title: SUN proteins belong to a novel family of β-(1,3)-glucan-modifying enzymes involved in fungal morphogenesis.
abstract: BACKGROUND
  SUN proteins are involved in yeast morphogenesis, but their function is unknown.
  
  
  RESULTS
  SUN protein plays a role in the Aspergillus fumigatus morphogenesis. Biochemical properties of recombinant SUN proteins were elucidated.
  
  
  CONCLUSIONS
  Both Candida albicans and Aspergillus fumigatus sun proteins show a β-(1,3)-glucanase activity.
  
  
  CONCLUSIONS
  The mode of action of SUN proteins on β-(1,3)-glucan is unique, new, and original. In yeasts, the family of SUN proteins has been involved in cell wall biogenesis. Here, we report the characterization of SUN proteins in a filamentous fungus, Aspergillus fumigatus. The function of the two A. fumigatus SUN genes was investigated by combining reverse genetics and biochemistry. During conidial swelling and mycelial growth, the expression of AfSUN1 was strongly induced, whereas the expression of AfSUN2 was not detectable. Deletion of AfSUN1 negatively affected hyphal growth and conidiation. A closer examination of the morphological defects revealed swollen hyphae, leaky tips, intrahyphal growth, and double cell wall, suggesting that, like in yeast, AfSun1p is associated with cell wall biogenesis. In contrast to AfSUN1, deletion of AfSUN2 either in the parental strain or in the AfSUN1 single mutant strain did not affect colony and hyphal morphology. Biochemical characterization of the recombinant AfSun1p and Candida albicans Sun41p showed that both proteins had a unique hydrolysis pattern: acting on β-(1,3)-oligomers from dimer up to insoluble β-(1,3)-glucan. Referring to the CAZy database, it is clear that fungal SUN proteins represent a new family of glucan hydrolases (GH132) and play an important morphogenetic role in fungal cell wall biogenesis and septation.
authors.affiliation: Institut Pasteur, Unité des Aspergillus, Département Parasitologie et Mycologie, 25 rue du Docteur Roux, F-75015 Paris.
authors.forename: Amandine
authors.initials: A
authors.lastname: Gastebois
authors.forename: Vishukumar
authors.initials: V
authors.lastname: Aimanianda
authors.forename: Sophie
authors.initials: S
authors.lastname: Bachellier-Bassi
authors.forename: Audrey
authors.initials: A
authors.lastname: Nesseir
authors.forename: Arnaud
authors.initials: A
authors.lastname: Firon
authors.forename: Anne
authors.initials: A
authors.lastname: Beauvais
authors.forename: Christine
authors.initials: C
authors.lastname: Schmitt
authors.forename: Patrick
authors.initials: P
authors.lastname: England
authors.forename: Rémi
authors.initials: R
authors.lastname: Beau
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Prévost
authors.forename: Christophe
authors.initials: C
authors.lastname: d'Enfert
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Latgé
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mouyna
mesh_terms: D000595:Amino Acid Sequence; D001232:Aspergillus fumigatus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D002176:Candida albicans / Q000201:enzymology; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D015966:Gene Expression Regulation, Fungal; D006023:Glycoproteins / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006868:Hydrolysis; D025301:Hyphae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009844:Oligosaccharides / Q000737:chemistry; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid; D013172:Spores, Fungal / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: D005656:Fungal Proteins; D006023:Glycoproteins; D009844:Oligosaccharides; D006026:Glycoside Hydrolases
keywords: Aspergillus; Aspergillus fumigatus; Candida albicans; Carbohydrate-binding Protein; Cell Wall; Glucan Hydrolase Activity; Glycoside Hydrolases; SUN