Petunia integrifolia subsp. inflata Variation

Angiosperms such as Petunia possesses self-incompatibility, by which pistils reject self-pollen but accept non-self pollen for fertilization. The male and female determinant genes that regulate self/non-self recognition between pollen and pistil are located at the highly polymorphic S-locus. An S-haplotype contains multiple male determinant pollen-specific S-locus F-box (SLF) genes and a single female determinant pistil-specific S-RNase gene. To date, 10 different types of SLF genes have been identified, however the total number of SLF genes involved in SI remains unknown. Using a next generation RNA-seq approach in conjunction with Trinity de novo transcript assembly, we have characterized the Petunia pollen transcriptomes of both the S2-haplotype and S3-haplotype to identify most, if not all, SLF genes in their respective S-loci. We also analyzed the transcriptome of Petunia S3S3 leaf as a means to filter out non-pollen specific genes. To identify potential SLF genes, we used criteria from known SLF genes such as sequence similarity, pollen gene expression in comparison to gene expression in leaf, the presence of multiple alleles, S-locus linkage, and placement in a monophyletic clade with all other known Petunia SLF sequences. From this data, we found 7 additional SLF genes in both the S2-locus and S3-locus, bringing the total number of SLF genes to 17. This transcriptome data is not only useful in terms of SLF gene discovery, and holds promise for future analyses.