title: SWAP70 functions as a Rac/Rop guanine nucleotide-exchange factor in rice.
abstract: Rho family small GTPases are involved in diverse signaling processes including immunity, growth, and development. The activity of Rho GTPases is regulated by cycling between guanosine diphosphate (GDP)-bound inactive and guanosine triphosphate (GTP)-bound active forms, in which guanine nucleotide exchange factors (GEFs) predominantly function to promote activation of the GTPases. In animals, most Rho GEFs possess a Dbl (diffuse B-cell lymphoma) homology (DH) domain which functions as a GEF-catalytic domain. However, no proteins with the DH domain have been identified in plants so far. Instead, plant-specific Rho GEFs with the PRONE domain responsible for GEF activity have been found to constitute a large family in plants. In this study, we found rice homologs of human SWAP70, Oryza sativa (Os) SWAP70A and SWAP70B, containing the DH domain. OsSWAP70A interacted with rice Rho GTPase OsRac1, an important signaling factor for immune responses. The DH domain of OsSWAP70A exhibited the GEF-catalytic activity toward OsRac1 as found in animal Rho GEFs, indicating that plants have the functional DH domains. Transient expression of OsSWAP70A enhanced OsRac1-mediated production of reactive oxygen species in planta. Reduction of OsSWAP70A and OsSWAP70B mRNA levels by RNA interference resulted in the suppression of chitin elicitor-induced defense gene expression and ROS production. Thus, it is likely that OsSWAP70 regulates immune responses through activation of OsRac1.
authors.affiliation: Department of Advanced Bioscience, Graduate School of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Keiko
authors.initials: K
authors.lastname: Imai
authors.forename: Akira
authors.initials: A
authors.lastname: Akamatsu
authors.forename: Masanori
authors.initials: M
authors.lastname: Mihashi
authors.forename: Nagao
authors.initials: N
authors.lastname: Hayashi
authors.forename: Ko
authors.initials: K
authors.lastname: Shimamoto
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kawasaki
mesh_terms: D000595:Amino Acid Sequence; D015870:Gene Expression / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D010802:Phylogeny; D057865:Plant Immunity / Q000235:genetics*; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D017382:Reactive Oxygen Species; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins