Knock-out mutation of eukaryotic initiation factor 4E2 (eIF4E2) confers resistance to pepper veinal mottle virus in tomato.

Translation initiation factors 4E (eIF4E) are the main source of resistance to potyvirus. We systematically assessed tomato single and double knock-out (KO) mutants of members of the eIF4E-coding gene family for resistance to Pepper veinal mottle virus (PVMV), a major constraint to tomato production. We show that the KO mutant of eIF4E2 has partial resistance to PVMV isolate IC, with plants harboring weak symptoms and low virus loads at the systemic level. The causal effect of eIF4E2 loss-of-function on resistance was confirmed on a progeny segregating for the KO mutation. The eIF4E2 KO mutant was resistant to six of the eight PVMV isolates tested and no resistance to other potyviruses was observed. This is the first evidence that mutation of eIF4E2 is in itself conferring resistance to a potyvirus and 3D protein modelling suggests that the eIF4E2 gene could be converted into a functional resistance allele.

A new eIF4E1 allele characterized by RNAseq data mining is associated with resistance to potato virus Y in tomato albeit with a low durability.

Allele mining on susceptibility factors offers opportunities to find new sources of resistance among crop wild relatives for breeding purposes. As a proof of concept, we used available RNAseq data to investigate polymorphisms among the four tomato genes encoding translation initiation factors [eIF4E1 and eIF4E2, eIFiso4E and the related gene new cap-binding protein(nCBP)] to look for new potential resistance alleles to potyviruses. By analysing polymorphism among RNAseq data obtained for 20 tomato accessions, 10 belonging to the cultivated type Solanum lycopersicum and 10 belonging to the closest related wild species Solanum pimpinellifolium, we isolated one new eIF4E1 allele, in the S. pimpinellifolium LA0411 accession, which encodes a potential new resistance allele, mainly due to a polymorphism associated with an amino acid change within eIF4E1 region II. We confirmed that this new allele, pot12, is indeed associated with resistance to potato virus Y, although with a restricted resistance spectrum and a very low durability potential. This suggests that mutations occurring in eIF4E region II only may not be sufficient to provide efficient and durable resistance in plants. However, our study emphasizes the opportunity brought by RNAseq data to mine for new resistance alleles. Moreover, this approach could be extended to seek for putative new resistance alleles by screening for variant forms of susceptibility genes encoding plant host proteins known to interact with viral proteins.

A TILLING approach to generate broad-spectrum resistance to potyviruses in tomato is hampered by eIF4E gene redundancy.

Genetic resistance to pathogens is important for sustainable maintenance of crop yields. Recent biotechnologies offer alternative approaches to generate resistant plants by compensating for the lack of natural resistance. Tomato (Solanum lycopersicum) and related species offer a model in which natural and TILLING-induced potyvirus resistance alleles may be compared. For resistance based on translation initiation factor eIF4E1, we confirm that the natural allele Sh-eIF4E1(PI24)-pot1, isolated from the wild tomato species Solanum habrochaites, is associated with a wide spectrum of resistance to both potato virus Y and tobacco etch virus isolates. In contrast, a null allele of the same gene, isolated through a TILLING strategy in cultivated tomato S. lycopersicum, is associated with a much narrower resistance spectrum. Introgressing the null allele into S. habrochaites did not extend its resistance spectrum, indicating that the genetic background is not responsible for the broad resistance. Instead, the different types of eIF4E1 mutations affect the levels of eIF4E2 differently, suggesting that eIF4E2 is also involved in potyvirus resistance. Indeed, combining two null mutations affecting eIF4E1 and eIF4E2 re-establishes a wide resistance spectrum in cultivated tomato, but to the detriment of plant development. These results highlight redundancy effects within the eIF4E gene family, where regulation of expression alters susceptibility or resistance to potyviruses. For crop improvement, using loss-of-function alleles to generate resistance may be counter-productive if they narrow the resistance spectrum and limit growth. It may be more effective to use alleles encoding functional variants similar to those found in natural diversity.

Nanoparticles functionalised with an anti-platelet human antibody for in vivo detection of atherosclerotic plaque by magnetic resonance imaging.

Atherosclerosis is an inflammatory disease associated with the formation of atheroma plaques likely to rupture in which platelets are involved both in atherogenesis and atherothrombosis. The rupture is linked to the molecular composition of vulnerable plaques, causing acute cardiovascular events. In this study we propose an original targeted contrast agent for molecular imaging of atherosclerosis. Versatile USPIO (VUSPIO) nanoparticles, enhancing contrast in MR imaging, were functionalised with a recombinant human IgG4 antibody, rIgG4 TEG4, targeting human activated platelets. The maintenance of immunoreactivity of the targeted VUSPIO against platelets was confirmed in vitro by flow cytometry, transmission electronic and optical microscopy. In the atherosclerotic ApoE(-/-) mouse model, high-resolution ex vivo MRI demonstrated the selective binding of TEG4-VUSPIO on atheroma plaques. It is noteworthy that the rationale for targeting platelets within atherosclerotic lesions is highlighted by our targeted contrast agent using a human anti-αIIbß3 antibody as a targeting moiety. FROM THE CLINICAL EDITOR: Current clinical assessment of atherosclerotic plagues is suboptimal. The authors in the article designed functionalized superparamagnetic iron oxide nanoparticles with TEG4, a recombinant human antibody, to target activated platelets. By using MRI, these nanoparticles can be utilized to study the process of atheroma pathogenesis.