Biology subjects

Desbiez, C.

Publications and source records attributed to Desbiez, C..

3 recordsLinked to original sources

bioRxiv2026

Common molecular determinants underlie potyvirus host species jumps and resistance breakdown.

Given their rapid evolutionary dynamics, viruses offer a powerful system to investigate the mechanisms underlying host jumps. Here, we experimentally evolved endive necrotic mosaic virus (ENMV) in five plant hosts within the family Asteraceae: two putative ancestral hosts (Lactuca sativa and Tragopogon pratensis), and three alternative crop or weed species (Cichorium endivia, Zinnia elegans and Calendula arvensis). The resulting evolved viral populations, together with the ancestral strain, were then evaluated in a reciprocal cross-inoculation experiment across all five host species. ENMV exhibited clear adaptive responses in two hosts, Z. elegans and C. arvensis, with increased infection success and higher systemic viral accumulation compared to the ancestral virus. In contrast, no evidence of adaptation was detected in L. sativa, T. pratensis and C. endivia. Strikingly, strong cross-adaptation emerged between Z. elegans and C. arvensis: viral populations evolved in either host consistently outperformed those evolved in other hosts, as well as the ancestral strain, when infecting the reciprocal host. Sequencing of the VPg cistron in adapted populations revealed multiple nonsynonymous mutations, several of which arose independently across evolutionary lineages and in both Z. elegans and C. arvensis selection regimes. Functional assays using an infectious ENMV cDNA clone demonstrated that seven of these substitutions, individually or in combination, significantly increased the infection rate in both Z. elegans and C. arvensis. Notably, several of these substitutions also enhanced infectivity across four additional Asteraceae species among the eleven tested, without a clear relationship to host phylogenetic distance. Remarkably, all identified substitutions map to amino acid positions or adjacent residues in VPg previously implicated in the breakdown of recessive resistance genes against potyviruses in both crop and model plant systems. Together, these results suggest that adaptation to host resistance and host range expansion in potyviruses may rely, at least in part, on shared molecular pathways.

evolutionary biology↗

bioRxiv2024

Reconceptualizing programmed transcriptional slippage in RNA viruses

RNA viruses have evolved sophisticated strategies to exploit the limited encoded information within their typically compact genomes. One of such, named programmed transcriptional slippage (PTS), is defined by the insertion of an additional A at An motifs (n [≥] 6) of newly synthetized viral transcripts to get access to overlapping open reading frames (ORFs). Although key proteins from Ebolavirus and potyvirids (members of the Potyviridae family) are expressed via PTS, available information about this phenomenon is very scarce. Here, by using diverse experimental approaches and a collection of plant/virus combinations, we discover cases in which PTS does not fit with its current definition. In summary, we observe (i) high rate of single nucleotide deletions at slippage motifs, (ii) overlapping ORFs acceded by slippage at an U8 stretch, and (iii) significant changes in slippage rates induced by factors not related to cognate viruses. Moreover, a survey of full-genome sequences from potyvirids shows a widespread occurrence of species-specific An/Un (n [≥] 6) motifs. Even though many of them, but not all, lead to the production of truncated proteins rather than access to overlapping ORFs, these results suggest that slippage motifs appear more frequently than expected and play relevant roles during virus evolution. In conclusion, our data prompt to broaden PTS definition in RNA viruses. Considering the potential of this phenomenon to expand the viral proteome by acceding to overlapping ORFs and/or producing truncated proteins, a revaluation of PTS significance during infections of RNA viruses is required. IMPORTANCEProgrammed transcriptional slippage (PTS) is used by RNA viruses as another strategy to maximise the coding information in their genomes. This phenomenon is based on a peculiar feature of viral replicases: they insert an untemplated A in An motifs (n [≥] 6) in a small fraction of newly synthesised viral RNAs. As a consequence, ribosomes can get access to overlapping open reading frames (ORFs) when translating those particular transcripts. Here, using plant-infecting RNA viruses as models, we discover cases challenging the previously stablished definition of viral PTS, prompting us to reconsider and redefine this expression strategy. An interesting conclusion from our study is that PTS might be more relevant during RNA virus evolution and infection processes than previously assumed.

molecular biology↗

bioRxiv2020

Emerging strains of watermelon mosaic virus in Southeastern France: model-based estimation of the dates and places of introduction

Where and when alien organisms are successfully introduced are central questions to elucidate biotic and abiotic conditions favorable to the introduction, establishment and spread of invasive species. We propose a modelling framework to analyze multiple introductions by several invasive genotypes or genetic variants, in competition with a resident population, when observations provide knowledge on the relative proportions of each variant at some dates and places. This framework is based on a mechanistic-statistical model coupling a reaction-diffusion model with a probabilistic observation model. We apply it to a spatio-temporal dataset reporting the relative proportions of five genetic variants of watermelon mosaic virus (WMV, genus Potyvirus, family Potyviridae) in infections of commercial cucurbit fields. Despite the parsimonious nature of the model, it succeeds in fitting the data well and provides an estimation of the dates and places of successful introduction of each emerging variant as well as a reconstruction of the dynamics of each variant since its introduction.

ecology↗