title: AhSSK1, a novel SKP1-like protein that interacts with the S-locus F-box protein SLF.
abstract: The S-locus F-box (SLF/SFB) protein, recently identified as the pollen determinant of S-RNase-based self-incompatibility (SI) in Solanaceae, Scrophulariaceae and Rosaceae, has been proposed to serve as the subunit of an SCF (SKP1-CUL1-F-box) ubiquitin ligase and to target its pistil counterpart S-RNase during the SI response. However, the underlying mechanism is still in dispute, and the putative SLF-binding SKP1-equivalent protein remains unknown. Here, we report the identification of AhSSK1, Antirrhinum hispanicumSLF-interacting SKP1-like1, using a yeast two-hybrid screen against a pollen cDNA library. GST pull-down assays confirmed the SSK1-SLF interaction, and showed that AhSSK1 could connect AhSLF to a CUL1-like protein. AhSSK1, despite having a similar secondary structure to other SKP1-like proteins, appeared quite distinctive in sequence and unique in a phylogenetic analysis, in which no SSK1 ortholog could be predicted in the sequenced genomes of Arabidopsis and rice. Thus, our results suggest that the pollen-specific SSK1 could be recruited exclusively as the adaptor of putative SCF(SLF) in those plants with S-RNase-based SI, providing an important clue to dissecting the function of the pollen determinant.
authors.affiliation: Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences and National Center for Plant Gene Research, Beijing 100080, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Huang
authors.forename: Lan
authors.initials: L
authors.lastname: Zhao
authors.forename: Qiuying
authors.initials: Q
authors.lastname: Yang
authors.forename: Yongbiao
authors.initials: Y
authors.lastname: Xue
mesh_terms: D017398:Alternative Splicing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D032161:Antirrhinum / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000378:metabolism*; D018745:Genome, Plant; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011058:Pollen / Q000166:cytology / Q000378:metabolism; D025941:Protein Interaction Mapping; D044786:S-Phase Kinase-Associated Proteins / Q000378:metabolism*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D020798:Two-Hybrid System Techniques
chemical_list: D044783:F-Box Proteins; D010940:Plant Proteins; D044786:S-Phase Kinase-Associated Proteins