title: Regulation of Arabidopsis defense responses against Spodoptera littoralis by CPK-mediated calcium signaling.
abstract: BACKGROUND
  Plant Ca2+ signals are involved in a wide array of intracellular signaling pathways after pest invasion. Ca2+-binding sensory proteins such as Ca2+-dependent protein kinases (CPKs) have been predicted to mediate the signaling following Ca2+ influx after insect herbivory. However, until now this prediction was not testable.
  
  
  RESULTS
  To investigate the roles CPKs play in a herbivore response-signaling pathway, we screened the characteristics of Arabidopsis CPK mutants damaged by a feeding generalist herbivore, Spodoptera littoralis. Following insect attack, the cpk3 and cpk13 mutants showed lower transcript levels of plant defensin gene PDF1.2 compared to wild-type plants. The CPK cascade was not directly linked to the herbivory-induced signaling pathways that were mediated by defense-related phytohormones such as jasmonic acid and ethylene. CPK3 was also suggested to be involved in a negative feedback regulation of the cytosolic Ca2+ levels after herbivory and wounding damage. In vitro kinase assays of CPK3 protein with a suite of substrates demonstrated that the protein phosphorylates transcription factors (including ERF1, HsfB2a and CZF1/ZFAR1) in the presence of Ca2+. CPK13 strongly phosphorylated only HsfB2a, irrespective of the presence of Ca2+. Furthermore, in vivo agroinfiltration assays showed that CPK3-or CPK13-derived phosphorylation of a heat shock factor (HsfB2a) promotes PDF1.2 transcriptional activation in the defense response.
  
  
  CONCLUSIONS
  These results reveal the involvement of two Arabidopsis CPKs (CPK3 and CPK13) in the herbivory-induced signaling network via HsfB2a-mediated regulation of the defense-related transcriptional machinery. This cascade is not involved in the phytohormone-related signaling pathways, but rather directly impacts transcription factors for defense responses.
authors.affiliation: Global COE Program: Evolution and Biodiversity, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Chidananda Nagamangala
authors.initials: CN
authors.lastname: Kanchiswamy
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Takahashi
authors.forename: Stefano
authors.initials: S
authors.lastname: Quadro
authors.forename: Massimo E
authors.initials: ME
authors.lastname: Maffei
authors.forename: Simone
authors.initials: S
authors.lastname: Bossi
authors.forename: Cinzia
authors.initials: C
authors.lastname: Bertea
authors.forename: Simon Atsbaha
authors.initials: SA
authors.lastname: Zebelo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Muroi
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Ishihama
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshioka
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Boland
authors.forename: Junji
authors.initials: J
authors.lastname: Takabayashi
authors.forename: Yaeta
authors.initials: Y
authors.lastname: Endo
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sawasaki
authors.forename: Gen-ichiro
authors.initials: G
authors.lastname: Arimura
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D054883:Oxylipins / Q000378:metabolism; D010766:Phosphorylation; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D005030:Ethylenes; D054883:Oxylipins; D018749:RNA, Plant; D011994:Recombinant Proteins; D014157:Transcription Factors; C011006:jasmonic acid; C036216:ethylene; C516786:CPK3 protein, Arabidopsis; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium