Historical Contingencies Modulate the Adaptability of Rice Yellow Mottle Virus

The rymv1-2 and rymv1-3 alleles of the RYMV1 resistance to Rice yellow mottle virus (RYMV), coded by an eIF(iso)4G1 gene, occur in a few cultivars of the Asiatic (Oryza sativa) and African (O. glaberrima) rice species, respectively. The most salient feature of the resistance breaking (RB) process is the converse genetic barrier to rymv1-2 and rymv1-3 resistance breakdown. This specificity is modulated by the amino acid (glutamic acid vs. threonine) at codon 49 of the Viral Protein genome-linked (VPg), a position which is adjacent to the virulence codons 48 and 52. Isolates with a glutamic acid (E) do not overcome rymv1-3 whereas those with a threonine (T) rarely overcome rymv1-2. We found that isolates with T49 had a strong selective advantage over isolates with E49 in O. glaberrima susceptible cultivars. This explains the fixation of the mutation T49 during RYMV evolution and accounts for the diversifying selection estimated at codon 49. Better adapted to O. glaberrima, isolates with T49 are also more prone than isolates with E49 to fix rymv1-3 RB mutations at codon 52 in resistant O. glaberrima cultivars. However, subsequent genetic constraints impaired the ability of isolates with T49 to fix rymv1-2 RB mutations at codons 48 and 52 in resistant O. sativa cultivars. The origin and role of the amino acid at codon 49 of the VPg exemplifies the importance of historical contingencies in the ability of RYMV to overcome RYMV1 resistance

CNS Delivery Via Adsorptive Transcytosis

Adsorptive-mediated transcytosis (AMT) provides a means for brain delivery of medicines across the blood-brain barrier (BBB). The BBB is readily equipped for the AMT process: it provides both the potential for binding and uptake of cationic molecules to the luminal surface of endothelial cells, and then for exocytosis at the abluminal surface. The transcytotic pathways present at the BBB and its morphological and enzymatic properties provide the means for movement of the molecules through the endothelial cytoplasm. AMT-based drug delivery to the brain was performed using cationic proteins and cell-penetrating peptides (CPPs). Protein cationization using either synthetic or natural polyamines is discussed and some examples of diamine/polyamine modified proteins that cross BBB are described. Two main families of CPPs belonging to the Tat-derived peptides and Syn-B vectors have been extensively used in CPP vector-mediated strategies allowing delivery of a large variety of small molecules as well as proteins across cell membranes in vitro and the BBB in vivo. CPP strategy suffers from several limitations such as toxicity and immunogenicity—like the cationization strategy—as well as the instability of peptide vectors in biological media. The review concludes by stressing the need to improve the understanding of AMT mechanisms at BBB and the effectiveness of cationized proteins and CPP-vectorized proteins as neurotherapeutics

Carbon‐13 magnetic resonance study of spiro compounds

A large series of cyclohexane and cyclopentane spiro compounds has been studied by carbon‐13 NMR. Increments have been derived in terms of α, β, γ spiro substituent effects, one ring being considered as the substituent of the other. As usual α and β effects are paramagnetic and γ effects are diamagnetic. They are compared with the corresponding effects associated with the introduction of a gem dimethyl group into a cyclohexane or cyclopentane ring. The size of the two rings involved in the spirane structure has a marked influence especially on the chemical shift of the spirane carbon atom. Comparison between monospiro and dispiro derivatives gives information about the so‐called 1,5 or δ effect which is paramagnetic. From an analytical point of view, carbon‐13 NMR appears to be a powerful method of detecting the spirane structure, apparently including the relative size of the rings. Copyright © 1974 Heyden & Son Ltd.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Gene expression in mesophyll protoplasts

International audienc

Rice yellow mottle virus is a suitable amplicon vector for an efficient production of an anti-leishmianiasis vaccine in Nicotiana benthamiana leaves

