IAB Research Project Description

Collaborative Research: Diversification of the Self-Incompatibility Locus in the Papaveraceae

Diana Wolf, assistant professor of biology, in the Institute of Arctic Biology Research Greenhouse on the University of Alaska Fairbanks campus. Credit: Courtesy of Diana Wolf/IAB/BW/UAF

Naoki Takebayashi, assistant professor of biology, in the Institute of Arctic Biology Research Greenhouse on the University of Alaska Fairbanks campus. Credit: IAB Research Greenhouse.

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Self-recognition loci, such as the self-incompatibility locus of flowering plants, provide the most stunning examples of extreme genetic variation known. The evolutionary process underlying this variation is selection that continuously favors rare alleles. Selection favoring rarity underlies many important processes in nature. It drives the diversification of the immune system genes in humans and may be responsible for the maintenance of sex in plants and animals. Current empirical knowledge of the evolutionary dynamics of gametophytic self-incomaptibility systems comes from just one system, RNase-based incompatibility found in the potato, rose and snapdragon families. This project will develop the gametophytic self-incompatibility locus of the poppy family as an alternative model. This system has several advantages including ease of mating-type determination and the availability of in-vitro assays of rejection reactions. Non-molecular crossing studies in this system have shown frequent and substantial transmission bias of self-incompatibility alleles, a selective force not accounted for by simple models of rare allele advantage. This study will reconstruct the history of diversification of this unique selfincompatibility locus. Our study will provide the first comparison of self-incompatibility loci in which the selective process is the same (gametophytic), but the molecular basis differs. In addition, while many theoretical predictions concerning the evolution of selfincompatibility loci have been supported by empirical data, one common and unexpected finding has been that these systems exhibit rapid early diversification followed by a slowdown in the rate at which new alleles appear. We will determine whether this pattern occurs also in the poppy system. Next we will determine whether the phylogenetic distance between alleles determines their mating success in a cross, as predicted by the two current hypotheses to explain the slowdown of allelic diversification over time. Reciprocal crossing experiments will differentiate between these alternative hypotheses.

Project Funding

National Science Foundation
$227,019.00
1 Jan 2007 – 31 Dec 2010
IAB Proposal #07-001
UAF Grant #G3901
IAB Project #149


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