The members of the phytochrome (phy) family of bilin-containing photoreceptors are major regulators of plant photomorphogenesis through their unique ability to photointerconvert between a biologically inactive red light-absorbing Pr state and an active far-red light-absorbing Pfr state. While the initial steps in Pfr signaling are unclear, an early event for the phyB isoform after photoconversion is its redistribution from the cytoplasm into subnuclear foci known as photobodies (PBs), which dissipate after Pfr reverts back to Pr by far-red irradiation or by temperature-dependent nonphotochemical reversion. Here we present evidence that PHOTOPERIODIC CONTROL OF HYPOCOTYL 1 (PCH1) functions both as an essential structural component of phyB-containing PBs and as a direct regulator of thermal reversion that is sufficient to stabilize phyB as Pfr in vitro. By examining the genetic interaction between a constitutively active phyBY276H-YFP allele (
Cryptochromes are blue light‐absorbing photoreceptors found in plants and animals with many important signalling functions. These include control of plant growth, development, and the entrainment of the circadian clock. Plant cryptochromes have recently been implicated in adaptations to temperature variation, including temperature compensation of the circadian clock. However, the effect of temperature directly on the photochemical properties of the cryptochrome photoreceptor remains unknown. Here we show that the response to light of purified
- Award ID(s):
- 1658640
- NSF-PAR ID:
- 10450855
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Physiologia Plantarum
- Volume:
- 172
- Issue:
- 3
- ISSN:
- 0031-9317
- Page Range / eLocation ID:
- p. 1653-1661
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
YHB-YFP ) and PCH1, we show that the loss of PCH1 prevents YHB from coalescing into PBs without affecting its nuclear localization, whereas overexpression of PCH1 dramatically increases PB levels. Loss of PCH1, presumably by impacting phyB-PB assembly, compromises a number of events elicited inYHB-YFP plants, including their constitutive photomorphogenic phenotype, red light-regulated thermomorphogenesis, and input of phyB into the circadian clock. Conversely, elevated levels of both phyB and PCH1 generate stable, yet far-red light–reversible PBs that persisted for days. Collectively, our data demonstrate that the assembly of PCH1-containing PBs is critical for phyB signaling to multiple outputs and suggest that altering PB dynamics could be exploited to modulate plant responses to light and temperature. -
more » « less
Abstract Many animals use the Earth’s geomagnetic field for orientation and navigation. Yet, the molecular and cellular underpinnings of the magnetic sense remain largely unknown. A biophysical model proposed that magnetoreception can be achieved through quantum effects of magnetically-sensitive radical pairs formed by the photoexcitation of cryptochrome (CRY) proteins. Studies in
Drosophila are the only ones to date to have provided compelling evidence for the ultraviolet (UV)-A/blue light-sensitive type 1 CRY (CRY1) involvement in animal magnetoreception, and surprisingly extended this discovery to the light-insensitive mammalian-like type 2 CRYs (CRY2s) of both monarchs and humans. Here, we show that monarchs respond to a reversal of the inclination of the Earth’s magnetic field in an UV-A/blue light and CRY1, but not CRY2, dependent manner. We further demonstrate that both antennae and eyes, which express CRY1, are magnetosensory organs. Our work argues that only light-sensitive CRYs function in animal light-dependent inclination-based magnetic sensing. -
null (Ed.)Cryptochromes are highly conserved blue light-absorbing flavoproteins which function as photoreceptors during plant development and in the entrainment of the circadian clock in animals. They have been linked to perception of electromagnetic fields in many organisms including plants, flies, and humans. The mechanism of magnetic field perception by cryptochromes is suggested to occur by the so-called radical pair mechanism, whereby the electron spins of radical pairs formed in the course of cryptochrome activation can be manipulated by external magnetic fields. However, the identity of the magnetosensitive step and of the magnetically sensitive radical pairs remains a matter of debate. Here we investigate the effect of a static magnetic field of 500 μT (10× earth's magnetic field) which was applied in the course of a series of iterated 5 min blue light/10 min dark pulses. Under the identical pulsed light