Physiological and Genetic Bases of the Circadian Clock in Plants and Their Relationship with Herbicides Efficacy

In order to adapt to daily environmental changes, especially in relation to light availability, many organisms, such as plants, developed a vital mechanism that controls time-dependent biological events: the circadian clock. The circadian clock is responsible for predicting the changes that occur in the period of approximately 24 hours, preparing the plants for the following phases of the cycle. Some of these adaptations can influence the response of weeds to the herbicide application. Thus, the objectives of this review are to describe the physiological and genetic mechanisms of the circadian clock in plants, as well as to demonstrate the relationship of this phenomenon with the effectiveness of herbicides for weed control. Relationships are described between the circadian clock and the time of application of herbicides, leaf angle and herbicide interception, as well as photosynthetic activity in response to the circadian clock and herbicide efficiency. Further, it is discussed the role of phytochrome B (phyB) in the sensitivity of plants to glyphosate herbicide. The greater understanding of the circadian clock in plants is essential to achieve greater efficiency of herbicides and hence greater control of weeds and higher crop yields.

The search for circadian clock components in humans: new perspectives for association studies

Individual circadian clocks entrain differently to environmental cycles (zeitgebers, e.g., light and darkness), earlier or later within the day, leading to different chronotypes. In human populations, the distribution of chronotypes forms a bell-shaped curve, with the extreme early and late types _ larks and owls, respectively _ at its ends. Human chronotype, which can be assessed by the timing of an individual's sleep-wake cycle, is partly influenced by genetic factors - known from animal experimentation. Here, we review population genetic studies which have used a questionnaire probing individual daily timing preference for associations with polymorphisms in clock genes. We discuss their inherent limitations and suggest an alternative approach combining a short questionnaire (Munich ChronoType Questionnaire, MCTQ), which assesses chronotype in a quantitative manner, with a genome-wide analysis (GWA). The advantages of these methods in comparison to assessing time-of-day preferences and single nucleotide polymorphism genotyping are discussed. In the future, global studies of chronotype using the MCTQ and GWA may also contribute to understanding the influence of seasons, latitude (e.g., different photoperiods), and climate on allele frequencies and chronotype distribution in different populations.

The expression of melanopsin and clock genes in Xenopus laevis melanophores and their modulation by melatonin

Vertebrates have a central clock and also several peripheral clocks. Light responses might result from the integration of light signals by these clocks. The dermal melanophores of Xenopus laevis have a photoreceptor molecule denominated melanopsin (OPN4x). The mechanisms of the circadian clock involve positive and negative feedback. We hypothesize that these dermal melanophores also present peripheral clock characteristics. Using quantitative PCR, we analyzed the pattern of temporal expression of Opn4x and the clock genes Per1, Per2, Bmal1, and Clock in these cells, subjected to a 14-h light:10-h dark (14L:10D) regime or constant darkness (DD). Also, in view of the physiological role of melatonin in the dermal melanophores of X. laevis, we determined whether melatonin modulates the expression of these clock genes. These genes show a time-dependent expression pattern when these cells are exposed to 14L:10D, which differs from the pattern observed under DD. Cells kept in DD for 5 days exhibited overall increased mRNA expression for Opn4x and Clock, and a lower expression for Per1, Per2, and Bmal1. When the cells were kept in DD for 5 days and treated with melatonin for 1 h, 24 h before extraction, the mRNA levels tended to decrease for Opn4x and Clock, did not change for Bmal1, and increased for Per1 and Per2 at different Zeitgeber times (ZT). Although these data are limited to one-day data collection, and therefore preliminary, we suggest that the dermal melanophores of X. laevis might have some characteristics of a peripheral clock, and that melatonin modulates, to a certain extent, melanopsin and clock gene expression.

Important state papers : declaration of war, Washington, June 18, 4 o'clock, P.M.

Message to the Senate and House of Representatives of the United States / James Madison -- Report : the Committee on Foreign relations, to whom was referred the message of the President of the United States of the 1st of June, 1812 -- An Act, declaring war between the United Kingdom of Great Britain and Ireland and the dependencies thereof, and the United States of America and their territories -- Address of the Senate to the people of the Commonwealth of Massachusetts.

