A rice semi-dwarf gene, Tan-Ginbozu (D35), encodes the gibberellin biosynthesis enzyme, ent-kaurene oxidase.
A rice (Oryza sativa L.) semi-dwarf cultivar, Tan-Ginbozu (d35Tan-Ginbozu), contributed to the increase in crop productivity in Japan in the 1950s. Previous studies suggested that the semi-dwarf stature of d35Tan-Ginbozu is caused by a defective early step of gibberellin biosynthesis, which is catalyzed by ent-kaurene oxidase (KO). To study the molecular characteristics of d35Tan-Ginbozu, we isolated 5 KO-like (KOL) genes from the rice genome, which encoded proteins highly homologous to Arabidopsis and pumpkin KOs. The genes (OsKOL1 to 5) were arranged as tandem repeats in the same direction within a 120 kb sequence. Expression analysis revealed that OsKOL2 and OsKOL4 were actively transcribed in various organs, while OsKOL1 and OsKOL5 were expressed only at low levels; OsKOL3 may be a pseudogene. Sequence analysis and complementation experiments demonstrated that OsKOL2 corresponds to D35. Homozygote with null alleles of D35 showed a severe dwarf phenotype; therefore, d35Tan-Ginbozu is a weak allele of D35. Introduction of OsKOL4 into d35Tan-Ginbozu did not rescue its dwarf phenotype, indicating that OsKOL4 is not involved in GA biosynthesis. OsKOL4 and OsKOL5 are likely to take part in phytoalexin biosynthesis, because their expression was promoted by UV irradiation and/or elicitor treatment. Comparing d35Tan-Ginbozu with other high yielding cultivars, we discuss strategies to produce culm architectures suitable for high crop yield by decreasing GA levels.
Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi 464-8601, Japan.
Hironori
H
Itoh
Tomoko
T
Tatsumi
Tomoaki
T
Sakamoto
Kazuko
K
Otomo
Tomonobu
T
Toyomasu
Hidemi
H
Kitano
Motoyuki
M
Ashikari
Shigeyuki
S
Ichihara
Makoto
M
Matsuoka
D000595:Amino Acid Sequence; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D023061:Gene Order; D005816:Genetic Complementation Test; D005875:Gibberellins / Q000096:biosynthesis*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009154:Mutation; D009844:Oligosaccharides / Q000494:pharmacology; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D010936:Plant Extracts / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012717:Sesquiterpenes; D013729:Terpenes; D014466:Ultraviolet Rays; D000094162:Phytoalexins
D005875:Gibberellins; D007527:Isoenzymes; D009844:Oligosaccharides; D010936:Plant Extracts; D012717:Sesquiterpenes; D013729:Terpenes; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C066398:ent-kaurene oxidase; D000094162:Phytoalexins