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Published on: October 4, 2019
Rice CYP734As function as multisubstrate and multifunctional enzymes in brassinosteroid catabolism
Tomoaki Sakamoto1, Ayami Kawabe, Asako Tokida-Segawa
1Institute for Advanced Research, Nagoya University, Nagoya, Aichi 464-8601, Japan. sakamoto@iar.nagoya-u.ac.jp
The Plant Journal : for Cell and Molecular Biology
|March 23, 2011
Summary
Rice CYP734A enzymes inactivate brassinosteroids, regulating plant growth. These multifunctional enzymes control brassinosteroid levels by direct inactivation and by suppressing biosynthesis, impacting plant development.
Area of Science:
- Plant Biology
- Biochemistry
- Molecular Biology
Background:
- Brassinosteroids are crucial plant hormones regulating growth and development.
- The catabolism of brassinosteroids maintains endogenous hormone levels.
- Arabidopsis thaliana utilizes CYP734A1/BAS1 for brassinosteroid inactivation.
Purpose of the Study:
- To characterize the function of Oryza sativa (rice) CYP734A orthologs.
- To investigate the role of rice CYP734As in brassinosteroid metabolism.
- To understand how these enzymes regulate brassinosteroid homeostasis in rice.
Main Methods:
- Gene expression analysis of rice CYP734A orthologs.
- Generation and phenotypic analysis of transgenic rice overexpressing rice CYP734As.
- Biochemical characterization of recombinant rice CYP734A enzymes using brassinosteroid intermediates.
Main Results:
- Overexpression of rice CYP734As induced brassinosteroid-deficient phenotypes in transgenic rice.
- Transgenic rice lines showed deficiencies in bioactive castasterone (CS) and its precursors.
- Recombinant rice CYP734As demonstrated substrate specificity for C-22 hydroxylated brassinosteroid intermediates.
- Rice CYP734As exhibited multifunctional activity, catalyzing C-26 hydroxylation, oxidation, and carboxyl group formation in vitro.
Conclusions:
- Rice CYP734As are multifunctional enzymes involved in brassinosteroid catabolism.
- These enzymes regulate endogenous bioactive brassinosteroid levels through direct inactivation of CS.
- Rice CYP734As also suppress CS biosynthesis by reducing precursor levels, thereby controlling plant development.
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