Developing a numerical inverse-theory-based extraction of orientation-dependent relaxation rates from partially- relaxed spectra

Second-rank tensor interactions, such as quadrupolar interactions between the spin- 1 deuterium nuclei and the electric field gradients created by chemical bonds, are affected by rapid random molecular motions that modulate the orientation of the molecule with respect to the external magnetic field. In biological and model membrane systems, where a distribution of dynamically averaged anisotropies (quadrupolar splittings, chemical shift anisotropies, etc.) is present and where, in addition, various parts of the sample may undergo a partial magnetic alignment, the numerical analysis of the resulting Nuclear Magnetic Resonance (NMR) spectra is a mathematically ill-posed problem. However, numerical methods (de-Pakeing, Tikhonov regularization) exist that allow for a simultaneous determination of both the anisotropy and orientational distributions. An additional complication arises when relaxation is taken into account. This work presents a method of obtaining the orientation dependence of the relaxation rates that can be used for the analysis of the molecular motions on a broad range of time scales. An arbitrary set of exponential decay rates is described by a three-term truncated Legendre polynomial expansion in the orientation dependence, as appropriate for a second-rank tensor interaction, and a linear approximation to the individual decay rates is made. Thus a severe numerical instability caused by the presence of noise in the experimental data is avoided. At the same time, enough flexibility in the inversion algorithm is retained to achieve a meaningful mapping from raw experimental data to a set of intermediate, model-free

Important state papers : declaration of war, Washington, June 18, 4 o'clock, P.M

Message to the Senate and House of Representatives of the United States / James Madison -- Report : the Committee on Foreign relations, to whom was referred the message of the President of the United States of the 1st of June, 1812 -- An Act, declaring war between the United Kingdom of Great Britain and Ireland and the dependencies thereof, and the United States of America and their territories -- Address of the Senate to the people of the Commonwealth of Massachusetts.

Receipt from Burrill, McEwen and Co. for Chinese clock

Receipt from Burrill, McEwen and Co. for Chinese clock, Oct. 12, 1876.

Strained Silicon on Silicon by Wafer Bonding and Layer Transfer from Relaxed SiGe Buffer

We report the creation of strained silicon on silicon (SSOS) substrate technology. The method uses a relaxed SiGe buffer as a template for inducing tensile strain in a Si layer, which is then bonded to another Si handle wafer. The original Si wafer and the relaxed SiGe buffer are subsequently removed, thereby transferring a strained-Si layer directly to Si substrate without intermediate SiGe or oxide layers. Complete removal of Ge from the structure was confirmed by cross-sectional transmission electron microscopy as well as secondary ion mass spectrometry. A plan-view transmission electron microscopy study of the strained-Si/Si interface reveals that the lattice-mismatch between the layers is accommodated by an orthogonal array of edge dislocations. This misfit dislocation array, which forms upon bonding, is geometrically necessary and has an average spacing of approximately 40nm, in excellent agreement with established dislocation theory. To our knowledge, this is the first study of a chemically homogeneous, yet lattice-mismatched, interface.

Characterisation of an amphioxus Fringe gene and the evolution of the vertebrate segmentation clock

In mouse and chick embryos, cyclic expression of lunatic fringe has an important role in the regulation of mesoderm segmentation. We have isolated a Fringe gene from the protochordate amphioxus. Amphioxus is the closest living relative of the vertebrates, and has mesoderm that is definitively segmented in a manner that is similar to, and probably homologous with, that of vertebrates. AmphiFringe is placed basal to vertebrate Fringe genes in molecular phylogenetic analyses, indicating that the duplications that formed radical-, manic- and lunatic fringe are specific to the vertebrate lineage. AmphiFringe expression was detected in the anterior neural plate of early neurulae, where it resolved into a series of segmental patches by the mid-neurulae stage. No AmphiFringe transcripts were detected in the mesoderm. Based on these observations, we propose a model depicting a successive recruitment of Fringe in the maintenance then regulation of segmentation during vertebrate evolution.

A low clock frequency FFT core implementation for multiband full-rate ultra-wideband (UWB) receivers

This paper discusses the design, implementation and synthesis of an FFT module that has been specifically optimized for use in the OFDM based Multiband UWB system, although the work is generally applicable to many other OFDM based receiver systems. Previous work has detailed the requirements for the receiver FFT module within the Multiband UWB ODFM based system and this paper draws on those requirements coupled with modern digital architecture principles and low power design criteria to converge on our optimized solution particularly aimed at a low-clock rate implementation. The FFT design obtained in this paper is also applicable for implementation of the transmitter IFFT module therefore only needing one FFT module in the device for half-duplex operation. The results from this paper enable the baseband designers of the 200Mbit/sec variant of Multiband UWB systems (and indeed other OFDM based receivers) using System-on-Chip (SoC), FPGA and ASIC technology to create cost effective and low power consumer electronics product solutions biased toward the very competitive market.

