PLANT PHYSIOLOGY , Vol 106, Issue 1 25-36, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
The S-Ribonuclease Gene of Petunia hybrida Is Expressed in Nonstylar Tissue, Including Immature Anthers
K. R. Clark and T. L. Sims
Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (K.R.C.)
To determine the ability of isolated S-locus promoter sequences to direct
organ-specific gene expression, we used microprojectile bombardment to
introduce chimeric S-allele/[beta]-glucuronidase genes into different
tissues of Petunia hybrida for transient expression. Histochemical staining
showed that S-locus/[beta]-glucuronidase fusions were expressed in pistil,
ovary, and petal tissue. No expression of the chimeric genes was detected
in leaves or in mature pollen, either by histochemical staining or by
fluorescence assays. RNA blot hybridization confirmed that low levels of
S-locus mRNA accumulate in petals and ovaries in vivo. Analysis of the
expression pattern of S-locus promoter deletions showed that sequences in
the immediate vicinity of the TATA box were sufficient to confer
qualitatively correct organ-specific expression of [beta]-glucuronidase. To
further investigate the potential for S-ribonuclease expression in pollen,
we used the polymerase chain reaction to amplify RNA accumulated in
developing anthers. These assays demonstrated that mRNA for the
S-ribonuclease accumulates to low levels in developing anthers several days
prior to corolla opening and pollen anthesis. We discuss these results in
light of current models of self-incompatibility.