conditions, cryptochrome responses were enhanced by a magnetic field even when exposure was provided exclusively in the 10 min dark intervals. However, when the magnetic stimulus was given exclusively during the 5 min light interval, no magnetic sensitivity could be detected. This result eliminates the possibility that magnetic field sensitivity could occur during forward electron transfer to the flavin in the course of the cryptochrome photocycle. By contrast, radical pair formation during cryptochrome flavin reoxidation would occur independently of light, and continue for minutes after the cessation of illumination. Our results therefore provide evidence that a magnetically sensitive reaction is entwined with dark-state processes following the cryptochrome photoreduction step.more » « less
-
more » « less
Summary Circadian clocks allow organisms to predict environmental changes caused by the rotation of the Earth. Although circadian rhythms are widespread among different taxa, the core components of circadian oscillators are not conserved and differ between bacteria, plants, animals and fungi. Stramenopiles are a large group of organisms in which circadian rhythms have been only poorly characterized and no clock components have been identified. We have investigated cell division and molecular rhythms in
Nannochloropsis species. In the four strains tested, cell division occurred principally during the night period under diel conditions; however, these rhythms damped within 2–3 days after transfer to constant light. We developed firefly luciferase reporters for the long‐term monitoring ofin vivo transcriptional rhythms in twoNannochlropsis species,Nannochloropsis oceanica CCMP 1779 andNannochloropsis salina CCMP 537. The reporter lines express anticipatory behavior under light/dark cycles and free‐running bioluminescence rhythms with periods of ~21–31 h that damped within ~3–4 days under constant light. Using different entrainment regimes, we demonstrate that these rhythms are modulated by a circadian‐type oscillator. In addition, the phase of free‐running luminescence rhythms can be modulated pharmacologically using aCK 1 ε/δ inhibitor, suggesting a role of this kinase in theNannochloropsis clock. Together with the molecular and genomic tools available forNannochloropsis species, these reporter lines represent an excellent system for future studies on the molecular mechanisms of stramenopile circadian oscillators. -
more » « less
Abstract Biological functions, including glycemic control and bone metabolism, are highly influenced by the body's internal clock. Circadian rhythms are biological rhythms that run with a period close to 24 hours and receive input from environmental stimuli, such as the light/dark cycle. We investigated the effects of circadian rhythm disruption (CRD), through alteration of the light/dark schedule, on glycemic control and bone quality of mice. Ten‐week‐old male mice (C57/BL6, n = 48) were given a low‐fat diet (LFD) or a high‐fat diet (HFD) and kept on a dayshift or altered schedule (RSS3) for 22 weeks. Mice were divided into four experimental groups (n = 12/group): Dayshift/LFD, Dayshift/HFD, RSS3/LFD, and RSS3/HFD. CRD in growing mice fed a HFD resulted in a diabetic state, with a 36.2% increase in fasting glucose levels compared to the Dayshift/LFD group. Micro‐CT scans of femora revealed a reduction in inner and outer surface expansion for mice on a HFD and altered light schedule. Cancellous bone demonstrated deterioration of bone quality as trabecular number and thickness decreased while trabecular separation increased. While HFD increased cortical bone mineral density, its combination with CRD reduced this phenomenon. The growth of mineral crystals, determined by small angle X‐ray scattering, showed HFD led to smaller crystals. Considering modifications of the organic matrix, regardless of diet, CRD exacerbated the accumulation of fluorescent advanced glycation end‐products (fAGEs) in collagen. Strength testing of tibiae showed that CRD mitigated the higher strength in the HFD group and increased brittleness indicated by lower post‐yield deflection and work‐to‐fracture. Consistent with accumulation of fAGEs, various measures of toughness were lowered with CRD, but combination of CRD with HFD protected against this decrease. Differences between strength and toughness results represent different contributions of structural and material properties of bone to energy dissipation. Collectively, these results demonstrate that combination of CRD with HFD impairs glycemic control and have complex effects on bone quality.
