title: Structural Requirements of Strigolactones for Shoot Branching Inhibition in Rice and Arabidopsis.
abstract: The structural requirements of strigolactones (SLs) involved in germination induction of root parasitic plants and hyphal branching in arbuscular mycorrhizal (AM) fungi have been extensively studied. However, our knowledge of the requirements of SLs involved in shoot branching inhibition in plants is still limited. To address this question, we investigated the structure-activity relationships of SLs in shoot branching inhibition in rice and Arabidopsis. SLs possess a four-ring structure, with a tricyclic lactone (ABC-rings) connected to a methylbutenolide part (D-ring) via an enol ether bridge. Here, we show that the the (R) configuration at C-2', which determines the steric position of the D-ring relative to the enol ether olefin bond, is critical for the hormonal activity in rice. Replacement of the enol ether moiety by an alkoxy or imino ether resulted in a severe reduction in biological activity in rice. Moreover, yeast two-hybrid experiments using a possible SL receptor, DWARF14 (D14), and a repressor in the SL signaling pathway, DWARF53 (D53), showed that D14 can interact with D53 in the presence of (2'R) stereoisomers of SLs, but not (2'S) stereoisomers, suggesting that the stereostructure of SLs is crucial for the interaction of these proteins. When GR5, an AB-ring-truncated analog, was applied to the hydroponic culture medium, strong inhibition of shoot branching was observed both in rice and in Arabidopsis. However, GR5 was only weakly active when directly applied to the axillary buds of Arabidopsis. Our results indicate that the difference in plant species and application methods greatly influences the apparent SL biological activity.
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan Graduate School of Life Sciences, Toyo University, Itakura-machi, Ora-gun, Gunma, 374-0193 Japan These authors contributed equally to this work.
authors.forename: Mikihisa
authors.initials: M
authors.lastname: Umehara
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577 Japan These authors contributed equally to this work.
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Cao
authors.affiliation: Graduate School of life and Environmental Sciences, Osaka Prefecture University, Naka-ku, Sakai, Osaka, 599-8531 Japan.
authors.forename: Kohki
authors.initials: K
authors.lastname: Akiyama
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577 Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Akatsu
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577 Japan.
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Seto
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577 Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hanada
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan Present address: Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan.
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Li
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Takeda-Kamiya
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577 Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Morimoto
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577 Japan shinjiro@m.tohoku.ac.jp.
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Yamaguchi
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development*; D003470:Culture Media; D004986:Ether / Q000737:chemistry; D018525:Germination / Q000187:drug effects; D018527:Hydroponics; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development; D007783:Lactones / Q000737:chemistry / Q000494:pharmacology*; D012275:Oryza / Q000187:drug effects / Q000254:growth & development*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development*; D012639:Seeds / Q000187:drug effects / Q000254:growth & development; D013237:Stereoisomerism; D020798:Two-Hybrid System Techniques
chemical_list: D003470:Culture Media; D007783:Lactones; D004986:Ether
keywords: Arabidopsis thaliana; Oryza sativa; Stereoisomer; Strigolactone