1. Evolutionary history of two pollen self‐incompatibility factors reveals alternate routes to self‐compatibility within Solanum
- Author
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Dragomira N. Markova, Jennifer J. Petersen, Wentao Li, Roger T. Chetelat, Matthew J. Valle, Adryanna Corral, and Sarah E. Yam
- Subjects
0301 basic medicine ,Genetics ,Gynoecium ,Phylogenetic tree ,biology ,Solanum arcanum ,food and beverages ,Plant Science ,Solanum ,medicine.disease_cause ,biology.organism_classification ,Biological Evolution ,Complementation ,03 medical and health sciences ,030104 developmental biology ,Pollen ,medicine ,Allele ,Pollination ,Inbreeding ,Ecology, Evolution, Behavior and Systematics ,Demography - Abstract
Premise of the study Self-incompatibility (SI) prevents self-fertilization and reduces inbreeding. While SI is common in plants, transitions to self-compatibility (SC) occur frequently. Little is known about the genetic changes and evolutionary steps underlying these shifts. Methods In the Solanaceae, SI is gametophytic, with specificity determined by S-RNases in the pistil and S-locus F-box proteins (SLFs) in pollen. We examined the role of two pollen factors, Cullin1 (CUL1) and SLF-23, in SI → SC transitions in wild tomato species from the Arcanum species group (Solanum arcanum, S. neorickii, and S. chmielewskii). Pollen compatibility was assessed on tester lines that reject pollen lacking functional SLF-23 or CUL1. Complementation tests, gene sequencing, and phylogenetic analyses were used to characterize both functional and nonfunctional alleles. Key results We found evidence for multiple independent SI → SC transitions. In S. arcanum and S. chmielewskii, SC is caused by loss of pistil S-RNase activity, while in S. neorickii SC is associated with expression of a functional SLF-23 that recognizes the S9 type S-RNase expressed in its pistils. Interestingly, we found identical deletion mutations in CUL1 exon 7 of S. chmielewskii as previously seen in S. habrochaites. Conclusions Mating system transitions in the Arcanum group have occurred via both pistil loss-of-function and pollen gain-of-function SC mutations. Mutations common to S. chmielewskii and S. habrochaites must have arisen in a common ancestor, possibly to the entire tomato clade, then became fixed in different lineages after loss of pistil-side SI function.
- Published
- 2017