title: Molecular actions of two synthetic brassinosteroids, iso-carbaBL and 6-deoxoBL, which cause altered physiological activities between Arabidopsis and rice.
abstract: Brassinosteroid (BR) is an important plant hormone that is perceived by the BRASSINOSTEROID INSENSITIVE 1 (BRI1) receptor. BRI1 is conserved among dicot and monocot species; however, the molecular mechanism underlying BR perception in monocots is not fully understood. We synthesised two BRs, iso-carbabrassinolide (iso-carbaBL) and 6-deoxoBL, which have different BR activities in Arabidopsis thaliana (Arabidopsis) and rice. Our bioassay indicated that iso-carbaBL has relatively strong BR activity in Arabidopsis, but is inactive in rice and competitively inhibits BR activity. The bioactivity of 6-deoxoBL was similar to that of BL in Arabidopsis, but was much lower in rice. Binding experiments using recombinant Arabidopsis and rice BRI1 protein fragments suggested that iso-carbaBL and 6-deoxoBL bind to both receptors. These results showed that iso-carbaBL and 6-deoxoBL act as an antagonist and agonist, respectively, of BRs in rice. A docking simulation analysis suggested that iso-carbaBL fits deeper in the binding pocket to block the binding of active BR to rice BRI1. The simulated binding energy of 6-deoxoBL with rice BRI1 is much lower than that with Arabidopsis BRI1. The possible structural characteristics of rice BRI1 were determined based on the difference in the BR activities of iso-carbaBL and 6-deoxoBL in Arabidopsis and rice.
authors.affiliation: RIKEN, Wako, Saitama, Japan.
authors.forename: Ayako
authors.identifier: http://orcid.org/0000-0002-5181-7331
authors.initials: A
authors.lastname: Nakamura
authors.affiliation: RIKEN Systems and Structural Biology Center, Tsurumi, Yokohama, Kanagawa, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Tochio
authors.affiliation: RIKEN, Wako, Saitama, Japan.
authors.forename: Shozo
authors.initials: S
authors.lastname: Fujioka
authors.affiliation: Graduate School of Agricultural and Life Science, The University of Tokyo, Yayoi, Bunkyo, Tokyo, Japan.
authors.forename: Shinsaku
authors.initials: S
authors.lastname: Ito
authors.affiliation: RIKEN Systems and Structural Biology Center, Tsurumi, Yokohama, Kanagawa, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Kigawa
authors.affiliation: RIKEN, Plant Science Center, Tsurumi, Yokohama, Kanagawa, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Shimada
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Aichi, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Matsuoka
authors.affiliation: RIKEN, Wako, Saitama, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Kinoshita
authors.affiliation: Graduate School of Agricultural and Life Science, The University of Tokyo, Yayoi, Bunkyo, Tokyo, Japan.|JST-CREST, Kawaguchi, Saitama, Japan.
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.affiliation: RIKEN, Wako, Saitama, Japan.
authors.forename: Hideharu
authors.initials: H
authors.lastname: Seto
authors.affiliation: RIKEN, Wako, Saitama, Japan.|JST-CREST, Kawaguchi, Saitama, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D060406:Brassinosteroids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D017343:Genes, Plant / Q000187:drug effects; D062105:Molecular Docking Simulation; D012275:Oryza / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D010937:Plant Growth Regulators / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism; D013045:Species Specificity
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D010937:Plant Growth Regulators; D011494:Protein Kinases; C519615:BRI1 protein, Oryza sativa; C108270:BRI1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases