Functional Dissection of Naturally Occurring Amino Acid Substitutions in eIF4E That Confers Recessive Potyvirus Resistance in Plants

Abstract

Naturally existing variation in the eukaryotic translation initiation factor 4E (eIF4E) homolog encoded at the pvr1 locus in Capsicum results in recessively inherited resistance against several potyviruses. Previously reported data indicate that the physical interaction between Capsicum-eIF4E and the viral genome-linked protein (VPg) is required for the viral infection in the Capsicum-Tobacco etch virus (TEV) pathosystem. In this study, the potential structural role(s) of natural variation in the eIF4E protein encoded by recessive resistance alleles and their biological consequences have been assessed. Using highresolution three-dimensional structural models based on the available crystallographic structures of eIF4E, we show that the amino acid substitution G107R, found in many recessive plant virus resistance genes encoding eIF4E, is predicted to result in a substantial modification in the protein binding pocket. The G107R change was shown to not only be responsible for the interruption of VPg binding in planta but also for the loss of cap binding ability in vitro, the principal function of eIF4E in the host. Overexpression of the Capsicum-eIF4E protein containing the G107R amino acid substitution in Solanum lycopersicum indicated that this polymorphism alone is sufficient for the acquisition of resistance against several TEV strains.

Two Arabidopsis Loci Encode Novel Eukaryotic Initiation Factor 4E Isoforms That Are Functionally Distinct from the Conserved Plant Eukaryotic Initiation Factor 4E

“…S1). Residues that have been identified as being involved in cap binding from crystal structures of wheat (Triticum aestivum; Monzingo et al, 2007) and pea (Pisum sativum) eIF4E (Ashby et al, 2011) or by mutational analysis (Yeam et al, 2007;GermanRetana et al, 2008) are well conserved in eIF4E1b-type proteins. One exception is the conserved positively charged residue at K78, which is predicted in the wheat eIF4E crystal structure to stabilize the negatively charged phosphate backbone of the cap structure.…”

“…Residues marked # are conserved residues involved in interaction with eIF4G identified in yeast (Gross et al, 2003). Residues marked + are experimentally determined to be essential for cap binding (Yeam et al, 2007;German-Retana et al, 2008). Residues marked * are predicted to be involved in cap binding in plant eIF4E crystal structures (Monzingo et al, 2007;Ashby et al, 2011), and the residue marked^is predicted from the wheat eIF4E structure to form a salt bridge with the negatively charged phosphate backbone of the cap.…”

Arabidopsis thaliana class II poly(A)-binding proteins are required for efficient multiplication of turnip mosaic virus

“…VPg for one or the other of the eIF4E isoforms (Khan et al, 2006;Léonard et al, 2000;Yeam et al, 2007). The important structural differences found in the two eIF4F isoforms probably make it difficult to maintain interaction with both isomers.…”

Current advances and prospectus of viral resistance in horticultural crops

“…The eukaryotic translation factor 4E (eIF4E) plays a major role in the initiation of host translation by recruiting messenger RNAs to the ribosomal complex and has been repeatedly identified as an essential host factor required for viral infection (Truniger and Aranda 2009). Natural variation in eIF4E preventing viral sequestration confers effective resistance to potyvirus infection in multiple crop species, suggesting that the alteration of host factors such as translation-initiation factors is a common strategy for developing viral resistance in plants (Schaad et al 2000;Yeam et al, 2007;Cavatorta et al, 2008). Those factors include pvr1 (pvr2) in pepper, mo1 in lettuce, sbm1 in pea, rym4/5 in barley, pot1 in tomato, and zym-FL in watermelon (Gao et al, 2004;Ling et al, 2009;Nicaise et al, 2003;Ruffel et al, 2002;Kang et al, 2005a;Wicker et al, 2005).…”