Regulation of castasterone level in primary roots of maize, Zea mays |
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| Authors: | Young-Soo Kim Tae-Wuk Kim Soo Chul Chang Richard P. Pharis June Seung Lee Tae-Jin Han Suguru Takatsuto Hyeonsook Cheong Seong-Ki Kim |
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| Affiliation: | Department of Life Science, Chung-Ang University, Seoul 156-756, Korea; Department of Biology, University College, Yonsei University, Seoul 120-749, Korea; Department of Biological Science, University of Calgary, Calgary, Alberta T2N 1N4, Canada; Department of Biological Science, Ewha Womans University, Seoul 120-750, Korea; Department of Life Science, Hallym University, Chuncheon 200-701, Korea; Department of Chemistry, Joetsu University of Education, Joetsu-shi, Niigata 943-8512, Japan; Department of Genetic Engineering, Chosun University, Kwangju 501-759, Korea |
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| Abstract: | Gas chromatography–mass spectrometry analysis revealed that primary roots of maize contain 28-norcastasterone (28-norCS) and its biosynthetic precursors, cholesterol, and cholestanol, which suggests that the C27-brassinosteroid (C27-BR) biosynthetic pathway to generate 28-norCS is operative in the roots. A cell-free enzyme solution prepared from maize roots successfully mediated C24-methylation of 28-norCS to produce castasterone (CS) with the aid of S-adenosyl- l -methionine, which indicates that CS can be generated through C27-BR biosynthesis, as well as C28-BR biosynthesis, in maize roots. Enzymatic conversion study using the cell-free enzyme solution demonstrated that CS is converted into 26-norCS in the enzyme solution. Exogenously applied 28-norCS and 26-norCS showed less activity than CS in the activation of gravitropic curvature and inhibition of root elongation. Taken together, a steady-state level of CS, the active BR in maize roots, seems to be strictly controlled by complicated processes such as C28- and C27-BR biosynthesis and biodegradation by C26-demethylation to exert its biological activity. |
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