| Summary: | Self-incompatibility is a widespread genetic mechanism found in flowering plants. It plays a crucial role in preventing inbreeding and promoting outcrossing. The genes that control self-incompatibility in plants are typically determined by the S-locus female determinant factor and the S-locus male determinant factor. In the Solanaceae family, the male determinant factor is often the <i>SLF</i> gene. In this research, we cloned and analyzed 13 <i>S<sub>2</sub>-LbSLF</i> genes from the <i>L. barbarum</i> genome, which are located on chromosome 2 and close to the physical location of the S-locus female determinant factor S-RNase, covering a region of approximately 90.4 Mb. The amino acid sequence identity of the 13 <i>S<sub>2</sub>-LbSLFs</i> is 58.46%, and they all possess relatively conserved motifs and typical <i>F-box</i> domains, without introns. A co-linearity analysis revealed that there are no tandemly repeated genes in the <i>S<sub>2</sub>-LbSLF</i> genes, and that there are two pairs of co-linear genes between <i>S<sub>2</sub>-LbSLF</i> and the tomato, which also belongs to the Solanaceae family. A phylogenetic analysis indicates that the <i>S<sub>2</sub>-LbSLF</i> members can be divided into six groups, and it was found that the 13 <i>S<sub>2</sub>-LbSLFs</i> are clustered with the <i>SLF</i> genes of tobacco and <i>Petunia inflata</i> to varying degrees, potentially serving as pollen determinant factors regulating self-incompatibility in <i>L. barbarum</i>. The results for the gene expression patterns suggest that <i>S<sub>2</sub>-LbSLF</i> is only expressed in pollen tissue. The results of the yeast two-hybrid assay showed that the C-terminal region of <i>S<sub>2</sub>-LbSLFs</i> lacking the <i>F-box</i> domain can interact with S-RNase. This study provides theoretical data for further investigation into the functions of <i>S<sub>2</sub>-LbSLF</i> members, particularly for the identification of pollen determinant factors regulating self-incompatibility in <i>L. barbarum</i>.
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