in HSVd were situated in left terminal and pathogenicity domains. A phylogenetic analysis incorporating worldwide viroid isolates indicated three and two clusters for the Taiwanese isolates of CEVd and HSVd, respectively.ConclusionsModerately high infection and co-infection rates of two viroids in certain citrus cultivars suggest that different citrus cultivars may play important roles in viroid infection and evolution. These data also demonstrate that two multiplex molecular detection methods developed in the present study provide powerful tools to understand the genetic diversities among viroid isolates and quantify viroids in citrus host. Our field survey can help clarify citrus-viroid relationships as well as develop proper prevention strategies.

Dataset Information

Two nucleotide positions in the Citrus exocortis viroid RNA associated with symptom expression in Etrog citron but not in experimental herbaceous hosts.

Publications

Two nucleotide positions in the Citrus exocortis viroid RNA associated with symptom expression in Etrog citron but not in experimental herbaceous hosts.

Similar Datasets

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