title: Small GTPase Rac1 and its interaction partner Cla4 regulate polarized growth and pathogenicity in Verticillium dahliae.
abstract: Rac1 is a small GTPase coordinating diverse cellular functions such as cell polarity, vesicular trafficking, the cell cycle and transcriptional dynamics in many organisms. In this study, we investigate the biological functions of VdRac1, a Rac1 homolog in the soil-borne, wilt-causing fungus Verticillium dahliae. The VdRac1 gene was deleted in a V. dahliae virulence strain Vd8 isolated from a local cotton cultivar. ΔVdrac1 mutants display drastic reduction in colony expansion and form compact, convoluted colonies, show hyper-branching, loss of polarity and ability to penetrate, leading to severely reduced virulence. The p21-activated kinase Cla4 (named as VdCla4 in V. dahliae) null mutants ΔVdcla4 share identical phenotypes with ΔVdrac1. Yeast two-hybrid studies prove that VdCla4 is an effector of VdRac1. Localizations of actin and reactive oxygen species (ROS) in ΔVdrac1 and ΔVdcla4 compared with the corresponding wild-type strain reveal that VdRac1 and VdCla4 play a primary role in polarized hyphal growth via organization of ROS and play only a minor role in the organization of actin. The Vdrac1 and Vdcla4 null mutants are defective in conidiation and trace elements can partially compensate for the defect. Our data demonstrate that VdRac1 regulates polarized growth and pathogenicity by interacting with its effector VdCla4 in V. dahliae.
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tian
authors.affiliation: The State Key Laboratory of Crop Genetics & Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.affiliation: The State Key Laboratory of Crop Genetics & Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Wangzhen
authors.initials: W
authors.lastname: Guo
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, PR China. Electronic address: xywang@njau.edu.cn.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Wang
mesh_terms: D000199:Actins; D016764:Cell Polarity; D049109:Cell Proliferation; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D055785:Gene Knockdown Techniques; D025301:Hyphae / Q000254:growth & development*; D010935:Plant Diseases / Q000382:microbiology; D017382:Reactive Oxygen Species; D013172:Spores, Fungal / Q000254:growth & development; D020172:Verticillium / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics; D020830:rac1 GTP-Binding Protein / Q000235:genetics* / Q000502:physiology
chemical_list: D000199:Actins; D005656:Fungal Proteins; D017382:Reactive Oxygen Species; D020830:rac1 GTP-Binding Protein
keywords: Pathogenicity; Polarized growth; Small GTPase Rac1; p21-activated kinase Cla4