Light-sensitive plasticity genes in Arabidopsis thaliana: Mutant analysis and ecological genetics

To explore how altered plasticity genes affect whole-plant phenotypes and p lant fecundity, we conducted an experiment with isogenic lines of Arabidops is thaliana, representing a wild type and seven photomorphogenic mutants. W e exposed all genotypes to a 3 x 3 factorial array of light intensity and w ater availability. We documented altered plasticity to light intensity not only for mutants insensitive to blue wavelengths, but also for mutants inse nsitive to red and far-red wavelengths. Our results are consistent with mod els of co-action between these two distinct photoreceptory systems. Photomo rphogenic mutants showed altered plasticity to light intensity not only for seedling and rosette morphology, but also for the duration of the vegetati ve and reproductive phases. Fruit production and two other performance trai ts showed no significant variation for plasticity to light intensity, but t he means of all three performance traits differed significantly among genot ypes. Notably, mean fruit production was much lower in the wild type than i n the blue-insensitive and far-red insensitive mutants. The high fruit prod uction of these mutants declined with decreasing water availability. In con trast, the low fruit production of the wild type was quite stable with decl ining water. However, we found only marginally significant variation among genotypes for the water-mediated plasticity of fruit production. Our compar isons of photomorphogenic mutants and wild-type plants suggest that there m ay be significant costs associated with the photoreceptory systems. However , the enhanced fitness of mutant genotypes may not be realizable in natural conditions, where very low water availability or curtailed growing seasons may be common.