K. Wilson et al., A DISSOCIATION INSERTION CAUSES A SEMIDOMINANT MUTATION THAT INCREASES EXPRESSION OF TINY, AN ARABIDOPSIS GENE-RELATED TO APETALA2, The Plant cell, 8(4), 1996, pp. 659-671
A novel transposon-tagging strategy designed to recover dominant gain-
of-function alleles was performed with Arabidopsis by using a Dissocia
tion element with a cauliflower mosaic virus 35S promoter transcribing
outward over one terminus. Lines containing transposed copies of this
transposon were screened for mutants, and a semidominant mutation aff
ecting plant height, hypocotyl elongation, and fertility was recovered
. The pleiotropic effects of this mutation appear to result from a gen
eral reduction in cell expansion, and some of the effects are similar
to those caused by supplying exogenous ethylene or cytokinin to wild-t
ype seedlings. In addition, the arrangement of cells in some organs, s
uch as the etiolated hypocotyl, is disorganized, The mutation was call
ed tiny, and the affected gene was cloned by first using transposon se
quences to isolate the mutant allele. The predicted protein product of
the TINY gene shows strong homology with the DNA binding domain of a
recently identified class of plant transcription factors. This domain,
called the APETALA2 domain, was initially identified as a duplicated
region within the APETALA2 gene of Arabidopsis and then as a conserved
region between APETALA2 and the ethylene responsive element binding p
roteins of tobacco. In the mutant allele, the Dissociation element is
inserted in the untranslated leader of the TINY gene, 35 bp from the A
TG, and the mutant contains a novel transcript that initiates from the
cauliflower mosaic virus 35S promoter within the transposon. This tra
nscript is present in greater abundance than the wild-type TINY transc
ript; therefore, the semidominant tiny mutation most likely results fr
om increased, or ectopic, expression of the gene.