Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
SUMMARY Self‐incompatibility in
Petunia is controlled by the polymorphicS ‐locus, which containsS‐RNase encoding the pistil determinant and 16–20S‐locus F‐box (SLF ) genes collectively encoding the pollen determinant. Here we sequenced and assembled approximately 3.1 Mb of theS2 ‐haplotype of theS ‐locus inPetunia inflata using bacterial artificial chromosome clones collectively containing all 17SLF genes,SLFLike1 , andS‐RNase . TwoSLF pseudogenes and 28 potential protein‐coding genes were identified, 20 of which were also found at theS ‐loci of both theS6a ‐haplotype ofP. inflata and theSN ‐haplotype of self‐compatiblePetunia axillaris , but not in theS ‐locus remnants of self‐compatible potato (Solanum tuberosum ) and tomato (Solanum lycopersicum ). Comparative analyses ofS ‐locus sequences of these threeS ‐haplotypes revealed potential genetic exchange in the flanking regions ofSLF genes, resulting in highly similar flanking regions between different types ofSLF and between alleles of the same type ofSLF of differentS ‐haplotypes. The high degree of sequence similarity in the flanking regions could often be explained by the presence of similar long terminal repeat retroelements, which were enriched at theS ‐loci of all threeS ‐haplotypes and in the flanking regions of allS ‐locus genes examined. We also found evidence of the association of transposable elements withSLF pseudogenes. Based on the hypothesis thatSLF genes were derived by retrotransposition, we identified 10F‐box genes as putativeSLF parent genes. Our results shed light on the importance of non‐coding sequences in the evolution of theS ‐locus, and on possible evolutionary mechanisms of generation, proliferation, and deletion ofSLF genes. -
Summary The collaborative non‐self‐recognition model for S‐
RN ase‐based self‐incompatibility predicts that multiple S‐locus F‐box proteins (SLF s) produced by pollen of a givenS ‐haplotype collectively mediate ubiquitination and degradation of all non‐self S‐RN ases, but not self S‐RN ases, in the pollen tube, thereby resulting in cross‐compatible pollination but self‐incompatible pollination. We had previously used pollen extracts containingGFP ‐fused S2‐SLF 1 (SLF 1 with anS 2‐haplotype) ofPetunia inflata for co‐immunoprecipitation (Co‐IP ) and mass spectrometry (MS ), and identified PiCUL 1‐P (a pollen‐specific Cullin1), PiSSK 1 (a pollen‐specific Skp1‐like protein) and PiRBX 1 (a conventional Rbx1) as components of theSCFS 2–SLF 1complex. Using pollen extracts containing PiSSK 1:FLAG :GFP for Co‐IP /MS , we identified two additionalSLF s (SLF 4 andSLF 13) that were assembled intoSCFSLF complexes. As 17 genes (SLF toSLF 1 ) have been identified inSLF 17S 2andS 3pollen, here we examined whether all 17SLF s are assembled into similar complexes and, if so, whether these complexes are unique toSLF s. We modified the previous Co‐IP /MS procedure, including the addition of style extracts from four differentS ‐genotypes to pollen extracts containing PiSSK 1:FLAG :GFP , to perform four separate experiments. The results taken together show that all 17SLF s and anSLF ‐like protein,SLFL ike1 (encoded by anS ‐locus‐linked gene), co‐immunoprecipitated with PiSSK 1:FLAG :GFP . Moreover, of the 179 other F‐box proteins predicted byS 2andS 3pollen transcriptomes, only a pair with 94.9% identity and another pair with 99.7% identity co‐immunoprecipitated with PiSSK 1:FLAG :GFP . These results suggest thatSCFSLF complexes have evolved specifically to function in self‐incompatibility.