CALLAHAN, HS; DHANOOLAL, N; Barnard College, Columbia University; Barnard College: Quantifying and interpreting maintenance costs of phenotypic plasticity using recombinant inbred lines of Arabidopsis thaliana

Like many plant species, Arabidopsis thaliana shows phenotypic plasticity for many traits and in response to diverse stimuli. Yet it has not evolved to a point where it survives and reproduces in all environments. Such observations motivate theory about fitness costs associated with plasticity, such as �maintenance costs� for sustaining sensory and response pathways and �genetic costs� associated with pleiotropic or epistatic effects of the genes involving in detection and transduction of signals. Using the segregating variation found in the Somerville Columbia x Kashmir Recombinant Inbred Lines, we quantified plasticity costs of plasticity to vernalization, an extended exposure to chilling temperatures. Replicate plants of each RIL were grown in both brief and long vernalization treatments. Then, for each RIL we quantified (1) environment-specific fitness, (2) environment-specific flowering time, and (3) plasticity induced by the contrasting treatments. A multiple regression model then examined dependence of a RIL�s mean fitness on its mean flowering time and its plasticity. We verified that some RILs are Kashmir-like and plastic, showing accelerated flowering after vernalization; others are Columbia-like and lack plasticity. When rosettes were chilled only briefly, we detected significant plasticity costs. When rosettes were exposed to lengthy vernalization, maintenance costs were not detected. This is a novel approach to the study of plasticity costs, because costs are interpretable. This is because the roles of the FRIGIDA, FLOWERING LOCUS C, and other vernalization-sensitive genes are very well-characterized in the Arabidopsis model system, and because there is allelic variation for FRIGIDA in this particular recombinant inbred population .