title: WRKY45-dependent priming of diterpenoid phytoalexin biosynthesis in rice and the role of cytokinin in triggering the reaction.
abstract: Plant activators such as benzothiadiazole (BTH) protect plants against diseases by priming the salicylic acid (SA) signaling pathway. In rice, the transcription factor WRKY45 plays a central role in this process. To investigate the mechanism involved in defense-priming by BTH and the role of WRKY45 in this process, we analyzed the transcripts of biosynthetic genes for diterpenoid phytoalexins (DPs) during the rice-Magnaporthe oryzae interaction. The DP biosynthetic genes were barely upregulated in BTH-treated rice plants, but were induced rapidly after M. oryzae infection in a WRKY45-dependent manner. These results indicate that the DP biosynthetic genes were primed by BTH through WRKY45. Rapid induction of the DP biosynthetic genes was also observed after M. oryzae infection to WRKY45-overexpressing (WRKY45-ox) plants. The changes in gene transcription resulted in accumulation of DPs in WRKY45-ox and BTH-pretreated rice after M. oryzae infection. Previously, we reported that cytokinins (CKs), especially isopentenyladenines, accumulated in M. oryzae-infected rice. Here, we show that DP biosynthetic genes are regulated by the SA/CK synergism in a WRKY45-dependent manner. Together, we propose that CK plays a role in mediating the signal of M. oryzae infection to trigger the induction of DP biosynthetic genes in BTH-primed plants.
authors.affiliation: Disease Resistant Crops Research Unit, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Akagi
authors.forename: Setsuko
authors.initials: S
authors.lastname: Fukushima
authors.forename: Kazunori
authors.initials: K
authors.lastname: Okada
authors.forename: Chang-Jie
authors.initials: CJ
authors.lastname: Jiang
authors.forename: Riichiro
authors.initials: R
authors.lastname: Yoshida
authors.forename: Akira
authors.initials: A
authors.lastname: Nakayama
authors.forename: Masaki
authors.initials: M
authors.lastname: Shimono
authors.forename: Shoji
authors.initials: S
authors.lastname: Sugano
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Yamane
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takatsuji
mesh_terms: D003583:Cytokinins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004224:Diterpenes / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012717:Sesquiterpenes / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000094162:Phytoalexins
chemical_list: D003583:Cytokinins; D004224:Diterpenes; D010940:Plant Proteins; D012717:Sesquiterpenes; D014157:Transcription Factors; D000094162:Phytoalexins