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First published online July 22, 2005; 10.1104/pp.105.061598 Plant Physiology 138:2033-2047 (2005) © 2005 American Society of Plant Biologists Arabidopsis cyp51 Mutant Shows Postembryonic Seedling Lethality Associated with Lack of Membrane Integrity1,[w]Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151–747, Korea (H.B.K., M.K., S.C., C.S.A.); Institut de Biologie Moléculaire des Plantes/Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Strasbourg cedex, F–67083, France (H.S., F.D.); Environmental Biotechnology Research Center, Gyeongsang National University, Chinju 660–701, Korea (C.-H.G.); Ceres, Inc., Thousand Oaks, California 91320 (K.A.F.); and Institut National de la Recherche Agronomique, Centre de Recherches de Sophia Antipolis, Unité Mixte de Recherche 1112, 06903 Sophia Antipolis, France (R.F.)
CYP51 exists in all organisms that synthesize sterols de novo. Plant CYP51 encodes an obtusifoliol 14
1 This work was supported by the Human Frontier Science Program (grant no. RG0280/1999–M), in part by the Korea Science and Engineering Foundation (grant no. R01–2001–000–00104–0 to C.S.A.), in part by a grant from the Environmental Biotechnology National Core Research Center, Gyeongsang National University (to C.-H.G.), in part by a grant from the Plant Metabolism Research Center at Kyung Hee University (Science Research Center Program from the Korea Science and Engineering Foundation to S.C.), and by the BK21 Research Program from the Korean Ministry of Education and Human Resources Development (to H.B.K.). [w] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.061598. * Corresponding author; e-mail hobang{at}snu.ac.kr; fax 82–2–872–1993. Received February 17, 2005; returned for revision May 10, 2005; accepted May 10, 2005. This article has been cited by other articles:
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-demethylase involved in the postsqualene sterol biosynthetic pathway. According to the current gene annotation, the Arabidopsis (Arabidopsis thaliana) genome contains two putative CYP51 genes, CYP51A1 and CYP51A2. Our studies revealed that CYP51A1 should be considered an expressed pseudogene. To study the functional importance of the CYP51A2 gene in plant growth and development, we isolated T-DNA knockout alleles for CYP51A2. Loss-of-function mutants for CYP51A2 showed multiple defects, such as stunted hypocotyls, short roots, reduced cell elongation, and seedling lethality. In contrast to other sterol mutants, such as fk/hydra2 and hydra1, the cyp51A2 mutant has only minor defects in early embryogenesis. Measurements of endogenous sterol levels in the cyp51A2 mutant revealed that it accumulates obtusifoliol, the substrate of CYP51, and a high proportion of 14
8-sterols, at the expense of campesterol and sitosterol. The cyp51A2 mutants have defects in membrane integrity and hypocotyl elongation. The defect in hypocotyl elongation was not rescued by the exogenous application of brassinolide, although the brassinosteroid-signaling cascade is apparently not affected in the mutants. Developmental defects in the cyp51A2 mutant were completely rescued by the ectopic expression of CYP51A2. Taken together, our results demonstrate that the Arabidopsis CYP51A2 gene encodes a functional obtusifoliol 14
