Cell wall chitosaccharides are essential components and exposed patterns of the phytopathogenic oomycete Aphanomyces euteiches.
Chitin is an essential component of fungal cell walls, where it forms a crystalline scaffold, and chitooligosaccharides derived from it are signaling molecules recognized by the hosts of pathogenic fungi. Oomycetes are cellulosic fungus-like microorganisms which most often lack chitin in their cell walls. Here we present the first study of the cell wall of the oomycete Aphanomyces euteiches, a major parasite of legume plants. Biochemical analyses demonstrated the presence of ca. 10% N-acetyl-D-glucosamine (GlcNAc) in the cell wall. Further characterization of the GlcNAc-containing material revealed that it corresponds to noncrystalline chitosaccharides associated with glucans, rather than to chitin per se. Two putative chitin synthase (CHS) genes were identified by data mining of an A. euteiches expressed sequence tag collection and Southern blot analysis, and full-length cDNA sequences of both genes were obtained. Phylogeny analysis indicated that oomycete CHS diversification occurred before the divergence of the major oomycete lineages. Remarkably, lectin labeling showed that the Aphanomyces euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function. These data open new perspectives for the development of antioomycete drugs and further studies of the molecular mechanisms involved in the recognition of pathogenic oomycetes by the host plants.
Badreddine
Ilham
I
UMR 5546, CNRS-Université Paul-Sabatier, 24 Chemin de Borde-Rouge, BP 42617, Auzeville, F-31326 Castanet-Tolosan, France.
Lafitte
Claude
C
Heux
Laurent
L
Skandalis
Nicholas
N
Spanou
Zacharoula
Z
Martinez
Yves
Y
Esquerré-Tugayé
Marie-Thérèse
MT
Bulone
Vincent
V
Dumas
Bernard
B
Bottin
Arnaud
A
D000595:Amino Acid Sequence; D044744:Aphanomyces / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism*; D002687:Chitin Synthase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D048271:Chitosan / Q000378:metabolism*; D007887:Fabaceae / Q000382:microbiology*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D016415:Sequence Alignment
D005656:Fungal Proteins; D048271:Chitosan; D002687:Chitin Synthase