Gametophytic Self-Incompatibility is a reproductive strategy to prevent inbreeding and promote outcrossing, and it is controlled by the self-incompatibility locus (S-locus). Studies to understand molecular and evolutionary aspects of the SI system in the Solanaceae have been conducted using several genera, including Petunia, Nicotiana, and Solanum. S-RNases are pistil determinants of gametophytic SI, and multiple S-RNase alleles have been identified in a few potato species. SLFs, the pollen determinants of SI, are linked to S-RNases on chromosome 1. The S-RNase and SLFs present on each chromatid determine an individual’s self-compatible (SC) or self-incompatible (SI) haplotypes. We used long-read genome sequencing and RNA sequencing from styles and pollen to assess the diversity and composition of elements within the S-locus. RNA for RNA-seq was collected from stylar tissue and germinated pollen. For three genotypes, PacBio Iso-Sequencing was used to confirm the presence of alternative transcripts for the S-RNase gene. The combined datasets enabled us to localize both the male (pollen) and female (stylar) components of the S-locus. Sequences of the identified S-RNases and SLFs were used to evaluate their phylogenies along with other Solanaceae sequences for the same genes obtained from databases. Our analysis showed that SLF sequences are expressed in pollen but not in styles, vary in number between individuals, and are distributed across a 9-17 Mb region flanking one S-RNase gene. Preferential associations within haplotigs of specific S-RNase types and SLF types were not observed. Extensive sequence diversity was observed for S-RNases and SLFs, and phylogenetic analysis indicates that diversification of both genes predates the divergence between tomatoes and potatoes.
Data from: The structure and allelic diversity of the self-incompatibility locus (S-locus) in diploid potatoes inferred from genome sequences and transcriptome data from styles and pollen
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