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A double mutant for theCYP85A1 andCYP85A2 Genes ofArabidopsis exhibits a Brassinosteroid dwarf phenotype

한국식물학회지 2005년 48권 2호 p.237 ~ 244
Kwon Mi, Fujioka Shozo, 전지현, 김호방, Takatsuto Suguru, Yoshida Shigeo, 안정선, Choe Sung-Hwa,
소속 상세정보
 ( Kwon Mi ) - Seoul National University College of Natural Sciences Department of Biological Sciences
 ( Fujioka Shozo ) - RIKEN
전지현 ( Jeon Ji-Hyun ) - Seoul National University College of Natural Sciences Department of Biological Sciences
김호방 ( Kim Ho-Bang ) - Seoul National University College of Natural Sciences Department of Biological Sciences
 ( Takatsuto Suguru ) - Joetsu University of Education Department of Chemistry
 ( Yoshida Shigeo ) - RIKEN
안정선 ( An Chung-Sun ) - Seoul National University College of Natural Sciences Department of Biological Sciences
 ( Choe Sung-Hwa ) - Seoul National University College of Natural Sciences Department of Biological Sciences

Abstract


Brassinosteroid (BR)-6-oxidases mediate the bridge reactions that connect the late and early C-6 oxidation pathways by converting 6-deoxoBR to 6-oxoBRs. Two similar genes ofArabidopsis, CYP85A1 (At5g38970) andCYP85A2 (At3g30180), are proposed to encode BR-6-oxidases based on findings that heterologously expressed genes mediate BR-6-oxidation reactions in yeast. However, genetic evidence that both genes are critically involved in the BR-6-oxidation step inArabidopsis has been limited. Here, we show that a double mutant for the two genes displays dwarfism similar to that of typical BR biosynthesis-deficient mutants, suggesting that they are the major BR-6-oxidases inArabidopsis. Examination of endogenous BR levels and metabolism monitoring tests using this double mutant revealed a great reduction in the levels of 6-oxoBRs, e.g., TY and CS, due to a lack in the conversion reactions from 6-deoxoCS to CS, and from 6-deoxoTY to TY. Surprisingly, the double mutant accumulated a significant amount of 6-oxocampestanol, suggesting that the upstream C-6 oxidation of campestanol to 6-oxocampestanol is not catalyzed by the two BR-6-oxidases inArabidopsis, rather, by another enzyme yet to be discovered.

키워드

brassinosteroid; BR-6-oxidase; C-6 oxidation; cell elongation; CYP85; cytochrome P450

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