Knock-Down of Both eIF4E1 and eIF4E2 Genes Confers Broad-Spectrum Resistance against Potyviruses in Tomato

Background: The eukaryotic translation initiation factor eIF4E plays a key role in plant-potyvirus interactions. eIF4E belongs to a small multigenic family and three genes, eIF4E1, eIF4E2 and eIF(iso)4E, have been identified in tomato. It has been demonstrated that eIF4E-mediated natural recessive resistances against potyviruses result from non-synonymous mutations in an eIF4E protein, which impair its direct interaction with the potyviral protein VPg. In tomato, the role of eIF4E proteins in potyvirus resistance is still unclear because natural or induced mutations in eIF4E1 confer only a narrow resistance spectrum against potyviruses. This contrasts with the broad spectrum resistance identified in the natural diversity of tomato. These results suggest that more than one eIF4E protein form is involved in the observed broad spectrum resistance Methodology/Principal Findings: To gain insight into the respective contribution of each eIF4E protein in tomato-potyvirus interactions, two tomato lines silenced for both eIF4E1 and eIF4E2 (RNAi-4E) and two lines silenced for eIF(iso)4E (RNAi-iso4E) were obtained and characterized. RNAi-4E lines are slightly impaired in their growth and fertility, whereas no obvious growth defects were observed in RNAi-iso4E lines. The F1 hybrid between RNAi-4E and RNAi-iso4E lines presented a pronounced semi-dwarf phenotype. Interestingly, the RNAi-4E lines silenced for both eIF4E1 and eIF4E2 showed broad spectrum resistance to potyviruses while the RNAi-iso4E lines were fully susceptible to potyviruses. Yeast two-hybrid interaction assays between the three eIF4E proteins and a set of viral VPgs identified two types of VPgs: those that interacted only with eIF4E1 and those that interacted with either eIF4E1 or with eIF4E2 Conclusion/Significance: These experiments provide evidence for the involvement of both eIF4E1 and eIF4E2 in broad spectrum resistance of tomato against potyviruses and suggest a role for eIF4E2 in tomato-potyvirus interactions

Development and evaluation of robust molecular markers linked to disease resistance in tomato for distinctness, uniformity and stability testing

Molecular markers linked to phenotypically important traits are of great interest especially when traits are difficult and/or costly to be observed. In tomato where a strong focus on resistance breeding has led to the introgression of several resistance genes, resistance traits have become important characteristics in distinctness, uniformity and stability (DUS) testing for Plant Breeders Rights (PBR) applications. Evaluation of disease traits in biological assays is not always straightforward because assays are often influenced by environmental factors, and difficulties in scoring exist. In this study, we describe the development and/or evaluation of molecular marker assays for the Verticillium genes Ve1 and Ve2, the tomato mosaic virusTm1 (linked marker), the tomato mosaic virus Tm2 and Tm22 genes, the Meloidogyne incognita Mi1-2 gene, the Fusarium I (linked marker) and I2 loci, which are obligatory traits in PBR testing. The marker assays were evaluated for their robustness in a ring test and then evaluated in a set of varieties. Although in general, results between biological assays and marker assays gave highly correlated results, marker assays showed an advantage over biological tests in that the results were clearer, i.e., homozygote/heterozygote presence of the resistance gene can be detected and heterogeneity in seed lots can be identified readily. Within the UPOV framework for granting of PBR, the markers have the potential to fulfil the requirements needed for implementation in DUS testing of candidate varieties and could complement or may be an alternative to the pathogenesis tests that are carried out at present

An Induced Mutation in Tomato eIF4E Leads to Immunity to Two Potyviruses

BACKGROUND: The characterization of natural recessive resistance genes and Arabidopsis virus-resistant mutants have implicated translation initiation factors of the eIF4E and eIF4G families as susceptibility factors required for virus infection and resistance function. METHODOLOGY/PRINCIPAL FINDINGS: To investigate further the role of translation initiation factors in virus resistance we set up a TILLING platform in tomato, cloned genes encoding for translation initiation factors eIF4E and eIF4G and screened for induced mutations that lead to virus resistance. A splicing mutant of the eukaryotic translation initiation factor, S.l_eIF4E1 G1485A, was identified and characterized with respect to cap binding activity and resistance spectrum. Molecular analysis of the transcript of the mutant form showed that both the second and the third exons were miss-spliced, leading to a truncated mRNA. The resulting truncated eIF4E1 protein is also impaired in cap-binding activity. The mutant line had no growth defect, likely because of functional redundancy with others eIF4E isoforms. When infected with different potyviruses, the mutant line was immune to two strains of Potato virus Y and Pepper mottle virus and susceptible to Tobacco each virus. CONCLUSIONS/SIGNIFICANCE: Mutation analysis of translation initiation factors shows that translation initiation factors of the eIF4E family are determinants of plant susceptibility to RNA viruses and viruses have adopted strategies to use different isoforms. This work also demonstrates the effectiveness of TILLING as a reverse genetics tool to improve crop species. We have also developed a complete tool that can be used for both forward and reverse genetics in tomato, for both basic science and crop improvement. By opening it to the community, we hope to fulfill the expectations of both crop breeders and scientists who are using tomato as their model of study

