LreEF1A4, a Translation Elongation Factor from Lilium regale, Is Pivotal for Cucumber Mosaic Virus and Tobacco Rattle Virus Infections and Tolerance to Salt and Drought

Abstract

Eukaryotic translation elongation factors are implicated in protein synthesis across different living organisms, but their biological functions in the pathogenesis of cucumber mosaic virus (CMV) and tobacco rattle virus (TRV) infections are poorly understood. Here, we isolated and characterized a cDNA clone, <i>LreEF1A4,</i> encoding the alpha subunit of elongation factor 1, from a CMV-elicited suppression subtractive hybridization library of <i>Lilium regale</i>. The infection tests using CMV remarkably increased transcript abundance of <i>LreEF1A4</i>; however, it also led to inconsistent expression profiles of three other LreEF1A homologs (<i>LreEF1A1-3</i>). Protein modelling analysis revealed that the amino acid substitutions among four LreEF1As may not affect their enzymatic functions. <i>LreEF1A4</i> was ectopically overexpressed in petunia (<i>Petunia hybrida</i>), and transgenic plants exhibited delayed leaf and flower senescence, concomitant with increased transcription of photosynthesis-related genes and reduced expression of senescence-associated genes, respectively. A compromised resistance to CMV and TRV infections was found in transgenic petunia plants overexpressing <i>LreEF1A4</i>, whereas its overexpression resulted in an enhanced tolerance to salt and drought stresses. Taken together, our data demonstrate that <i>LreEF1A4</i> functions as a positive regulator in viral multiplication and plant adaption to high salinity and dehydration.