The Lmgpi15 gene, encoding a component of the glycosylphosphatidylinositol anchor biosynthesis pathway, is required for morphogenesis and pathogenicity in Leptosphaeria maculans.
Random insertional mutagenesis was used to investigate pathogenicity determinants in Leptosphaeria maculans. One tagged nonpathogenic mutant, termed m20, was analysed in detail here. The mutant phenotype was investigated by microscopic analyses of infected plant tissues and in vitro growth assays. Complementation and silencing experiments were used to identify the altered gene. Its function was determined by bioinformatics analyses, cell biology experiments and functional studies. The mutant was blocked at the invasive growth phase after an unaffected initial penetration stage, and displayed a reduced growth rate and an aberrant hyphal morphology in vitro. The T-DNA insertion occurred in the intergenic region between two head-to-tail genes, leading to a complex deregulation of their expression. The unique gene accounting for the mutant phenotype was suggested to be the orthologue of the poorly conserved Saccharomyces cerevisiae gpi15, which encodes for one component of the glycosylphosphatidylinositol (GPI) anchor biosynthesis pathway. Consistent with this predicted function, a functional translational fusion with the green fluorescent protein (GFP) was targeted to the endoplasmic reticulum. Moreover, the mutant exhibited an altered cell wall and addition of glucosamine relieved growth defects. It is concluded that the GPI anchor biosynthetic pathway is required for morphogenesis, cell wall integrity and pathogenicity in Leptosphaeria maculans.
Remy
Estelle
E
INRA, UMR 1290 BIOGER, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
Meyer
Michel
M
INRA, UMR 1290 BIOGER, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
Blaise
Françoise
F
INRA, UMR 1290 BIOGER, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
Simon
Uwe K
UK
Lehrstuhl Spezielle Botanik und Mykologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany.
Kuhn
Diana
D
Lehrstuhl Spezielle Botanik und Mykologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany.
Chabirand
Mélanie
M
INRA, UMR 1290 BIOGER, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
Riquelme
Meritxell
M
Centro de Investigación Científica y de Educación Superior de Ensenada, Departamento de Microbiología, Edificio DBEA, Km. 107 Ctra. Tijuana-Ensenada, 22860 Ensenada, Baja California, Mexico.
Balesdent
Marie-Hélène
MH
INRA, UMR 1290 BIOGER, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
Rouxel
Thierry
T
INRA, UMR 1290 BIOGER, Route de Saint-Cyr, F-78026 Versailles Cedex, France.
D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D001937:Brassica / Q000382:microbiology; D002473:Cell Wall / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D015870:Gene Expression; D020868:Gene Silencing; D017261:Glycosylphosphatidylinositols / Q000096:biosynthesis* / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000032:analysis; D008565:Membrane Proteins / Q000737:chemistry; D009024:Morphogenesis / Q000235:genetics*; D016254:Mutagenesis, Insertional; D009997:Osmotic Pressure; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000032:analysis; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry
D005656:Fungal Proteins; D017261:Glycosylphosphatidylinositols; C448723:Gpi15 protein, S cerevisiae; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins