Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: TRANSPOSON TAGGING, ISOLATION AND CHARACTERIZATION OF A NUCLEAR
MALE FERTILITY GENE FROM MAIZE
TRANSPOSON TAGGING, ISOLATION AND CHARACTERIZATION OF A NUCLEAR
MALE FERTILITY GENE FROM MAIZE.
Tim W. Fox, Mary R. Trimnell and Marc C. Albertsen, Department of
Biotechnology, Pioneer Hi-Bred International, Inc. Johnston, IA
50131
Genetic male sterility can result from a mutation in one of
many genes involved in microsporogenesis. These genes are
collectively referred to as male fertility genes. In maize, over
20 genetic loci have been identified as being essential for male
fertility. Cytological studies of sterile mutants for many of
these fertility loci indicate that microspore breakdown is
diverse in timing as well as its effect on microspore morphology
[M. C. Albertsen and R. L. Phillips, Can. J. Genet. Cytol.,
21:195 (1981)]. This suggests that microsporogenesis is a
complex process, controlled by more than one mechanism. Despite
the number of male sterile mutants described in maize, little
progress has been made in characterizing genes responsible for
male fertility. Most male sterility research has been
descriptive. Recently, we used the transposable element
Activator (Ac) to tag a gene responsible for male fertility in
Zea mays. This Ac induced mutation inhibits wall formation in
developing microspores. The genomic DNA flanking the Ac element
from the mutant was amplified using inverse-PCR. The amplified
fragment was used to screen a cDNA library constructed from maize
tassel MRNA. A putative full length cDNA (1.4Kb) was isolated.
Northern analysis indicates the transcript is only present in
tassels of fertile plants. The cDNA sequence contains a 1342
base pair open reading frame coding for a deduced polypeptide of
414 amino acid residues. To demonstrate gene function, plants
were screened for Ac transposition from the mutant allele. A
revertant allele was identified that contains a 6 base pair Ac
footprint which restores the reading frame of the gene as well as
restoring male fertility to the plant. The deduced polypeptide
was compared to the Genbank Protein database. Homology (34%
identity over 236 amino acids) was found to strictosidine
synthase, an enzyme involved in the formation of strictosidine, a
key intermediate in indole-type alkaloid production. This male
fertility gene has been designated Ms45.
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