A fungal metallothionein is required for pathogenicity of Magnaporthe grisea.
The causal agent of rice blast disease, the ascomycete fungus Magnaporthe grisea, infects rice (Oryza sativa) plants by means of specialized infection structures called appressoria, which are formed on the leaf surface and mechanically rupture the cuticle. We have identified a gene, Magnaporthe metallothionein 1 (MMT1), which is highly expressed throughout growth and development by M. grisea and encodes an unusual 22-amino acid metallothionein-like protein containing only six Cys residues. The MMT1-encoded protein shows a very high affinity for zinc and can act as a powerful antioxidant. Targeted gene disruption of MMT1 produced mutants that show accelerated hyphal growth rates and poor sporulation but had no effect on metal tolerance. Mmt1 mutants are incapable of causing plant disease because of an inability to bring about appressorium-mediated cuticle penetration. Mmt1 appears to be distributed in the inner side of the cell wall of the fungus. These findings indicate that Mmt1-like metallothioneins may play a novel role in fungal cell wall biochemistry that is required for fungal virulence.
Tucker
Sara L
SL
School of Biological Sciences, University of Exeter, Washington Singer Laboratories, Exeter EX4 4QG, United Kingdom.
Thornton
Christopher R
CR
Tasker
Karen
K
Jacob
Claus
C
Giles
Greg
G
Egan
Martin
M
Talbot
Nicholas J
NJ
D000595:Amino Acid Sequence; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D001467:Hordeum / Q000382:microbiology; D025301:Hyphae / Q000235:genetics / Q000254:growth & development; D020082:Magnaporthe / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity*; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology; D018384:Oxidative Stress; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D011485:Protein Binding; D021381:Protein Transport; D013172:Spores, Fungal / Q000235:genetics / Q000254:growth & development; D014774:Virulence; D015032:Zinc / Q000378:metabolism
D000975:Antioxidants; D005656:Fungal Proteins; D008668:Metallothionein; D015032:Zinc