The potyvirus recessive resistance gene, sbm1, identifies a novel role for translation initiation factor elF4E in cell-to-cell trafficking

Abstract

From the characterization of the recessive resistance gene, sbm1, in pea we have identified the eukaryotic translation initiation factor, elF4E, as a susceptibility factor required for infection with the Potyvirus, Pea seedborne mosaic virus. A functional analysis of the mode of action of the product of the dominant allele revealed a novel function for elF4E in its support for virus movement from cell-to-cell, in addition to its probable support for viral RNA translation, and hence replication. Different resistance specificities in two independent pea lines were explained by different mutations in elF4E. On the modelled structure of elF4E the coding changes were in both cases lying in and around the structural pocket involved in binding the 5′-m7G cap of eukaryotic mRNAs. Protein expression and cap-binding analysis showed that elF4E encoded by a resistant plant could not bind to m7G-Sepharose, a result which may point to functional redundancy between elF4E and the paralogous elF(iso)4E in resistant peas. These observations, together with related findings for other potyvirus recessive resistances, provide a more complete picture of the potyvirus life cycle.