Ag. Mccubbin et al., A MUTANT S-3 RNASE OF PETUNIA-INFLATA LACKING RNASE ACTIVITY HAS AN ALLELE-SPECIFIC DOMINANT-NEGATIVE EFFECT ON SELF-INCOMPATIBILITY INTERACTIONS, The Plant cell, 9(1), 1997, pp. 85-95
Gametophytic self-incompatibility in the Solanaceae is controlled by a
multiallelic locus called the S locus, Growth of pollen tubes in the
pistil is inhibited when the pollen has one of the two S alleles carri
ed by the pistil. The products of a number of pistil S alleles-S prote
ins or S RNases-have been identified, and their role in controlling th
e pistil's ability to reject self-pollen has been positively establish
ed. In contrast, the existence of pollen S allele products has so far
been inferred entirely from genetic evidence. Here, we introduced a mo
dified S-3 gene of Petunia inflata encoding an S-3 RNase lacking RNase
activity into P. inflata plants of the S2S3, genotype to determine wh
ether the production of the mutant protein, designated S-3(H93R), woul
d have any effect on the ability of the transgenic plants to reject S-
2 and S-3 pollen. Analysis of the self-incompatibility behavior of 49
primary transgenic plants and the progeny of three plants (H30, H37, a
nd H40) that produced S-3(H93R) in addition to producing wild-type lev
els of endogenous S-2 and S-3 RNases revealed that S-3(H93R) had a dom
inant negative effect on the function of the S-3 RNase in rejecting se
lf-pollen; however, it had no effect on the function of the S-2 RNase.
One likely explanation of the results is that S-3(H93R) competes with
the S-3 RNase for binding to a common molecule, which is presumably t
he product of the pollen S-3 allele.