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Abstract

The endogenous brassinosteroids in the dwarf mutant lk of pea (Pisum sativum) were quantified by gas chromatographyselected
ion monitoring. The levels of castasterone, 6-deoxocastasterone, and 6-deoxotyphasterol in lk shoots were reduced
4-, 70-, and 6-fold, respectively, compared with those of the wild type. The fact that the application of brassinolide restored
the growth of the mutant indicated that the dwarf mutant lk is brassinosteroid deficient. Gas chromatography-selected ion
monitoring analysis of the endogenous sterols in lk shoots revealed that the levels of campestanol and sitostanol were reduced
160- and 10-fold, respectively, compared with those of wild-type plants. These data, along with metabolic studies, showed that
the lk mutant has a defect in the conversion of campest-4-en-3-one to 5a-campestan-3-one, which is a key hydrogenation step in
the synthesis of campestanol from campesterol. This defect is the same as that found in the Arabidopsis det2 mutant and the
Ipomoea nil kbt mutant. The pea gene homologous to the DET2 gene, PsDET2, was cloned, and it was found that the lk mutation
would result in a putative truncated PsDET2 protein. Thus it was concluded that the short stature of the lk mutant is due to
a defect in the steroidal 5a-reductase gene. This defect was also observed in the callus induced from the lk mutant. Biosynthetic
pathways involved in the conversion of campesterol to campestanol are discussed in detail.

Item Type:	Article
Authors/Creators:	Nomura, T and Jager, CE and Kitasaka, Y and Takeuchi, K and Fukami, M and Yoneyama, K and Matsushita, Y and Nyunoya, H and Takatsuto, S and Fujioka, S and Smith, JJ and Kerckhoffs, LHJ and Reid, JB and Yokota, T
Journal or Publication Title:	Plant Physiology
ISSN:	0032-0889
DOI / ID Number:	10.​1104/​pp.​104.​043786
Additional Information:	Copyright © 2004 American Society of Plant Biologists
Item Statistics:	View statistics for this item

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