MST12 regulates infectious growth but not appressorium formation in the rice blast fungus Magnaporthe grisea.
In the rice blast fungus Magnaporthe grisea, a mitogen-activated protein kinase gene, PMK1, is known to regulate appressorium formation and infectious hyphae growth. Since PMK1 is homologous to the FUS3 and KSS1 genes that regulate the transcription factor STE12 in yeast, we functionally characterized the STE12 homologue in M. grisea (MST12). A polymerase chain reaction-based approach was used to isolate the MST12 gene that is homologous to yeast STE12. Four mst12 deletion mutants were isolated by gene replacement. No obvious defect in vegetative growth, conidiation, or conidia germination was observed in mst12 mutants. However, mst12 mutants were nonpathogenic on rice and barley leaves. In contrast to pmk1 mutants that did not form appressoria, mst12 mutants produced typical dome-shaped and melanized appressoria. However, the appressoria formed by mst12 mutants failed to penetrate onion epidermal cells. When inoculated through wound sites, mst12 mutants failed to cause spreading lesions and appeared to be defective in infectious growth. These data indicate that MST12 may function downstream of PMK1 to regulate genes involved in infectious hyphae growth. A transcription factor or factors other than MST12 must exist in M. grisea and function downstream from PMK1 for appressorium formation.
Park
Gyungsoon
G
Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907 USA.
Xue
Chaoyang
C
Zheng
Li
L
Lam
Stephen
S
Xu
Jin-Rong
JR
D000595:Amino Acid Sequence; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005658:Fungi / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D020037:Sordariales / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D005656:Fungal Proteins; D014157:Transcription Factors; D020928:Mitogen-Activated Protein Kinases