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The link between RNA structure, factor requirement and plant viral resistance.
J. Zhang (1), R. Roberts (1), L. Mayberry (2), S. Tatineni (3), K. Browning (2), A. RAKOTONDRAFARA (4). (1) University of Wisconsin-Madison, Madison, WI, U.S.A.; (2) University of Texas-Austin, Austin, TX, U.S.A.; (3) University of Nebraska-Lincoln, Lincoln, NE, U.S.A.; (4) University of Wisconsin - Madison, Madison, WI, U.S.A.

 Genetic resistance remains the best long-term strategy for combating viral diseases. Despite the direct link between plant resistance genes against many RNA viruses to host translation factors, it is astonishing how little we know on how these viruses are translated and how these resistance genes affect viral infection. Of particular interest, are the internal ribosome entry site (IRES) RNA sequences previously reported in the members of the largest family of plant viruses <i>Potyviridae</i>, which encompasses 30% of the most damaging viral diseases. These RNA are characterized by their small size, structural simplicity and requirement for most of the host translation factors to mimic the function of a cap structure. Our objective is to dissect the mechanism of translation of a newly emerging <i>Triticum mosaic virus</i> (TriMV), a member of <i>Potyviridae</i>, in wheat. Our preliminary results reveal that TriMV RNA has an atypically long and structured IRES RNA element, which corresponds to its 5’ leader sequence. Such features have not yet been described in plant viruses, while they are prominent in the animal counterparts. Remarkably, the element sustains 2 fold higher translation than a cellular-mimicking mRNA and 100-fold higher translation of that of previously reported <i>potyviral </i>IRESes. Such strong level of translation driven by a plant viral IRES has not yet been reported and raises many important questions in efficiency of disease resistance targeting translation.

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