Circadian rhythms confer a higher level of fitness to XXXX plants.

@entity15585 @entity958 @entity59376
Circadian rhythms have been demonstrated in organisms across the taxonomic spectrum. In view of their widespread occurrence, the adaptive significance of these rhythms is of interest. We have previously shown that constitutive expression of the @entity15585 ( @entity15585 ) gene in @entity958 plants ( @entity15585 -ox) results in loss of circadian rhythmicity. Here, we demonstrate that these @entity15585 -ox plants retain the ability to respond to diurnal changes in light. Thus, transcript levels of several circadian-regulated genes, as well as @entity15585 itself and the closely related LHY, oscillate robustly if @entity15585 -ox plants are grown under diurnal conditions. However, in contrast with wild-type plants in which transcript levels change in anticipation of the dark/light transitions, the @entity15585 -ox plants have lost the ability to anticipate this daily change in their environment. We have used @entity15585 -ox lines to examine the effects of loss of circadian regulation on the fitness of an organism. @entity15585 -ox plants flowered later, especially under long-day conditions, and were less viable under very short-day conditions than their wild-type counterparts. In addition, we demonstrate that two other circadian rhythm mutants, @entity59376 , have low-viability phenotypes. Our findings demonstrate the adaptive advantage of circadian rhythms in @entity958 .