Caractérisation fonctionnelle et évolution moléculaire des gènes codant pour les facteurs d'initiation de la traduction eIF4E (des facteurs clés dans la résistance des plantes aux potyvirus)

L'objectif de cette étude est de décrire puis analyser et comparer le polymorphisme de séquence des gènes eIF4E (eukaryotic Initiation Factor 4E) de résistance aux potyvirus, afin de mettre en relation ce polymorphisme avec la double fonction des protéines eIF4E dans les processus cellulaires de l'hôte et dans l'interaction avec les potyvirus. La stratégie repose sur l'association d'analyses fonctionnelles et d'études d'évolution moléculaire des gènes eIF4E chez deux Solanacées (piment et tomate) et chez l'espèce modèle Arabidopsis thaliana. En ce qui concerne le rôle de eIF4E dans les processus cellulaires, la pression de sélection purificatrice forte identifiée pour l'ensemble des gènes eIF4E argumente en faveur de l'acquisition d'une spécialisation fonctionnelle, et ce bien que toutes les protéines eIF4E apparaissent capables de complémenter une levure délétée de son gène eIF4E. En ce qui concerne le rôle de eIF4E dans les interactions plantes-potyvirus, une importante diversité de variants alléliques a été identifiée au locus eIF4E1-pvr2 du piment, diversité caractérisée par des substitutions nucléotidiques exclusivement non-synonymes. La plupart de ces substitutions, impliquées dans la résistance aux PVY (Potato virus Y) et TEV (Tobacco etch virus) via une modification de l'interaction avec la protéine virale VPg (Viral Protein genomelinked), sont sous pression de sélection positive. Ces résultats couplés à ceux montrant que des mutations dans la VPg permettent aux potyvirus de s'adapter aux protéines eIF4E1 de résistance, mettent en évidence l'existence d'une coévolution entre eIF4E1 et VPg. Cette coévolution n'est cependant pas retrouvée chez la tomate et A. thaliana, indiquant que leurs caractéristiques biologiques d'interaction avec les potyvirus "in natura" conduisent à des profils différents d'évolution des gènes eIF4E. Plus globalement, ces résultats associés à ceux montrant la conservation de la position des substitutions en acides aminés dans les protéines eIF4E de résistance d'espèces très éloignées suggèrent l'existence d'une évolution convergente.AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Translation initiation factors: a weak link in plant RNA virus infection

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Carole Caranta, a smooth strategist

Head of a scientific division that brings together more than 70% of researchers in plant biology and breeding nationwide, Carole Caranta plays a key role in INRA’s research and partnership strategies. Her career is marked by a passion for science, openness to others, striking a balance between fundamental and targeted research, and forging socio-economic partnerships

Procédé de sélection ou d'obtention de plantes résistantes au PVMV

La présente invention est relative à la sélection ou à l'obtention de plantes résistantes au Pepper veinal mottle virus (PVMV) par la détection ou par l'induction d'une combinaison de mutations dans les gènes eIF4E et eIF(iso)4E desdites plantes

Plant resistance to viruses mediated by translation initiation factors

Host resistance to viruses can show dominant or recessive inheritance. Remarkably, recessive resistance genes are much more common for viruses than for other plant pathogens. Recessive resistances to viruses are especially well documented within the dicotyledons, and have been described for various viruses that belong to very different viral genera, although clearly they predominate among viruses belonging to the genus Potyvirus. The elucidation of the molecular nature of this particular class of resistance genes is recent, but has so far only revealed a group of proteins linked to the translation machinery, chiefly the eukaryotic translation initiation factors (eIF) 4E and 4G, which are the subject of this chapter. Thus, we will briefly review how translation initiation is performed in eukaryotes, to then describe the features and mechanisms of eIF4E- and 4G-mediated resistances to potyviruses and viruses belonging to other genera, such as carmoviruses. We will bring the chapter to a close by summarizing conclusions and offering potential research perspectives in this fiel

Recent advances in plant virology

Viruses that infect plants are responsible for reduction in both yield and quality of crops around the world, and are thus of great economic importance. This has provided the impetus for the extensive research into the molecular and cellular biology of these pathogens and into their interaction with their plant hosts and their vectors. However interest in plant viruses extends beyond their ability to damage crops. Many plant viruses, for example tobacco mosaic virus, have been used as model systems to provide basic understanding of how viruses express genes and replicate. Others permitted the elucidation of the processes underlying RNA silencing, now recognised as a core epigenetic mechanism underpinning numerous areas of biology. This book attests to the huge diversity of research in plant molecular virology. Written by world authorities in the field, the book opens with two chapters on the translation and replication of viral RNA. Following chapters cover topics such as viral movement within and between plants, plant responses to viral infection, antiviral control measures, virus evolution, and newly emerging plant viruses. To close there are two chapters on biotechnological applications of plant viruses. Throughout the book the focus is on the most recent, cutting-edge research, making this book essential reading for everyone, from researchers and scholars to students, working with plant viruses