Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 95pg1
GENETIC AND MOLECULAR ANALYSIS OF EMP2 AND DSC1: TWO NOVEL
MAIZE GENES FUNCTIONING IN KERNEL DEVELOPMENT.
*Michael J. Scanlon, #Philip S. Stinard, #Donald S. Robertson
and *Alan M. Myers, *Department of Biochemistry and
Biophysics, Department of Zoology and Genetics, Iowa State
University, Ames, IA 5001 1.
A transposon tagging experiment using the Robertson's
Mutator (Mu) maize transposable element system has generated over
100 recessive mutations causing various defects in kernel
development. Among these were two novel defective kernel (dek)
mutants, empty pericarp 2 (emp2) and discolored 1 (dsc1). The
emp2 mutation causes an empty pericarp, germless phenotype that
is homozygous lethal. Classical genetic techniques were used to
place emp2 to chromosome 2L, approximately 18.5 cM proximal to
w3. emp2 mutant kernels are first distinguishable from wild type
sibling kernels 14 days after pollination (DAP). Embryos
homozygous for emp2 are developmentally arrested, and cannot be
rescued on enriched tissue culture medium. A genomic DNA
fragment corresponding to the mutation emp2 was obtained through
phage lambda cloning of a Mu transposon-tagged restriction
fragment. Maize genomic DNA flanking the Mu insertion in the
emp2 clone was used as a probe in Northern hybridization analyses
to identify an RNA that is expressed in developing kernels.
Efforts are now underway to isolate an Emp2 cDNA clone from a 14
DAP cDNA library. A similar approach was used to clone a Mu-
tagged restriction fragment corresponding to the novel kernel
mutation dsc1. This lethal mutation causes a discolored,
germless seed and was mapped to approximately 4 cM from su1.
dsc1 mutants are first distinguishable at 8 DAP, and mutant
embryos are developmentally retarded. Embryos dissected from 20
DAP dsc1 kernels germinate on enriched tissue culture medium,
producing a seedling that dies at the single leaf stage. A
genomic DNA fragment flanking the Mu1 insertion in the dsc1 clone
was used as a probe in Northern analyses to identify a kernel
specific transcript that is expressed 6 through 9 days after
pollination. A 7 DAP kernel library is being screened to isolate
a Dsc1 DNA clone.
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