THE PLANT CELL, Vol 5, Issue 3 311-319, Copyright © 1993 by American Society of Plant Biologists
Transposon-Mediated Mutations in the Untranslated Leader of Maize Adh1 that Increase and Decrease Pollen-Specific Gene Expression
R. K. Dawe, A. R. Lachmansingh and M. Freeling
Department of Plant Biology, University of California, Berkeley, California 94720
The unstable mutation Adh1-Fm335 contains a Dissociation (Ds1) transposable
element at position +53 in the untranslated leader of the maize Alcohol
dehydrogenase-1 (Adh1) gene. Excision of Ds1 is known to generate new
alleles with small additions and rearrangements of Adh1 DNA. We
characterized 16 revertant alleles with respect to ADH1 activity levels in
scutellum (nutritive tissue of the seed), anaerobic root, and pollen.
Whereas gene expression was not different from the wild type in the
sporophytic tissues of the scutellum and anaerobic root, there were strong
allelic differences in pollen. One allele underexpressed pollen ADH1 at 48%
of the wild-type level, and another overexpressed pollen ADH1 at 163% of
the wild-type level. Quantitative RNase protection assays demonstrated that
the mutant phenotypes reflected changes in the levels of steady state mRNA
in pollen. These data provide a definitive demonstration of an
overexpression mutant in plants and further show that marked increases in
mRNA levels can follow minor alterations in central untranslated leader
sequences. The nucleotide sequence of 12 new revertant alleles and the
molecular mechanisms responsible for pollen-specific gene expression are
discussed.
