Cell-to-Cell and Long Distance Signaling
Zhong, Xuehua , Tao, Xiaorong , Stombaugh, Jesse , Leontis, Neocles , Ding, Biao .
Tertiary Structural and Functional Analyses Identify a Viroid RNA Motif that Mediates Vascular Entry.
Vascular entry is a decisive step for the initiation of long distance movement of viral and viroid RNAs, systemic silencing signals, and developmental/defense signals. The molecular mechanisms that regulate vascular entry of any RNAs remain poorly understood. In particular, the role of an RNA itself is unknown. We used Potato spindle tuber viroid (PSTVd), a noncoding and infectious RNA, as a model to investigate the direct role of an RNA in vascular entry. We report here the identification of a motif that is required for PSTVd to traffic from the bundle sheath into the vascular tissue to initiate systemic infection. This motif is not required for trafficking from the inoculated epidermis to mesophyll and bundle sheath. This motif consists of U43 and C318 that interact by cis Watson Crick-Watson Crick base pairing with water insertion, flanked by short helices that comprise regular Watson Crick-Watson Crick base pairs. This tertiary structural model was inferred by comparative sequence analysis and comparison with X-ray crystal structures of similar motifs in rRNAs. It is further supported by co-variation analyses, mutagenesis based on Isostericity Matrix, and functional characterization of mutants. Our results provide the first loss-of-function genetic evidence that a specific RNA motif is required for vascular entry to initiate systemic trafficking. They support the hypothesis that tissue-specific factors interact with distinct RNA motifs to control trafficking across specific cellular boundaries. Furthermore, our model and approaches should have broad implications to investigate the structural motifs in endogenous and infectious RNAs critical for vascular entry.
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1 - The ohio state university, plant cellular and molecular biology, 1060 Carmack Rd., Columbus, OH, 43210, USA
2 - The ohio state university, plant cellular and molecular biology
3 - Bowling Green State University, Department of chemistry and center for biomolecular sciences
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM