title: Castasterone is a likely end product of brassinosteroid biosynthetic pathway in rice.
abstract: Brassinolide is known to be the most biologically active compound among more than 50 brassinosteroids identified to date. However, brassinolide has not been detected in rice. To determine if this is due to the lack of the brassinolide synthase function in the rice CYP85A enzyme, we performed analyses to study metabolic conversion using a yeast strain harboring the rice CYP85A1 gene. In repeated feeding tests where the substrates were used, the biosynthetic pathway progressed only up to the synthesis of castasterone, not of brassinolide. Phylogenetic analysis of the CYP85 amino acid sequences revealed that duplication of the CYP85 gene has occurred in most dicotyledonous plant genomes; further, 1 of the 2 copies of CYP85 is evolving to develop a brassinolide synthase function. However, only a single copy of this gene is found in the currently available genome sequences of graminaceous plants; this is a likely explanation for the absence of an endogenous pool of brassinolide in rice plants.
authors.affiliation: Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Republic of Korea.
authors.forename: Bo Kyung
authors.initials: BK
authors.lastname: Kim
authors.forename: Shozo
authors.initials: S
authors.lastname: Fujioka
authors.forename: Suguru
authors.initials: S
authors.lastname: Takatsuto
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tsujimoto
authors.forename: Sunghwa
authors.initials: S
authors.lastname: Choe
mesh_terms: D000595:Amino Acid Sequence; D060406:Brassinosteroids; D002777:Cholestanols / Q000378:metabolism*; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D018628:Gene Dosage; D020440:Gene Duplication; D018745:Genome, Plant; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D013256:Steroids / Q000378:metabolism; D013260:Steroids, Heterocyclic / Q000378:metabolism; D015003:Yeasts / Q000201:enzymology / Q000235:genetics
chemical_list: C437447:6-deoxocastasterone; D060406:Brassinosteroids; D002777:Cholestanols; D010940:Plant Proteins; D013256:Steroids; D013260:Steroids, Heterocyclic; C083545:castasterone; D003577:Cytochrome P-450 Enzyme System; C023623:brassinolide