Identification and characterization of Arabidopsis gibberellin receptors.
Three gibberellin (GA) receptor genes (AtGID1a, AtGID1b and AtGID1c), each an ortholog of the rice GA receptor gene (OsGID1), were cloned from Arabidopsis, and the characteristics of their recombinant proteins were examined. The GA-binding activities of the three recombinant proteins were confirmed by an in vitro assay. Biochemical analyses revealed similar ligand selectivity among the recombinants, and all recombinants showed higher affinity to GA(4) than to other GAs. AtGID1b was unique in its binding affinity to GA(4) and in its pH dependence when compared with the other two, by only showing binding in a narrow pH range (pH 6.4-7.5) with 10-fold higher affinity (apparent K(d) for GA(4) = 3 x 10(-8) m) than AtGID1a and AtGID1c. A two-hybrid yeast system only showed in vivo interaction in the presence of GA(4) between each AtGID1 and the Arabidopsis DELLA proteins (AtDELLAs), negative regulators of GA signaling. For this interaction with AtDELLAs, AtGID1b required only one-tenth of the amount of GA(4) that was necessary for interaction between the other AtGID1s and AtDELLAs, reflecting its lower K(d) value. AtDELLA boosted the GA-binding activity of AtGID1 in vitro, which suggests the formation of a complex between AtDELLA and AtGID1-GA that binds AtGID1 to GA more tightly. The expression of each AtGID1 clone in the rice gid1-1 mutant rescued the GA-insensitive dwarf phenotype. These results demonstrate that all three AtGID1s functioned as GA receptors in Arabidopsis.
Nakajima
Masatoshi
M
Department of Applied Biological Chemistry, The University of Tokyo, Tokyo 113-8657, Japan. nkjm@pgr1.ch.a.u-tokyo.ac.jp
Shimada
Asako
A
Takashi
Yoshiyuki
Y
Kim
Young-Cheon
YC
Park
Seung-Hyun
SH
Ueguchi-Tanaka
Miyako
M
Suzuki
Hiroyuki
H
Katoh
Etsuko
E
Iuchi
Satoshi
S
Kobayashi
Masatomo
M
Maeda
Tatsuya
T
Matsuoka
Makoto
M
Yamaguchi
Isomaro
I
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005816:Genetic Complementation Test; D005875:Gibberellins / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000033:anatomy & histology / Q000235:genetics; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000033:anatomy & histology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; C512225:GID1a protein, Arabidopsis; C512226:GID1b protein, Arabidopsis; C512227:GID1c protein, Arabidopsis; D005875:Gibberellins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins