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Multiple features that distinguish unilateral incongruity and self-incompatibility in the tomato clade.

TitleMultiple features that distinguish unilateral incongruity and self-incompatibility in the tomato clade.
Publication TypeJournal Article
Year of Publication2010
AuthorsCovey PA, Kondo K, Welch L, Frank E, Sianta S, Kumar A, Nuñez R, Lopez-Casado G, van der Knaap E, Rose JKC, McClure BA, Bedinger PA
JournalPlant J
Date Published2010 Nov
KeywordsAmino Acid Sequence, Chromosome Mapping, Genes, Plant, Hybridization, Genetic, Lycopersicon esculentum, Molecular Sequence Data, Plant Proteins, Pollen Tube, Pollination, Quantitative Trait Loci, Reproduction, Ribonucleases, Sequence Alignment, Sequence Homology, Amino Acid

Wild tomato species in Solanum Section Lycopersicon often exhibit two types of reproductive barriers: self-incompatibility (SI) and unilateral incompatibility or incongruity (UI), wherein the success of an inter-specific cross depends on the direction of the cross. UI pollen rejection often follows the 'SI × SC' rule, i.e. pistils of SI species reject the pollen of SC (self-compatible) species but not vice versa, suggesting that the SI and UI pollen rejection mechanisms may overlap. In order to address this question, pollen tube growth was measured after inter-specific crosses using wild tomato species as the female parents and pollen from cultivated tomato (Solanum lycopersicum). Two modes of UI pollen rejection, early and late, were observed, and both differed from SI pollen rejection. The structure and expression of known stylar SI genes were evaluated. We found that S-RNase expression is not required for either the early or late mode of UI pollen rejection. However, two HT family genes, HT-A and HT-B, map to a UI QTL. Surprisingly, we found that a gene previously implicated in SI, HT-B, is mutated in both SI and SC S. habrochaites accessions, and no HT-B protein could be detected. HT-A genes were detected and expressed in all species examined, and may therefore function in both SI and UI. We conclude that there are significant differences between SI and UI in the tomato clade, in that pollen tube growth differs between these two rejection systems, and some stylar SI factors, including S-RNase and HT-B, are not required for UI.

Alternate JournalPlant J.
PubMed ID20804455

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