The role of OsBRI1 and its homologous genes, OsBRL1 and OsBRL3, in rice.
Since first identifying two alleles of a rice (Oryza sativa) brassinosteroid (BR)-insensitive mutant, d61, that were also defective in an orthologous gene in Arabidopsis (Arabidopsis thaliana) BRASSINOSTEROID INSENSITIVE1 (BRI1), we have isolated eight additional alleles, including null mutations, of the rice BRI1 gene OsBRI1. The most severe mutant, d61-4, exhibited severe dwarfism and twisted leaves, although pattern formation and differentiation were normal. This severe shoot phenotype was caused mainly by a defect in cell elongation and the disturbance of cell division after the determination of cell fate. In contrast to its severe shoot phenotype, the d61-4 mutant had a mild root phenotype. Concomitantly, the accumulation of castasterone, the active BR in rice, was up to 30-fold greater in the shoots, while only 1.5-fold greater in the roots. The homologous genes for OsBRI1, OsBRL1 and OsBRL3, were highly expressed in roots but weakly expressed in shoots, and their expression was higher in d61-4 than in the wild type. Based on these observations, we conclude that OsBRI1 is not essential for pattern formation or organ initiation, but is involved in organ development through controlling cell division and elongation. In addition, OsBRL1 and OsBRL3 are at least partly involved in BR perception in the roots.
Nakamura
Ayako
A
Bioscience and Biotechnology Center, Nagoya University Chikusa, Nagoya 464-8601, Japan.
Fujioka
Shozo
S
Sunohara
Hidehiko
H
Kamiya
Noriko
N
Hong
Zhi
Z
Inukai
Yoshiaki
Y
Miura
Kotaro
K
Takatsuto
Suguru
S
Yoshida
Shigeo
S
Ueguchi-Tanaka
Miyako
M
Hasegawa
Yasuko
Y
Kitano
Hidemi
H
Matsuoka
Makoto
M
D000483:Alleles; D000595:Amino Acid Sequence; D002455:Cell Division / Q000235:genetics; D049108:Cell Enlargement; D018519:Meristem / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D018517:Plant Roots / Q000033:anatomy & histology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D012639:Seeds / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment
D010940:Plant Proteins; D011956:Receptors, Cell Surface