Submitted to: Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/13/2011
Publication Date: 9/20/2011
Citation: Hajeri, S., Ramadugu, C., Keremane, M.L., Ng, J., Lee, R.F., Vidalakis, G. 2011. In vivo generated Citrus exocortis viroid progeny variants display a range of phenotypes with altered levels of replication, systemic accumulation and pathogenicity. Virology. 417(2):400-409. DOI:10.1016/j.virol.2011.06.013 Interpretive Summary: In this study, the genomic diversity of in vivo generated Citrus exocortis viroid (CEVd) in citrus protoplasts was analyzed and compared with that of viroids from test tube grown young seedlings and greenhouse-grown mature plants. Common sites of mutation were observed in CEVd sequence variants from protoplasts, seedlings, and mature plants. The biological significance of some of the in vivo generated sequence variants were studied in citrus and other experimental hosts. Replication and movement of CEVd were the two important biological functions studied. While several previous studies have created variants of CEVd in the laboratory by site directed mutagenesis, this study used in vivo generated sequence variants to better understand the structure to function relationship in CEVd.
Technical Abstract: Citrus exocortis viroid (CEVd) exists as heterogeneous variants in plant hosts. We inoculated RNA transcripts from a CEVd cDNA clone into protoplasts, seedlings and mature plants of citrus and sequenced 240 in vivo generated progeny variants. Selected progeny variants were further used to evaluate their pathogenicity in three CEVd hosts. The first category of variants U30C, G128A and U182C were not infectious in all three hosts tested; the second category of variants G50A and 108U+, were infectious in all three hosts’ tested but reverted back to the wild-type CEVd sequence. The third category of variants (62 A+, U129A, A265G and U278A) had more severe symptoms than wild-type and is genetically stable. The possible effects of these mutations on specific secondary structures of the viroid RNA and their concomitant effects on the biological properties such as replication and systemic accumulation are discussed.