Rac1 Is Required for Pathogenicity and Chm1-Dependent Conidiogenesis in Rice Fungal Pathogen Magnaporthe grisea

PLoS Pathogens

Zonghua Wang¹  Jisheng Chen²  Shiqin Zheng²  Weijian Sang³  Dongmei Zhang³  Guodong Lu³  Wu Zheng⁴  Xiao Chen⁴  Guangpu Li⁴ 

[1] Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America;Key Laboratory of Biopesticide and Chemistry Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, China;Plant Protection College, Fujian Agriculture and Forestry University, Fuzhou, China;The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China

关键词: Deletion mutagenesis;    Rice blast fungus;    Pathogenesis;    Rice;    Polymerase chain reaction;    Fungi;    Appressoria;    Superoxides;   

DOI  :  10.1371/journal.ppat.1000202

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Rac1 is a small GTPase involved in actin cytoskeleton organization and polarized cell growth in many organisms. In this study, we investigate the biological function of MgRac1, a Rac1 homolog in Magnaporthe grisea. The Mgrac1 deletion mutants are defective in conidial production. Among the few conidia generated, they are malformed and defective in appressorial formation and consequently lose pathogenicity. Genetic complementation with native MgRac1 fully recovers all these defective phenotypes. Consistently, expression of a dominant negative allele of MgRac1 exhibits the same defect as the deletion mutants, while expression of a constitutively active allele of MgRac1 can induce abnormally large conidia with defects in infection-related growth. Furthermore, we show the interactions between MgRac1 and its effectors, including the PAK kinase Chm1 and NADPH oxidases (Nox1 and Nox2), by the yeast two-hybrid assay. While the Nox proteins are important for pathogenicity, the MgRac1-Chm1 interaction is responsible for conidiogenesis. A constitutively active chm1 mutant, in which the Rac1-binding PBD domain is removed, fully restores conidiation of the Mgrac1 deletion mutants, but these conidia do not develop appressoria normally and are not pathogenic to rice plants. Our data suggest that the MgRac1-Chm1 pathway is responsible for conidiogenesis, but additional pathways, including the Nox pathway, are necessary for appressorial formation and pathogenicity.

【 授权许可】

CC BY