THE PLANT CELL, Vol 1, Issue 7 727-736, Copyright © 1989 by American Society of Plant Biologists
Gametophytic and Sporophytic Expression of Anther-Specific Genes in Developing Tomato Anthers
V. M. Ursin, J. Yamaguchi and S. McCormick
United States Department of Agriculture/Agricultural Research Service, Plant Gene Expression Center, 800 Buchanan Street, Albany, California 94710
The tissue localization of transcripts corresponding to five
anther-specific cDNA clones isolated from tomato was determined.
Transcripts specified by three of the cDNA clones were first detectable in
anthers containing mitotic-stage gametophytes and were localized to the
gametophyte. Transcripts specified by the two other cDNA clones were not
detectable until anthers had reached a later developmental stage; these
transcripts were also localized to the (now bicellular) gametophytes.
Transcript levels for all of the cDNAs increased during gametogenesis and
reached maximal levels in mature pollen grains. These mRNAs persisted in in
vitro-grown pollen tubes, concentrating toward the tips of the growing
tubes. At flower maturity, transcripts specified by each of the cDNAs were
also detected in the epidermal and endothecial cell layers of the anther
wall. The spatial distribution of transcripts in the anther wall was
confined to that region of the anther that surrounds the locule.
Transcripts were not detected in the sterile tip of the anther or in the
filament. mRNA levels for these cDNA clones were markedly reduced in the
anthers of several independent male-sterile mutants of tomato. Our results
provide evidence that these anther-specific cDNAs represent genes expressed
in both the gametophytic and sporophytic phases of the plant life cycle.
The patterns of mRNA accumulation observed support the hypothesis that the
proteins encoded by these genes function during pollen development and
pollen tube growth.
