title: Genome-wide analyses of chitin synthases identify horizontal gene transfers towards bacteria and allow a robust and unifying classification into fungi.
abstract: Chitin, the second most abundant biopolymer on earth after cellulose, is found in probably all fungi, many animals (mainly invertebrates), several protists and a few algae, playing an essential role in the development of many of them. This polysaccharide is produced by type 2 glycosyltransferases, called chitin synthases (CHS). There are several contradictory classifications of CHS isoenzymes and, as regards their evolutionary history, their origin and diversity is still a matter of debate.
  
  
  
  A genome-wide analysis resulted in the detection of more than eight hundred putative chitin synthases in proteomes associated with about 130 genomes. Phylogenetic analyses were performed with special care to avoid any pitfalls associated with the peculiarities of these sequences (e.g. highly variable regions, truncated or recombined sequences, long-branch attraction). This allowed us to revise and unify the fungal CHS classification and to study the evolutionary history of the CHS multigenic family. This update has the advantage of being user-friendly due to the development of a dedicated website ( http://wwwabi.snv.jussieu.fr/public/CHSdb ), and it includes any correspondences with previously published classifications and mutants. Concerning the evolutionary history of CHS, this family has mainly evolved via duplications and losses. However, it is likely that several horizontal gene transfers (HGT) also occurred in eukaryotic microorganisms and, even more surprisingly, in bacteria.
  
  
  
  This comprehensive multi-species analysis contributes to the classification of fungal CHS, in particular by optimizing its robustness, consensuality and accessibility. It also highlights the importance of HGT in the evolutionary history of CHS and describes bacterial chs genes for the first time. Many of the bacteria that have acquired a chitin synthase are plant pathogens (e.g. Dickeya spp; Pectobacterium spp; Brenneria spp; Agrobacterium vitis and Pseudomonas cichorii). Whether they are able to produce a chitin exopolysaccharide or secrete chitooligosaccharides requires further investigation.
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Microbiologie Adaptation et Pathogénie, Bâtiment André Lwoff, 10 rue Raphaël Dubois, F-69622, Villeurbanne, France. isabelle.goncalves@univ-lyon1.fr.|BAYER S.A.S., Centre de Recherche de la Dargoire, F-69263, Lyon, France. isabelle.goncalves@univ-lyon1.fr.
authors.forename: Isabelle R
authors.initials: IR
authors.lastname: Gonçalves
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7205 (MNHN, UPMC, CNRS, EPHE), Atelier de Bioinformatique, F-75231, Paris, Cedex 05, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Brouillet
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INRA-AgroParisTech UMR1318, F-78026, Versailles, France.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Soulié
authors.affiliation: Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, Département de Microbiologie, 25 rue du Docteur Roux, F-75015, Paris, France.
authors.forename: Simonetta
authors.initials: S
authors.lastname: Gribaldo
authors.affiliation: BAYER S.A.S., Centre de Recherche de la Dargoire, F-69263, Lyon, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Sirven
authors.affiliation: BAYER S.A.S., Centre de Recherche de la Dargoire, F-69263, Lyon, France.
authors.forename: Noémie
authors.initials: N
authors.lastname: Charron
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7205 (MNHN, UPMC, CNRS, EPHE), Atelier de Bioinformatique, F-75231, Paris, Cedex 05, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Boccara
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Microbiologie Adaptation et Pathogénie, Bâtiment André Lwoff, 10 rue Raphaël Dubois, F-69622, Villeurbanne, France.|BAYER S.A.S., Centre de Recherche de la Dargoire, F-69263, Lyon, France.
authors.forename: Mathias
authors.initials: M
authors.lastname: Choquer
mesh_terms: D000818:Animals; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D002687:Chitin Synthase / Q000145:classification* / Q000235:genetics* / Q000378:metabolism; D056890:Eukaryota / Q000201:enzymology; D019143:Evolution, Molecular; D005658:Fungi / Q000201:enzymology* / Q000235:genetics; D022761:Gene Transfer, Horizontal; D016680:Genome, Bacterial; D055106:Genome-Wide Association Study; D005810:Multigene Family; D010802:Phylogeny; D011995:Recombination, Genetic / Q000235:genetics; D014780:Viruses / Q000201:enzymology
chemical_list: D002687:Chitin Synthase
keywords: Bacteria; Chitin synthase; Classification; Evolution; Fungi; Horizontal gene transfer