A different function for a member of an ancient and highly conserved cytochrome P450 family: From essential sterols to plant defense

Xiaoquan Qi, Saleha Bakht, Bo Qin, J. Michael Leggett, Andrew Hemmings, Fred Mellon, John Eagles, Daniele Werck-Reichhart, Hubert Schaller, Agnes Lesot, Rachel Melton, Anne Osbourn

Research output: Contribution to journalArticlepeer-review

160 Citations (SciVal)

Abstract

CYP51 sterol demethylases are the only cytochrome P450 enzymes with a conserved function across the animal, fungal, and plant kingdoms (in the synthesis of essential sterols). These highly conserved enzymes, which are important targets for cholesterol-lowering drugs, antifungal agents, and herbicides, are regarded as the most ancient member cytochrome P450 family. Here we present a report of a CYP51 enzyme that has acquired a different function. We show that the plant enzyme AsCYP51H10 is dispensable for synthesis of essential sterols and has been recruited for the production of antimicrobial compounds (avenacins) that confer disease resistance in oats. The AsCyp51H10 gene is synonymous with Sad2, a gene that we previously had defined by mutation as being required for avenacin synthesis. In earlier work, we showed that Sad1, the gene encoding the first committed enzyme in the avenacin pathway (β-amyrin synthase), had arisen by duplication and divergence of a cycloartenol synthase-like gene. Together these data indicate an intimate evolutionary connection between the sterol and avenacin pathways. Sad1 and Sad2 lie within 70 kb of each other and are expressed specifically in the epidermal cells of the root tip, the site of accumulation of avenacins. These findings raise intriguing questions about the recruitment, coevolution, and regulation of the components of this specialized defense-related metabolic pathway.
Original languageEnglish
Pages (from-to)18848-18853
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number49
DOIs
Publication statusPublished - 2006
Externally publishedYes

Keywords

  • Avena
  • disease resistance
  • oat
  • metabolic diversity
  • gene duplication

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