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Biochem. Soc. Trans. (2006) 34, (1199–1201) (Printed in Great Britain)

Independent Meetings

Dwarfism and cytochrome P450-mediated C-6 oxidation of plant steroid hormones

G. Bishop*1, T. Nomura†, T. Yokota‡, T. Montoya§, J. Castle§, K. Harrison*, T. Kushiro†, Y. Kamiya†, S. Yamaguchi†, S. Bancos, A.-M. Szatmári and M. Szekeres

*Division of Biology, Imperial College London, Wye Campus, Kent TN25 5AH, U.K., †Plant Science Center, RIKEN, Institute of Physical and Chemical Research, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan, ‡Department of Biosciences, Teikyo University, Utsunomiya 320-8551, Japan, §Institute of Biological Sciences, University of Wales, Aberystwyth SY23 3DD, U.K., and Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary

Key words: Arabidopsis, brassinolide, brassinosteroid, cytochrome P450, dwarfism, plant steroid hormone.

Abbreviations used: BL, brassinolide; BR, brassinosteroid; BR1, brassinosteroid-insensitive 1; CS, castasterone; CYP, cytochrome P450; 6-deoxoCS, 6-deoxocastasterone.

¹To whom correspondence should be addressed (email g.bishop@imperial.ac.uk).

Abstract

BRs (brassinosteroids) are plant steroid hormones that are essential for normal plant development. The dramatic dwarfism exhibited by mutants in the CYP (cytochrome P450) enzymes involved in BR biosynthesis indicates a role for these hormones in plant growth and development. Since the mid-1990s, collaborative research has been geared towards developing a better understanding of the CYP85 class of CYPs involved in BR biosynthesis in both Arabidopsis and tomato. Some of the most recent observations include the fact that certain CYP85 CYPs catalyse the synthesis of the most bioactive BR, BL (brassinolide). Current evidence suggests that evolution of this function may have occurred independently in different dicotyledonous species. Interestingly, BL accumulates in tomato fruits, highlighting a key role for this hormone in fruit development. At the same time as developing a better understanding of the enzymatic function of these CYPs, we have also carried out experiments towards characterizing where and when these genes are expressed and mechanisms of their regulation. As expected for a hormone involved in growth and development, biosynthetic gene promoter activity is associated with young rapidly growing cells and with fruit development.

Received 21 June 2006

© 2006 Biochemical Society