Abstract
As an allo-recognition mechanisms to prevent self-fertilization, Solanaceae plants share S-RNase-type self-incompatibility (SI) systems, in which S-RNases and SLFs (S-locus F-box) have been identified as S-haplotype determinants of the pistil and the pollen, respectively. However, only one SLF gene, PiSLF2 in Petunia inflata, has been demonstrated to be the pollen determinant by transgenic experiment, and little is known about molecular details of self/non-self recognition mechanisms. In order to characterize the S-haplotype specific interactions between S-RNases and SLFs, we isolated new SLF alleles from Petunia hybrida.
We show that transformation of SB2SD2 plants with one of the new SLF alleles, SD2SLF, causes breakdown of pollen SI function. This breakdown is consistent with 'competitive interaction' phenomenon, which explains the SI-breakdown observed in tetraploid plants, and therefore supports that SD2SLF is a pollen determinant. The in vitro protein binding assays show the non-self specific interaction between SB2-RNase and SD2SLF. These results support the model in which SLFs are able to recognize and inactivate the non-self S-RNase, but not the self S-RNase.
