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Title: All 17 S‐locus F‐box proteins of the S 2 ‐ and S 3 ‐haplotypes of Petunia inflata are assembled into similar SCF complexes with a specific function in self‐incompatibility

The collaborative non‐self‐recognition model for S‐RNase‐based self‐incompatibility predicts that multiple S‐locus F‐box proteins (SLFs) produced by pollen of a givenS‐haplotype collectively mediate ubiquitination and degradation of all non‐self S‐RNases, but not self S‐RNases, in the pollen tube, thereby resulting in cross‐compatible pollination but self‐incompatible pollination. We had previously used pollen extracts containingGFP‐fused S2SLF1 (SLF1 with anS2‐haplotype) ofPetunia inflatafor co‐immunoprecipitation (Co‐IP) and mass spectrometry (MS), and identified PiCUL1‐P (a pollen‐specific Cullin1), PiSSK1 (a pollen‐specific Skp1‐like protein) and PiRBX1 (a conventional Rbx1) as components of theSCFS2–SLF1complex. Using pollen extracts containing PiSSK1:FLAG:GFPfor Co‐IP/MS, we identified two additionalSLFs (SLF4 andSLF13) that were assembled intoSCFSLFcomplexes. As 17SLFgenes (SLF1toSLF17) have been identified inS2andS3pollen, here we examined whether all 17SLFs are assembled into similar complexes and, if so, whether these complexes are unique toSLFs. We modified the previous Co‐IP/MSprocedure, including the addition of style extracts from four differentS‐genotypes to pollen extracts containing PiSSK1:FLAG:GFP, to perform four separate experiments. The results taken together show that all 17SLFs and anSLF‐like protein,SLFLike1 (encoded more » by anS‐locus‐linked gene), co‐immunoprecipitated with PiSSK1:FLAG:GFP. Moreover, of the 179 other F‐box proteins predicted byS2andS3pollen transcriptomes, only a pair with 94.9% identity and another pair with 99.7% identity co‐immunoprecipitated with PiSSK1:FLAG:GFP. These results suggest thatSCFSLFcomplexes have evolved specifically to function in self‐incompatibility.

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Publication Date:
Journal Name:
The Plant Journal
Page Range or eLocation-ID:
p. 606-616
Sponsoring Org:
National Science Foundation
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