Dataset Information

Innate Immunity Activation and RNAi Interplay in Citrus Exocortis Viroid-Tomato Pathosystem.

ABSTRACT: Although viroids are the smallest and simplest plant pathogens known, the molecular mechanisms underlying their pathogenesis remain unclear. To unravel these mechanisms, a dual approach was implemented consisting of in silico identification of potential tomato silencing targets of pospiviroids, and the experimental validation of these targets through the sequencing of small RNAs and RNA ends extracted from tomatoes infected with a severe isolate of Citrus exocortis viroid (CEVd). The generated RNA ends were also used to monitor the differentially-expressed genes. These analyses showed that when CEVd symptoms are well established: (i) CEVd are degraded by at least three Dicer-like (DCL) proteins and possibly by RNA-induced silencing complex (RISC), (ii) five different mRNAs are partially degraded through post-transcriptional gene silencing (PTGS), including argonaute 2a, which is further degraded in phasiRNAs, (iii) Dicer-like 2b and 2d are both upregulated and degraded in phasiRNAs, and (iv) CEVd infection induced a significant shift in gene expression allowing to explain the usual symptoms of pospiviroids on tomato and to demonstrate the constant activation of host innate immunity and systemic acquired resistance (SAR) by these pathogenic RNAs. Finally, based on in silico analysis, potential immunity receptor candidates of viroid-derived RNAs are suggested.

SUBMITTER: Thibaut O

PROVIDER: S-EPMC6266551 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Innate Immunity Activation and RNAi Interplay in Citrus Exocortis Viroid-Tomato Pathosystem.

Thibaut Olivier O Claude Bragard B

Viruses 20181026 11

Although viroids are the smallest and simplest plant pathogens known, the molecular mechanisms underlying their pathogenesis remain unclear. To unravel these mechanisms, a dual approach was implemented consisting of <i>in silico</i> identification of potential tomato silencing targets of pospiviroids, and the experimental validation of these targets through the sequencing of small RNAs and RNA ends extracted from tomatoes infected with a severe isolate of <i>Citrus exocortis viroid</i> (CEVd). T ...[more]

PMID: 30373191

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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

Innate Immunity Activation and RNAi Interplay in Citrus Exocortis Viroid-Tomato Pathosystem.

Publications

Innate Immunity Activation and RNAi Interplay in Citrus Exocortis Viroid-Tomato Pathosystem.

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