Molecular Ecology and Evolution
Miller, Jill S. , Savage, Anna E. .
Gametophytic self-incompatibility in Lycium (Solanaceae): Allelic diversity and patterns of evolution at the S-RNase gene.
GENETICALLY controlled self-incompatibility systems are widespread among angiosperms and have evolved repeatedly, presumably as a mechanism to avoid self-fertilization and enforce outcrossing. Solanaceae is a model system for the study of gametophytic self-incompatibility, and two genes are known to control the incompatibility reaction, one expressed in the pistil and another in the pollen. Previous studies of Lycium parishii (Solanaceae) from Organ Pipe National Monument, Arizona, demonstrated that fruit production, seed set, and pollen tube number in a natural population of this species was significantly higher following outcross (compared to self) pollination. Here I characterize allelic diversity at the S-RNase gene controlling the pistil side of the self-incompatibility reaction for members of this population. Consistent with expectations for self-incompatibility, individuals were heterozygous, and within population allelic diversity was high. In addition, patterns of molecular evolution are consistent with the presence of self-incompatibility. Specifically, site-specific models investigating patterns of selection indicate that positive (diversifying) selection occurs in those regions of the S-RNase gene hypothesized as important in the recognition response, whereas positive selection was not detected for any position within regions previously characterized as conserved. A ten-species genealogy including S-RNases from a pair of congeners from each of five genera in Solanaceae reveals extensive transgeneric evolution of L. parishii S-RNases. Surprisingly, two S-RNases from L. parishii are identical to two previously reported alleles for L. andersonii, suggesting gene flow between these species.
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Miller lab website
1 - Amherst College, Department of Biology, Mcguire Life Sciences Building, Amherst, Massachusetts, 01002, USA
2 - Cornell University, Ecology and Evolutionary Biology, Ithaca, New York, 14853, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 31st, 2006
Time: 2:45 PM