THE PLANT CELL, Vol 5, Issue 12 1771-1782, Copyright © 1993 by American Society of Plant Biologists
S-RNase Gene of Nicotiana alata Is Expressed in Developing Pollen
P. N. Dodds, I. Bonig, H. Du, J. Rodin, M. A. Anderson, E. Newbigin and A. E. Clarke
Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville, Victoria 3052, Australia
In the solanaceous plant Nicotiana alata, self-incompatibility is
controlled by a single, multiallelic locus (S locus) expressed in both
pollen and pistil. Previously, we have shown cosegregation between alleles
of the S locus and alleles of a gene that encodes a glycoprotein with
ribonuclease activity (S-RNase). Furthermore, expression of the S-RNase
gene is apparently confined to the pistil and is correlated with the onset
of self-incompatibility. In this paper, we report that the S-RNase gene is
also expressed at low levels in developing pollen. A transcript in
developing pollen hybridized to a cDNA encoding the S2-RNase allele of the
parent plant and did not hybridize to cDNAs encoding other S-RNase alleles.
Two cDNAs for the S2-RNase were cloned from a library derived from anthers
of a plant homozygous for the S2 allele and both corresponded to the coding
sequence of the S2-RNase. The product of the S-RNase gene was detected by
immunocytochemistry in the intine of mature, hydrated pollen grains. These
results are interpreted in the light of current knowledge of the structure
of the S locus.
