Plant Physiology 93:1168-1174 (1990)
© 1990 American Society of Plant Biologists
Development and Growth Regulation
A Mutant Gene That Increases Gibberellin Production in Brassica1
Stewart B. Rood,
Paul H. Williams,
David Pearce,
Noboru Murofushi,
Lewis N. Mander and
Richard P. Pharis
Department of Biological Sciences, University of Lethbridge, Alberta, T1K 3M4, Canada,
Department of Plant Pathology, University of Wisconsin-Madison, Wisconsin 53706,
Plant Physiology Research Group, Department of Biological Sciences, University of Calgary, Alberta, T2N 1N4, Canada,
Department of Agricultural Chemistry, The University of Tokyo, Bunkyo-Ku, Tokyo,
Research School of Chemistry, Australian National University, Canberra, A.C.T. 2600, Australia
A single gene mutant (elongated internode [ein/ein]) with accelerated shoot elongation was identified from a rapid cycling line of Brassica rapa. Relative to normal plants, mutant plants had slightly accelerated floral development, greater stem dry weights, and particularly, increased internode and inflorescence elongation. The application of the triazole plant growth retardant, paclobutrazol, inhibited shoot elongation, returning ein to a more normal phenotype. Conversely, exogenous gibberellin A3 (GA3) can convert normal genotypes to a phenotype resembling ein. The content of endogenous GA1 and GA3 were estimated by gas chromatography-selected ion monitoring using [2H]GA1, as a quantitative internal standard and at day 14 were 1.5- and 12.1-fold higher per stem, respectively, in ein than in normal plants, although GA concentrations were more similar. The endogenous levels of GA20 and GA1, and the rate of GA19 metabolism were simultaneously analyzed at day 7 by feeding [2H2]GA19 and measuring metabolites [2H2]GA20 and [2H2]GA1 and endogenous GA20 and GA1, with [2H5]GA20 and [2H5]GA1 as quantitative internal standards. Levels of GA1 and GA20 were 4.6- and 12.9-fold higher, respectively, and conversions to GA20 and GA1 were 8.3 and 1.3 times faster in ein than normal plants. Confirming the enhanced rate of GA1 biosynthesis in ein, the conversion of [3H]GA20 to [3H]GA1 was also faster in ein than in the normal genotype. Thus, the ein allele results in accelerated GA1 biosynthesis and an elevated content of endogenous GAs, including the dihydroxylated GAs A1 and A3. The enhanced GA production probably underlies the accelerated shoot growth and development, and particularly, the increased shoot elongation.
1 Supported through Natural Sciences and Engineering Research Council of Canada (NSERCC) grants UO286, A-2585, and 24990 to S. B. R. and R. P. P.
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