title: Molecular interactions of a soluble gibberellin receptor, GID1, with a rice DELLA protein, SLR1, and gibberellin.
abstract: GIBBERELLIN INSENSITIVE DWARF1 (GID1) encodes a soluble gibberellin (GA) receptor that shares sequence similarity with a hormone-sensitive lipase (HSL). Previously, a yeast two-hybrid (Y2H) assay revealed that the GID1-GA complex directly interacts with SLENDER RICE1 (SLR1), a DELLA repressor protein in GA signaling. Here, we demonstrated, by pull-down and bimolecular fluorescence complementation (BiFC) experiments, that the GA-dependent GID1-SLR1 interaction also occurs in planta. GA(4) was found to have the highest affinity to GID1 in Y2H assays and is the most effective form of GA in planta. Domain analyses of SLR1 using Y2H, gel filtration, and BiFC methods revealed that the DELLA and TVHYNP domains of SLR1 are required for the GID1-SLR1 interaction. To identify the important regions of GID1 for GA and SLR1 interactions, we used many different mutant versions of GID1, such as the spontaneous mutant GID1s, N- and C-terminal truncated GID1s, and mutagenized GID1 proteins with conserved amino acids replaced with Ala. The amino acid residues important for SLR1 interaction completely overlapped the residues required for GA binding that were scattered throughout the GID1 molecule. When we plotted these residues on the GID1 structure predicted by analogy with HSL tertiary structure, many residues were located at regions corresponding to the substrate binding pocket and lid. Furthermore, the GA-GID1 interaction was stabilized by SLR1. Based on these observations, we proposed a molecular model for interaction between GA, GID1, and SLR1.
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, Nagoya 464-8601, Japan. mueguchi@agr.nagoya-u.ac.jp
authors.forename: Miyako
authors.initials: M
authors.lastname: Ueguchi-Tanaka
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakajima
authors.forename: Etsuko
authors.initials: E
authors.lastname: Katoh
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ohmiya
authors.forename: Kenji
authors.initials: K
authors.lastname: Asano
authors.forename: Shoko
authors.initials: S
authors.lastname: Saji
authors.forename: Xiang
authors.initials: X
authors.lastname: Hongyu
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Ashikari
authors.forename: Hidemi
authors.initials: H
authors.lastname: Kitano
authors.forename: Isomaro
authors.initials: I
authors.lastname: Yamaguchi
authors.forename: Makoto
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D004305:Dose-Response Relationship, Drug; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012275:Oryza / Q000187:drug effects / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects; D012995:Solubility / Q000187:drug effects; D013329:Structure-Activity Relationship; D020798:Two-Hybrid System Techniques
chemical_list: D005875:Gibberellins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C007842:gibberellic acid