title: Strigolactone and cytokinin act antagonistically in regulating rice mesocotyl elongation in darkness.
abstract: Strigolactones (SLs) are a group of phytohormones that control plant growth and development including shoot branching. Previous studies of the phenotypes of SL-related rice (Oryza sativa) dwarf (d) mutants demonstrated that SLs inhibit mesocotyl elongation by controlling cell division. Here, we found that the expression of cytokinin (CK)-responsive type-A RESPONSE REGULATOR (RR) genes was higher in d10-1 and d14-1 mutants than in the wild type. However, CK levels in mesocotyls of the d mutants were not very different from those in the wild type. On the other hand, application of a synthetic CK (kinetin) enhanced mesocotyl elongation in the d mutants and the wild type. d10-1 and d14-1 mesocotyls were more sensitive to CK than wild-type mesocotyls, suggesting that the up-regulation of the CK-responsive type-A RR genes and the higher elongation of mesocotyls in the d mutants are mainly due to the increased sensitivity of the d mutants to CK. Co-treatment with kinetin and a synthetic SL (GR24) confirmed the antagonistic functions of SL and CK on mesocotyl elongation. OsTCP5, which encodes a transcription factor belonging to the cell division-regulating TCP family, was also regulated by SL and CK and its expression was negatively correlated with mesocotyl length. These findings suggest that OsTCP5 contributes to the SL- and CK-controlled mesocotyl elongation in darkness.
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-8657 Japan.
authors.forename: Zhongyuan
authors.initials: Z
authors.lastname: Hu
authors.forename: Takaki
authors.initials: T
authors.lastname: Yamauchi
authors.forename: Jinghua
authors.initials: J
authors.lastname: Yang
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Jikumaru
authors.forename: Tomoko
authors.initials: T
authors.lastname: Tsuchida-Mayama
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ichikawa
authors.forename: Itsuro
authors.initials: I
authors.lastname: Takamure
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nagamura
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tsutsumi
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Junko
authors.initials: J
authors.lastname: Kyozuka
authors.forename: Mikio
authors.initials: M
authors.lastname: Nakazono
mesh_terms: D018548:Cotyledon / Q000254:growth & development*; D003583:Cytokinins / Q000494:pharmacology*; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007701:Kinetin / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology*; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D003583:Cytokinins; C507382:GR24 compound; D007783:Lactones; D007701:Kinetin
keywords: Cytokinin; Mesocotyl; Rice; Strigolactone