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In Arabidopsis thaliana, CONSTANS (CO) plays an essential role in the regulation of photoperiodic flowering under long-day conditions. CO protein is stable only in the afternoon of long days, when it induces the expression of FLOWERING LOCUS T (FT), which promotes flowering. The blue-light photoreceptor FLAVIN-BINDING, KELCH REPEAT, F-BOX1 (FKF1) interacts with CO and stabilizes it by an unknown mechanism. Here, we provide genetic and biochemical evidence that FKF1 inhibits CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1)- dependent CO degradation. Light-activated FKF1 has no apparent effect on COP1 stability but can interact with and negatively regulate COP1. We show that FKF1 can inhibit COP1 homodimerization. Mutation of the coiled-coil domain in COP1, which prevents dimer formation, impairs COP1 function in coordinating flowering time. Based on these results, we propose a model whereby the light- and day length-dependent interaction between FKF1 and COP1 controls CO stability to regulate flowering time. [ABSTRACT FROM AUTHOR]

The plant circadian clock coordinates the responses to multiple and often simultaneous environmental challenges that the sessile plant cannot avoid. These responses must be integrated efficiently into dynamic metabolic and physiological networks essential for growth and reproduction. Many of the output pathways regulated by the circadian clock feed back to modulate clock function, leading to the appreciation of the clock as a central hub in a sophisticated regulatory network. In this Review, we discuss the circadian regulation of growth, flowering time, abiotic and biotic stress responses, and metabolism, as well as why temporal 'gating' of these processes is important to plant fitness. [ABSTRACT FROM AUTHOR]

The circadian clock is known to regulate plant innate immunity but the underlying mechanism of this regulation remains largely unclear. We show here that mutations in the core clock component LUX ARRHYTHMO (LUX) disrupt circadian regulation of stomata under free running and Pseudomonassyringae challenge conditions as well as defense signaling mediated by SA and JA, leading to compromised disease resistance. RNA-seq analysis reveals that both clock- and defense-related genes are regulated by LUX. LUX binds to clock gene promoters that have not been shown before, expanding the clock gene networks that require LUX function. LUX also binds to the promoters of EDS1 and JAZ5, likely acting through these genes to affect SA- and JA-signaling. We further show that JA signaling reciprocally affects clock activity. Thus, our data support crosstalk between the circadian clock and plant innate immunity and imply an important role of LUX in this process. Circadian control of plant defence likely reflects plants' ability to coordinate development and defense. Here, Zhang et al. show that LUX regulates stomatal defense and SA/JA signaling, leading to broad-spectrum disease resistance, and that JA signaling can, in turn, regulate clock activity. [ABSTRACT FROM AUTHOR]

In this article the author discusses the article of Wang and colleagues in the February 3, 2011 issue of "Nature," magazine, which deals on the relation between plant immunity and circadian clock. He is critical to the approach employed by the researchers wherein he argues that the genes that responded to hyaloperonospora (H) arabidopsidis have not identified as immune regulators. However, the author mentions that the research of Wang and colleagues is important in the study of plant pathogens.

Focuses on the scope of Charles Darwin's theory of evolution. Extension of Darwinism to different fields of study; Information on a symposium related to Darwinian evolution held at Dartmouth College in Hanover, New Hampshire in October 1999; Heuristic uses of Darwinian theory.