Brassinosteroid biosynthesis

CHOE, S., DILKES, B.P., FUJIOKA, S., TAKATSUTO, S., SAKURAI, A., FELDMANN, K.A., The DWF4 gene of Arabidopsis encodes a cytochrome P450 that mediates multiple 22-hydroxylation steps in brassinosteroid biosynthesis, Plant Cell, 1998,10, 231-243. 

BISHOP, G.J., NOMURA, T., YOKOTA, T., HARRISON, K, NOGUCHI, T., FUJIOKA, S, TAKATSUTO, S., JONES, J.D., KAMIYA, Y., The tomato DWARF enzyme catalyses C-6 oxidation in brassinosteroid biosynthesis, Proc. Natl. Acad. Sci. USA, 1999, 96, 1761-6. 

Some biochemical functions defined by the Arabidopsis dwarf mutants were later confirmed by heterologous expression of genes and by in vivo conversion of postulated substrates [17-20]. As part of these physiological and biochemical studies, tomato cell suspension cultures have also been established to investigate intermediates and enzymes of brassinosteroid biosynthesis and metabolism [21-23]. Enzyme activities from partially purified protein extracts were first detected in this model system [24]. 

Fig. (1). Proposed pathways and genes involved in sterol and brassinosteroid biosynthesis.

Most known brassinosteroid mutants are defective in genes that code for enzymes required for the biosynthesis of brassinosteroid precursors. This chapter will summarize the upstream part of brassinosteroid biosynthesis pathway. 

Another dwarf mutant of Arabidopsis, sax], defines a step upstream of DWF1 in the brassinosteroid biosynthesis pathway [27]. Rescue experiments with intermediates showed that saxl is involved in the oxidation and isomerization of 3P-hydroxyl,A5 6 precursors to 3-oxo-A4 5 steroids (Fig. (4)). 

This chapter deals with the conversion from cathasterone to brassinolide, the biologically most active brassinosteroid. Only two mutants have been found to be involved in the downstream subpathway. Nevertheless, enzyme activities from enriched protein fractions have first been detected in this part of brassinosteroid biosynthesis. 

An enormous progress in investigating the brassinosteroid biosynthesis was made by mutant analysis and the use of very sensitive analytical methods, leading within few years to a logical and very attractive putative biosynthetic pathway. 

Figure 32 Structures of triazole inhibitors of brassinosteroid biosynthesis.

Asami, T., Min, Y., Nagata, N., Yamagishi, K., Takatsuto, S., Fujioka, S., Muro-fushi, N., Yamaguchi, I. and Yoshida, S. (2000) Characterization of brassina-zole, a triazole-type brassinosteroid biosynthesis inhibitor. Plant Physiol., 123, 93-9. 

Asami, T. and Yoshida, S. (1999) Brassinosteroid biosynthesis inhibitors. Trends Plant Sci., 4, 348-53. 

Fujioka, S., Li, J., Choi, Y., Seto, H., Takatsuto, S., Noguchi, T., Watanabe, T., Kuriyama, H., Yokota, T., Chory, J. and Sakurai, A. (1997) The Arabidopsis deetiolated2 mutant is blocked early in brassinosteroid biosynthesis. Plant Cell, 9, 1951-62. 

Koka, C.V., Cemy, R.E., Gardner, R.G., Noguchi, T, Fujioka, S., Takatsuto, S., Yoshida, S. and Clouse, S.D. (2000) A putative role for the tomato genes DUMPY and CURL-3 in brassinosteroid biosynthesis and response. Plant Physiol, 122, 85-98. 

Ohnishi, T., Szatmari, A., Watanabe, B., Fujita, S., Bancos, S., Koncz, C., Lafos, M., Shibata, K., Yokota, T., Sakata, K., Szekeres, M. and Mizutani, M. (2006) C-23 Hy-droxylation by Arabidopsis CYP90C1 and CYP90D1 reveals a novel shortcut in brassinosteroid biosynthesis. Plant Cell, 18, 3275-88. 

Ambidopsis and tomato catalyse multiple C-6 oxidations in brassinosteroid biosynthesis. Plant Physiol., 126, 770-9. 

Wang, Z., Nakano, T., Gendron, J., He, J., Chen, M., Vafeados, D., Yang, Y., Fu-jioka, S., Yoshida, S., Asami, T. and Chory, J. (2002) Nuclear-localized BZRl mediates brassinosteroid-induced growth and feedback suppression of brassinosteroid biosynthesis. Dev. Cell, 2, 505-13. 

Shimada, Y., S. Fujioka, N. Miyaushi, M. Kushiro, S. Takatsuto, T. Nomura et al. (2001). Brassinosteroid 6-oxidases from Arabidopsis and tomato catalyze multiple C-6 oxidations in brassinosteroid biosynthesis. Plant Physiol. 126, 770-779. 

G.J. Bishop, C.M. Koncz et al. (2002). Regulation of transcript levels of the Arabidopsis cytochrome P450 genes involved in brassinosteroid biosynthesis. Plant Physiol. 130, 504-513. 

Figure 2. Chemical structures of brassinosteroid biosynthesis inhibitors.

Chemical Genetics, Brassinosteroids, Biosynthesis, Inhibitors, Abscisic Acid, Carotenoid Cleavage Dioxygenase, Nine-cis-carotenoid Dioxygenase, Chemical Biology... 

Screening of Arabidopsis mutant by phytohormone brassinosteroid biosynthesis inhibitor (Brz) (T. Komatsu, Tokyo Univ. ofAgric. Tech., Japan)... 

MORI, M., NOMURA, T., OOKA, H., ISHIZAKA, M., YOKOTA, T., SUGIMOTO, K., OKABE, K., KAJIWARA, H., SATOH, K., YAMAMOTO, K., HIROCHIKA, H., KIKUCHI, S., Isolation and characterization of a rice dwarf mutant with a defect in brassinosteroid biosynthesis, Plant Physiol., 2002, 130, 1152-1161. 

CYP85A2, a cytochrome P450, mediates the Baey-er-Villiger oxidation of castasterone to brassinolide in brassinosteroid biosynthesis. Plant Cell 17 2397-2412... 

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