title: Multiple copies of eukaryotic translation initiation factors in Brassica rapa facilitate redundancy, enabling diversification through variation in splicing and broad-spectrum virus resistance.
abstract: Recessive strain-specific resistance to a number of plant viruses in the Potyvirus genus has been found to be based on mutations in the eukaryotic translation initiation factor 4E (eIF4E) and its isoform, eIF(iso)4E. We identified three copies of eIF(iso)4E in a number of Brassica rapa lines. Here we report broad-spectrum resistance to the potyvirus Turnip mosaic virus (TuMV) due to a natural mechanism based on the mis-splicing of the eIF(iso)4E allele in some TuMV-resistant B. rapa var. pekinensis lines. Of the splice variants, the most common results in a stop codon in intron 1 and a much truncated, non-functional protein. The existence of multiple copies has enabled redundancy in the host plant's translational machinery, resulting in diversification and emergence of the resistance. Deployment of the resistance is complicated by the presence of multiple copies of the gene. Our data suggest that in the B. rapa subspecies trilocularis, TuMV appears to be able to use copies of eIF(iso)4E at two loci. Transformation of different copies of eIF(iso)4E from a resistant B. rapa line into an eIF(iso)4E knockout line of Arabidopsis thaliana proved misleading because it showed that, when expressed ectopically, TuMV could use multiple copies which was not the case in the resistant B. rapa line. The inability of TuMV to access multiple copies of eIF(iso)4E in B. rapa and the broad spectrum of the resistance suggest it may be durable.
authors.affiliation: School of Life Sciences, University of Warwick, Wellesbourne, Warwick, CV35 9EF, UK.
authors.forename: Charlotte F
authors.initials: CF
authors.lastname: Nellist
authors.forename: Wei
authors.initials: W
authors.lastname: Qian
authors.forename: Carol E
authors.initials: CE
authors.lastname: Jenner
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Moore
authors.forename: Shujiang
authors.initials: S
authors.lastname: Zhang
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Wang
authors.forename: William H
authors.initials: WH
authors.lastname: Briggs
authors.forename: Guy C
authors.initials: GC
authors.lastname: Barker
authors.forename: Rifei
authors.initials: R
authors.lastname: Sun
authors.forename: John A
authors.initials: JA
authors.lastname: Walsh
mesh_terms: D029741:Brassica rapa / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D018388:Codon, Terminator; D039642:Eukaryotic Initiation Factors / Q000378:metabolism*; D017343:Genes, Plant; D005808:Genes, Recessive; D007438:Introns; D008969:Molecular Sequence Data; D012326:RNA Splicing
chemical_list: D018388:Codon, Terminator; D039642:Eukaryotic Initiation Factors
keywords: Arabidopsis thaliana; Brassica rapa; Chinese cabbage; Turnip mosaic virus; broad-spectrum virus resistance; eIF(iso)4E; mis-splicing