Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

International audienceThe moth Spodoptera frugiperda is a well-known pest of crops throughout the Americas, which consists of two strains adapted to different host-plants: the first feeds preferentially on corn, cotton and sorghum whereas the second is more associated with rice and several pasture grasses. Though morphologically indistinguishable, they exhibit differences in their mating behavior, pheromone compositions, and show development variability according to the host-plant. Though the latter suggest that both strains are different species, this issue is still highly controversial because hybrids naturally occur in the wild, not to mention the discrepancies among published results concerning mating success between the two strains. In order to clarify the status of the two host-plant strains of S. frugiperda, we analyze features that possibly reflect the level of post-zygotic isolation: (1) first generation (F1) hybrid lethality and sterility; (2) patterns of meiotic segregation of hybrids in reciprocal second generation (F2), as compared to the meiosis of the two parental strains. We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny. Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field. Altogether these results provide additional evidence in favor of a sibling species status for the two strains

Rôle des Glutathion-S-transférases fongiques dans la protection contre les métabolites de défenses des Brassicacées

National audienc

Rôle des Glutathion-S-transférases fongiques dans la protection contre les métabolites de défenses des Brassicacées

National audienc

New developments in KisSplice: Combining local and global transcriptome assemblers to decipher splicing in RNA-seq data

International audienc

New developments in KisSplice: Combining local and global transcriptome assemblers to decipher splicing in RNA-seq data

International audienc

Class 1 integrons in Acinetobacter baumannii: a weak expression of gene cassettes to counterbalance the lack of LexA-driven integrase repression

International audienceIntegrons are able to recruit resistance genes through integrase-driven recombination events that are regulated by the bacterial SOS response and require the repressor LexA. Class 1 integrons genes are expressed from a common promoter, Pc, of which at least 5 predominant variants, classified from weak to strong, have been described. In Escherichia coli, there is an intertwined regulation between gene cassette expression and integrase activity: the stronger the promoter is, the weaker the integrase is. Class 1 integrons have been frequently described in Acinetobacter baumannii. However, Acinetobacter spp. lack the LexA repressor suggesting that the integrase is constitutively expressed. We characterized the integron content of 83 clinical and environmental A. baumannii strains. We found a predominance of Pc variants described as strong in E. coli. The Pc expression level was 2 to 4-fold lower in A. baumannii than in E. coli, and the diversity of the gene cassette array was low. In A.baumannii integrons with a PcS promoter might have been selected to allow a sufficient resistance level while avoiding the toxicity of a highly active integrase. Furthermore, a transcriptional interference between PcS and PintI1 (as shown in E.coli) may limit the expression of the integrase and thus counterbalance the lack of LexA-driven integrase repression to prevent the cost of the integrase

Class 1 integrons in Acinetobacter baumannii: a weak expression of gene cassettes to counterbalance the lack of LexA-driven integrase repression

International audienceIntegrons are able to recruit resistance genes through integrase-driven recombination events that are regulated by the bacterial SOS response and require the repressor LexA. Class 1 integrons genes are expressed from a common promoter, Pc, of which at least 5 predominant variants, classified from weak to strong, have been described. In Escherichia coli, there is an intertwined regulation between gene cassette expression and integrase activity: the stronger the promoter is, the weaker the integrase is. Class 1 integrons have been frequently described in Acinetobacter baumannii. However, Acinetobacter spp. lack the LexA repressor suggesting that the integrase is constitutively expressed. We characterized the integron content of 83 clinical and environmental A. baumannii strains. We found a predominance of Pc variants described as strong in E. coli. The Pc expression level was 2 to 4-fold lower in A. baumannii than in E. coli, and the diversity of the gene cassette array was low. In A.baumannii integrons with a PcS promoter might have been selected to allow a sufficient resistance level while avoiding the toxicity of a highly active integrase. Furthermore, a transcriptional interference between PcS and PintI1 (as shown in E.coli) may limit the expression of the integrase and thus counterbalance the lack of LexA-driven integrase repression to prevent the cost of the integrase

Viral metagenomics analysis of kidney donors and recipients: Torque teno virus genotyping and prevalence

International audienceAbstract The viral load of the ubiquitous and nonpathogenic torque teno virus (TTV) is associated with the grade of immunosuppression of its host. The development of next‐generation sequencing (NGS) allowed to describe the human virome of the blood compartment in transplanted patients, and showed that TTV is the most important part of the virome. This study is a descriptive retrospective pilot study of sequencing plasma samples from 15 matched donors and recipients. After sample processing, nucleic acids were amplified by rolling circle amplification and submitted to NGS by ion proton sequencing technology. Results were analyzed after mapping of reads on the 29 TTV reference genomes and de novo assembling of the reads with MIRA software. The number of TTV species present in donors and recipients was, on average, 12 in donors and 33 in recipients. TTV species predominantly present in donors were TTV‐13 and TTV‐18; and in recipients were TTV‐P15‐2, TTV‐27, TTV‐HD14a, and TTV‐22. We highlighted a significant variability in abundance and composition in sequential samples from recipients. Temporal evolution of TTV populations was clearly observed in recipients, but no preferential transmission of a species from donor to recipient was evidenced. Diversity and population expansion were observed in kidney recipients. Further study of TTV species could help assess the potential impact of each species of this virus