Citation: Nora Scarcelli, James M Cheverud, Barbara A Schaal, Paula X Kover,
(2007)
Antagonistic pleiotropic effects reduce the potential adaptive value of the FRIGIDA locus. Proceedings of the National Academy of Sciences of the United States of America 104(43): Full text doi:10.1073/pnas.0708209104
A sample of F5 plants of Arabidopsis thaliana produced by outbreeding 19 accessions from a worldwide collection. Genetic variation in flowering time is obvious when all plants are simultaneously grown.
Understanding the molecular basis of adaptive evolution is a major goal of evolutionary biology. While a number of candidate genes have been identified lately, thorough analysis of their phenotypic effects have been lacking. Although the occurrence of epistasis and pleiotropy is widely accepted at the molecular level, its effect on the adaptive value of fitness related genes has rarely been investigated in plants. Here we investigate the importance of pleiotropy and epistasis in determining the adaptive value of a candidate gene using the gene FRIGIDA (FRI), which is thought to be the major gene controlling flowering time variation in Arabidopsis thaliana. The effect of FRI on flowering time was analyzed in an outbred population created by randomly mating 19 natural accessions of A. thaliana. This unique population allows the estimation of FRI effects independent of any linkage association with other loci due to demographic processes or to co-adapted genes. It also allows for the estimation of pleiotropic effects of FRI on fitness and inflorescence architecture. We found that although early flowering plants produce more fruits under spring conditions as expected, and non-functional alleles of FRI were associated with early flowering, variation at FRI was not associated with fitness. We show that non-functional FRI alleles have negative pleiotropic effects on fitness by reducing the numbers of nodes and branches on the inflorescence. We propose that these antagonistic pleiotropic effects reduce the adaptive value of FRI, and helps explain the maintenance of alternative life-history strategies across natural populations of A. thaliana.
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