PLANT PHYSIOLOGY , Vol 115, Issue 3 1009-1020, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Characterization of New Gibberellin-Responsive Semidwarf Mutants of Arabidopsis
V. M. Sponsel, F. W. Schmidt, S. G. Porter, M. Nakayama, S. Kohlstruk and M. Estelle
Division of Life Sciences, University of Texas at San Antonio, San Antonio, Texas 78249 (V.M.S., S.G.P., M.N.)
Chemical mutagenesis of Arabidopsis thaliana (L.) Heynh. yielded four
semidwarf mutants, all of which appeared to be gibberellin
(GA)-biosynthesis mutants. All four had atypical response profiles to
C20-GAs, suggesting that each had impaired 20-oxidation. One mutant, 11.2,
was shown to be allelic to ga5 and has been named ga5-2. It had altered
metabolism of [14C]GA15 relative to that in wild-type plants and
undetectable levels of C19-GAs in young stems, consistent with the known
function of GA5 as a stem-expressed GA 20-oxidase. Two mutants (2.1 and
10.3), which had very short inflorescences and siliques, were allelic to
each other but not to the known GA-responding mutants, ga1 to ga5. The
locus defined by these two mutations is provisionally named GA6 and is
purported to encode an inflorescence- and silique-expressed GA 20-oxidase.
A double mutant, ga5-2 ga6-2, had an extreme dwarf phenotype with very
short siliques. The fourth mutation, 1.1, gave a phenotype like ga5, but
was not allelic to any of the known ga mutations. It has not yet been given
a gene symbol pending further studies.
