Variability in eukaryotic initiation factor iso4E in Brassica rapa influences interactions with the viral protein linked to the genome of Turnip mosaic virus

Guoliang Li,Xiaowu Wang,Shifan Zhang,Shujiang Zhang,Hui Zhang,Wei Qian,Rifei Sun,Jian Wu,Fei Li,Zhiyuan Fang

doi:10.1038/s41598-018-31739-1

Abstract

Plant potyviruses require eukaryotic translation initiation factors (eIFs) such as eIF4E and eIF(iso)4E to replicate and spread. When Turnip mosaic virus (TuMV) infects a host plant, its viral protein linked to the genome (VPg) needs to interact with eIF4E or eIF(iso)4E to initiate translation. TuMV utilizes BraA.eIF4E.a, BraA.eIF4E.c, BraA.eIF(iso)4E.a, and BraA.eIF(iso)4E.c of Brassica rapa to initiate translation in Arabidopsis thaliana. In this study, the BraA.eIF4E.a, BraA.eIF4E.c, BraA.eIF(iso)4E.a, and BraA.eIF(iso)4E.c genes were cloned and sequenced from eight B. rapa lines, namely, two BraA.eIF4E.a alleles, four BraA.eIF4E.c alleles, four BraA.eIF(iso)4E.a alleles, and two BraA.eIF(iso)4E.c alleles. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses indicated that TuMV VPg could not interact with eIF4E, but only with eIF(iso)4E of B. rapa. In addition, the VPgs of the different TuMV isolates interacted with various eIF(iso)4E copies in B. rapa. In particular, TuMV-UK1/CDN1 VPg only interacted with BraA.eIF(iso)4E.c, not with BraA.eIF(iso)4E.a. Some single nucleotide polymorphisms (SNPs) were identified that may have affected the interaction between eIF(iso)4E and VPg such as the SNP T106C in BraA.eIF(iso)4E.c and the SNP A154C in VPg. Furthermore, a three-dimensional structural model of the BraA.eIF(iso)4E.c-1 protein was constructed to identify the specific conformation of the variable amino acids from BraA.eIF(iso)4E.c. The 36th amino acid in BraA.eIF(iso)4E.c is highly conserved and may play an important role in establishing protein structural stability. The findings of the present study may lay the foundation for future investigations on the co-evolution of TuMV and eIF(iso)4E.

Highlights

Potyvirus is the largest genus of plant viruses and causes severe economic losses in agriculture[1,2]
Y2H assays and co-immunoprecipitation analysis suggest that the W95L, K150L, and W95L/K150E amino acid mutations in B. rapa eukaryotic translation initiation factors (eIFs)(iso)4E interrupt its interaction with Turnip mosaic virus (TuMV) viral protein linked to the genome (VPg) and its overexpression in a susceptible Chinese cabbage cultivar confers resistance to multiple TuMV strains[50]
We previously showed that TuMV-C4 VPg interacts with BraA.eIF(iso)4E.a, but not with BraA.eIF(iso)4E.c, whereas TuMV-UK1 VPg only interacts with BraA.eIF(iso)4E.c, but not BraA.eIF(iso)4E. a53

Summary

Introduction

Potyvirus is the largest genus of plant viruses (comprising approximately 36% of the total number of plant viruses) and causes severe economic losses in agriculture[1,2]. The passive mechanisms of plant virus resistance indicate that loss, deletion, or mutation of a required host factor may cause recessive resistance to the virus[2,12,13] Several of these resistance genes (such as pvr[1] in Capsicum and retr[01] and retr[02] in Brassica rapa) have been successfully used for decades in breeding programs as effective and stable sources of resistance[14,15,16]. Some recessive resistance genes to TuMV have been identified in B. rapa, such as retr0115 and retr0216, which encode eIF(iso)4E proteins. This may provide a foundation for the screening and cloning of eIF(iso)4E resistance loci, as well as systematic research into the resistance mechanisms of eIF(iso)4E to TuMV

Methods

Results

Conclusion