S. Hiratsuka et al., Selective inhibition of the growth of incompatible pollen tubes by S-protein in the Japanese pear, SEX PLANT R, 13(4), 2001, pp. 209-215
The S-allele-associated proteins (S-proteins) in the styles of the Japanese
pear (Pyrus serotina Rehd. var. culta Rehd.) were purified by cation excha
nge chromatography. Their inhibitory action on the growth of incompatible p
ollen tubes (pollen tubes bearing the same S-allele as in the style from wh
ich the S-proteins were prepared) was characterized in vitro. Germination a
nd tube growth of self-pollen (pollen from the same cultivar from which the
S-proteins were prepared) decreased dose-dependently when the S-protein wa
s added to the medium. Tube length was reduced to 10% that of compatible po
llen tubes (pollen tubes bearing the S-allele different from that in the st
yle from which the S-proteins were prepared) at 1.5 mug mul(1). S-proteins
from Shinsui (S4S5) also inhibited growth of cross-incompatible Kosui (S4S5
) pollen tubes, but not of compatible Chojuro (S2S3) pollen tubes. After in
activation of RNase of the S-protein, the inhibitory action of the S-protei
n disappeared. These results indicate that the S-protein acts directly to i
nhibit growth of incompatible pollen tubes in Japanese pear styles, and tha
t the RNase activity of the protein is essential for the biological functio
n. However, small amounts of proteins that co-migrated with the S-protein m
ay also play some roles in the inhibition. This is the first report on the
selective inhibitory action of S-proteins in Rosaceae.