International audienceBackground Since the 2000's, plants have been used as bioreactors for the transient production of molecules of interest such as vaccines. To improve protein yield, "amplicon" vectors based on plant viruses are used. These viral constructs, engineered to carry the gene of interest replicate strongly once introduced into the plant cell, allowing significant accumulation of the protein. Here, we evaluated the suitability of the monocot-infecting RNA virus Rice yellow mottle virus (RYMV) as an amplicon vector. The promastigote surface antigen (PSA) of the protozoan Leishmania was considered as a protein of interest due to its vaccine properties against canine leishmaniasis. Results Since P1 (ORF1) and CP (ORF3) proteins are not strictly necessary for viral replication, ORF1 was deleted and the PSA gene was substituted to ORF3 in the RYMV-based vector. We evaluated its expression in the best described plant bioreactor system, Nicotiana benthamiana which, unlike rice, allows transient transformation by Agrobacterium. Despite not being its natural host, we demonstrated a low level of RYMV-based vector replication in N. benthamiana leaves. Under optimized ratio, we showed that the P19 silencing suppressor in combination with the missing viral CP ORF significantly enhanced RYMV amplicon replication in N. benthamiana. Under these optimized CP/P19 conditions, we showed that the RYMV amplicon replicated autonomously in the infiltrated N. benthamiana cells, but was unable to move out of the infiltrated zones. Finally, we showed that when the RYMV amplicon was expressed under the optimized conditions we set up, it allowed enhanced PSA protein accumulation in N. benthamiana compared to the PSA coding sequence driven by the 35S promoter without amplicon background. Conclusion This work demonstrates that a non-dicot-infecting virus can be used as an amplicon vector for the efficient production of proteins of interest such as PSA in N. benthamiana leaves

Effects of sweet potato feathery mottle virus, sweet potato chlorotic stunt virus and their co-infection on sweet potato yield in Western Burkina Faso

To determine the effects of sweet potato feathery mottle virus (SPFMV), Sweet potato chlorotic stunt virus (SPCSV) and their co-infection on sweet potato yield, twelve sweet potato varieties were assessed in a hotspot area in Western Burkina Faso. The experiment was carried out in a randomized complete-block design with the twelve varieties in three replications. Data were collected on plant growth parameters, plant virus symptoms and yield parameters. Additional testing for selected sweet potato viruses was done using a nitrocellulose membrane enzyme-linked immunosorbent assay (NCM-ELISA) and RT-PCR. SPFMV and SPCSV were the viruses detected in this study. Varieties Djakani and Ligri were virus-free and had the highest average yields out of twelve sweet potato varieties assessed. Field monitoring indicated that 58% of plants were found to be virus-infected. The results suggest that severe symptoms were associated with sweet potato virus disease (SPVD) and yield reduction. However, the interaction of SPCSV with other viruses, which may result in synergistic negative effects on sweet potato yield and quality, needs further research

Virus-based pharmaceutical production in plants : an opportunity to reduce health problems in Africa

Background Developing African countries face health problems that they struggle to solve. The major causes of this situation are high therapeutic and logistical costs. Plant-made therapeutics are easy to produce due to the lack of the safety considerations associated with traditional fermenter-based expression platforms, such as mammalian cells. Plant biosystems are easy to scale up and inexpensive, and they do not require refrigeration or a sophisticated medical infrastructure. These advantages provide an opportunity for plant-made pharmaceuticals to counteract diseases for which medicines were previously inaccessible to people in countries with few resources. Main body The techniques needed for plant-based therapeutic production are currently available. Viral expression vectors based on plant viruses have greatly enhanced plant-made therapeutic production and have been exploited to produce a variety of proteins of industrial, pharmaceutical and agribusiness interest. Some neglected tropical diseases occurring exclusively in the developing world have found solutions through plant bioreactor technology. Plant viral expression vectors have been reported in the production of therapeutics against these diseases occurring exclusively in the third world, and some virus-derived antigens produced in plants exhibit appropriate antigenicity and immunogenicity. However, all advances in the use of plants as bioreactors have been made by companies in Europe and America. The developing world is still far from acquiring this technology, although plant viral expression vectors may provide crucial help to overcome neglected diseases. Conclusion Today, interest in these tools is rising, and viral amplicons made in and for Africa are in progress. This review describes the biotechnological advances in the field of plant bioreactors, highlights factors restricting access to this technology by those who need it most and proposes a solution to overcome these limitations

Effects of sweet potato feathery mottle virus, sweet potato chlorotic stunt virus and their co-infection on sweet potato yield in Western Burkina Faso

To determine the effects of sweet potato feathery mottle virus (SPFMV), Sweet potato chlorotic stunt virus (SPCSV) and their co-infection on sweet potato yield, twelve sweet potato varieties were assessed in a hotspot area in Western Burkina Faso. The experiment was carried out in a randomized complete-block design with the twelve varieties in three replications. Data were collected on plant growth parameters, plant virus symptoms and yield parameters. Additional testing for selected sweet potato viruses was done using a nitrocellulose membrane enzyme-linked immunosorbent assay (NCM-ELISA) and RT-PCR. SPFMV and SPCSV were the viruses detected in this study. Varieties Djakani and Ligri were virus-free and had the highest average yields out of twelve sweet potato varieties assessed. Field monitoring indicated that 58% of plants were found to be virus-infected. The results suggest that severe symptoms were associated with sweet potato virus disease (SPVD) and yield reduction. However, the interaction of SPCSV with other viruses, which may result in synergistic negative effects on sweet potato yield and quality, needs further research