title: Identification of the self-incompatibility locus F-box protein-containing complex in Petunia inflata.
abstract: The polymorphic S-locus regulating self-incompatibility (SI) in Petunia contains the S-RNase gene and a number of S-locus F-box (SLF) genes. While penetrating the style through the stigma, a pollen tube takes up all S-RNases, but only self S-RNase inhibits pollen tube growth. Recent evidence suggests that SLFs produced by pollen collectively interact with and detoxify non-self S-RNases, but none can interact with self S-RNase. An SLF may be the F-box protein component of an SCF complex (containing Cullin1, Skp1 and Rbx1), which mediates ubiquitination of protein substrates for degradation by the 26S proteasome. However, the precise nature of the complex is unknown. We used pollen extracts of a transgenic plant over-expressing GFP-fused S2-SLF1 (SLF1 of S 2-haplotype) for co-immunoprecipitation (Co-IP) followed by mass spectrometry (MS). We identified PiCUL1-P (a pollen-specific Cullin1), PiSSK1 (a pollen-specific Skp1-like protein) and PiRBX1 (an Rbx1). To validate the results, we raised transgenic plants over-expressing PiSSK1:FLAG:GFP and used pollen extracts for Co-IP-MS. The results confirmed the presence of PiCUL1-P and PiRBX1 in the complex and identified two different SLFs as the F-box protein component. Thus, all but Rbx1 of the complex may have evolved in SI, and all SLFs may be the F-box component of similar complexes.
authors.affiliation: Intercollege Graduate Degree Program in Plant Biology, Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Shu
authors.initials: S
authors.lastname: Li
authors.forename: Penglin
authors.initials: P
authors.lastname: Sun
authors.forename: Justin Stephen
authors.initials: JS
authors.lastname: Williams
authors.forename: Teh-hui
authors.initials: TH
authors.lastname: Kao
mesh_terms: D001483:Base Sequence; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D017930:Genes, Reporter; D005838:Genotype; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D032306:Petunia / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011058:Pollen / Q000502:physiology; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins; D060436:Self-Incompatibility in Flowering Plants / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D044783:F-Box Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins