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Trois papiers quasi-consécutifs en Juin:

1.    C. Rispe et al., [Genome sequence of the grape phylloxera: insights into the genome evolution and invasion routes of an iconic pest. BMC Biology (2020)] Ce papier fait l'objet d'un communiqué de presse INRAE et d'une reprise de brève UCBL et a fait l'objet d'un article de revue dans The Economist . Notre contribution a été sur l'analyse genomique des transporteurs moléculaires et surtout des protéines cuticulaires de cet insecte, qui subissent (moisn que les effecteurs, mais plus que d'autres familles multigéniques) un diversification/néofonctionnalisation chez les pucerons "modernes", c'est à dire postérieurs à la divergence avec la lignée des Phylloxeridae.

[authors:Rispe, Claude; Legeai, Fabrice; Nabity, Paul; Fernandez, Rosa; Arora, Arinder K. ; Baa-Puyoulet, Patrice; Banfill, Celeste R. ; Bao, Leticia; Barberà , Miquel; Bouallègue, Maryem; Bretaudeau, Anthony; Brisson, Jennifer A. ; Calevro, Federica; Capy, Pierre; Catrice, Olivier; Chertemps, Thomas; Couture, Carole; Delière, Laurent; Douglas, Angela E. ; Dufault-Thompson, Keith; Escuer, Paula; Feng, Honglin; Forneck, Astrid; Gabaldón, Toni; Guigó, Roderic; Hilliou, Frédérique; Hinojosa-Alvarez, Silvia; Hsiao, Yi-min; Hudaverdian, Sylvie; Jacquin-Joly, Emmanuelle; James, Edward B. ; Johnston, Spencer; Joubard, Benjamin; Le Goff, Gaëlle; Le Trionnaire, Gaël; Librado, Pablo; Liu, Shanlin; Lombaert, Eric; Lu, Hsiao-ling; Maïbèche, Martine; Makni, Mohamed; Marcet-Houben, Marina; Martínez-Torres, David; Meslin, Camille; Montagné, Nicolas; Moran, Nancy A. ; Papura, Daciana; Parisot, Nicolas; Rahbé, Yvan; Ribeiro Lopes, Mélanie; Ripoll-Cladellas, Aida; Robin, Stéphanie; Roques, Céline; Roux, Pascale; Rozas, Julio; Sánchez-Gracia, Alejandro; Sánchez-Herrero, Jose F.; Santesmasses, Didac; Scatoni, Iris; Serre, Rémy-Félix; Tang, Ming; Tian, Wenhua; Umina, Paul A. ; van Munster, Manuella; Vincent-Monégat, Carole; Wemmer, Joshua; Wilson, Alex C. C. ; Zhang, Ying; Zhao, Chaoyang; Zhao, Jing; Zhao, Serena; Zhou, Xin; Delmotte, François; Tagu, Denis

Background: Although native to North America, the invasion of the aphid-like grape phylloxera Daktulosphaira vitifoliae across the globe altered the course of grape cultivation. For the past 150 years, viticulture relied on grafting-resistant North American Vitis species as rootstocks, thereby limiting genetic stocks tolerant to other stressors such as pathogens and climate change. Limited understanding of the insect genetics resulted in successive outbreaks across the globe when rootstocks failed. Here we report the 294-Mb genome of D. vitifoliae as a basic tool to understand host plant manipulation, nutritional endosymbiosis, and enhance global viticulture.
Results: Using a combination of genome, RNA, and population resequencing, we found grape phylloxera showed high duplication rates since its common ancestor with aphids, but similarity in most metabolic genes, despite lacking obligate nutritional symbioses and feeding from parenchyma. Similarly, no enrichment occurred in development genes in relation to viviparity. However, phylloxera evolved > 2700 unique genes that resemble putative effectors and are active during feeding. Population sequencing revealed the global invasion began from the upper Mississippi River in North America, spread to Europe and from there to the rest of the world.
Conclusions: The grape phylloxera genome reveals genetic architecture relative to the evolution of nutritional endosymbiosis, viviparity, and herbivory. The extraordinary expansion in effector genes also suggests novel adaptations to plant feeding and how insects induce complex plant phenotypes, for instance galls. Finally, our understanding of the origin of this invasive species and its genome provide genetics resources to alleviate rootstock bottlenecks restricting the advancement of viticulture.
Keywords: Arthropod genomes, Daktulosphaira vitifoliae, Gene duplications, Host plant interactions, Effectors, Biological invasions

Une actualité du département de Santé des Plantes a également été produite en Septembre 2020.

2.    N. Hugouvieux-Cotte-Pattat, C. Brochier-Armanet, J. P. Flandrois, S. Reverchon, Dickeya poaceiphila sp. nov., a plant-pathogenic bacterium isolated from sugar cane (Saccharum officinarum). Int J Syst Evol Microbiol.. Jul 6 (2020).

Abstract : The genus Dickeya is an important group of plant pathogens that currently comprises 10 recognized species. Although most Dickeya isolates originated from infected cultivated plants, they are also isolated from water. The genomic sequence of the Australian strain NCPPB 569T clearly established its separation from the previously characterized Dickeya species. The average nucleotide identity and digital DNA-DNA hybridization values obtained by comparing strain NCPPB 569T with strains of characterized Dickeya species were lower than 87 and 32 %, respectively, supporting the delineation of a new species. The name Dickeya poaceiphila sp. nov. is proposed for this taxon with the type strain NCPPB 569T (=CFBP 8731T). Two other strains isolated in Australia, CFBP 1537 and CFBP 2040, also belong to this species. Phenotypic and genomic comparisons enabled the identification of traits distinguishing D. poaceiphila isolates from strains of other Dickeya species. to come

3.    M. Salvador-Castell, B. Deme, P. Oger, J. Peters, Lipid Phase Separation Induced by the Apolar Polyisoprenoid Squalane Demonstrates Its Role in Membrane Domain Formation in Archaeal Membranes. Langmuir 10.1021/acs.langmuir.0c00901 (2020).

Archaea synthesize methyl-branched, ether phospholipids, which confer the archaeal membrane exceptional physicochemical properties. A novel membrane organization was proposed recently to explain the thermal and high pressure tolerance of the polyextremophilic archaeon Thermococcus barophilus. According to this theoretical model, apolar molecules could populate the midplane of the bilayer and could alter the physicochemical properties of the membrane, among which is the possibility to form membrane domains. We tested this hypothesis using neutron diffraction on a model archaeal membrane composed of two archaeal diether lipids with phosphocholine and phosphoethanolamine headgroups in the presence of the apolar polyisoprenoid squalane. We show that squalane is inserted in the midplane at a maximal concentration between 5 and 10 mol % and that squalane can modify the lateral organization of the membrane and induces the coexistence of separate phases. The lateral reorganization is temperature- and squalane concentration-dependent and could be due to the release of lipid chain frustration and the induction of a negative curvature in the lipids.