Different Positively Selected Sites at the Gametophytic Self-Incompatibility Pistil S-RNase Gene in the Solanaceae and Rosaceae (Prunus, Pyrus, and Malus)
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In this work we perform a comparative study on the location of positively selected sites (those likely responsible for defining specificity differences) at the S-RNase gene, the pistil component of the gametophytic self-incompatibility system. For Plantaginaceae and Rosaceae (Prunus and Pyrus/Malus) this is the first study of this kind. A clear sign of positive selection was observed for 13, 17, and 27 amino acid sites in Solanaceae, Prunus, and Pyrus/Malus, respectively, using two different methodologies. In Plantaginaceae no clear positively selected sites were identified. Possible reasons for this result are discussed. Indirect experimental evidence suggests that the identified positively selected amino acid sites play a role in specificity determination. The percentage of positively selected sites is similar in Solanaceae and Rosaceae but the location of those sites is different.
KeywordsGametophytic self-incompatibility S-RNase Positive selection
We thank Professor Amy Iezzoni, the Editor in Chief, Professor Martin Kreitman, the Associate Editor Professor, Brian Morton, and the anonymous reviewers for helpful comments. This work was partially funded by Fundação para a Ciência e Tecnologia (research projects POCTI/AGG/44800/2002 and POCI/BIA-BDE/59887/2004 funded by POCI 2010, cofunded by FEDER funds).
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