An extreme case of plant-insect co-diversification: figs and fig-pollinating wasps

It is thought that speciation in phytophagous insects is often due to colonization of novel host plants, because radiations of plant and insect lineages are typically asynchronous. Recent phylogenetic comparisons have supported this model of diversification for both insect herbivores and specialized pollinators. An exceptional case where contemporaneous plant insect diversification might be expected is the obligate mutualism between fig trees (Ficus species, Moraceae) and their pollinating wasps (Agaonidae, Hymenoptera). The ubiquity and ecological significance of this mutualism in tropical and subtropical ecosystems has long intrigued biologists, but the systematic challenge posed by >750 interacting species pairs has hindered progress toward understanding its evolutionary history. In particular, taxon sampling and analytical tools have been insufficient for large-scale co-phylogenetic analyses. Here, we sampled nearly 200 interacting pairs of fig and wasp species from across the globe. Two supermatrices were assembled: on average, wasps had sequences from 77% of six genes (5.6kb), figs had sequences from 60% of five genes (5.5 kb), and overall 850 new DNA sequences were generated for this study. We also developed a new analytical tool, Jane 2, for event-based phylogenetic reconciliation analysis of very large data sets. Separate Bayesian phylogenetic analyses for figs and fig wasps under relaxed molecular clock assumptions indicate Cretaceous diversification of crown groups and contemporaneous divergence for nearly half of all fig and pollinator lineages. Event-based co-phylogenetic analyses further support the co-diversification hypothesis. Biogeographic analyses indicate that the presentday distribution of fig and pollinator lineages is consistent with an Eurasian origin and subsequent dispersal, rather than with Gondwanan vicariance. Overall, our findings indicate that the fig-pollinator mutualism represents an extreme case among plant-insect interactions of coordinated dispersal and long-term co-diversification.

Developing social skills in autistic children through ‘Relaxed Performances’

Families living with autism often feel unable to attend social and cultural events largely due to the fear of their child attracting negative or even aggressive reactions from others. The ‘joint attention’ that is part of the theatre experience however may be a powerful factor in the development of social and communication skills for such children. ‘Relaxed performances’ offer an opportunity for them to access and engage with theatre by making special arrangements designed to reduce tensions associated with visits to public places. Aspects of the production such as the use of lighting and sound effects which may trigger adverse reactions are also adjusted. This paper reports on how one local theatre drew on the findings of a national project to mount a ‘relaxed performance’ of their annual pantomime. It discusses the theatre’s preparations and presents evidence of the impact the event had on local children with autism and their families. The success of both the national and this local project marks a new beginning for improved access to the theatre for an audience that has hitherto felt largely excluded.

Modeling the observed proton aurora and ionospheric convection responses to changes in the IMF clock angle: 2. Persistence of ionospheric convection

We apply a numerical model of time-dependent ionospheric convection to two directly driven reconnection pulses during a 15-min interval of southward IMF on 26 November 2000. The model requires an input magnetopause reconnection rate variation, which is here derived from the observed variation in the upstream IMF clock angle, q. The reconnection rate is mapped to an ionospheric merging gap, the MLT extent of which is inferred from the Doppler-shifted Lyman-a emission on newly opened field lines, as observed by the FUV instrument on the IMAGE spacecraft. The model is used to reproduce a variety of features observed during this event: SuperDARN observations of the ionospheric convection pattern and transpolar voltage; FUV observations of the growth of patches of newly opened flux; FUVand in situ observations of the location of the Open-Closed field line Boundary (OCB) and a cusp ion step. We adopt a clock angle dependence of the magnetopause reconnection electric field, mapped to the ionosphere, of the form Enosin4(q/2) and estimate the peak value, Eno, by matching observed and modeled variations of both the latitude, LOCB, of the dayside OCB (as inferred from the equatorward edge of cusp proton emissions seen by FUV) and the transpolar voltage FPC (as derived using the mapped potential technique from SuperDARN HF radar data). This analysis also yields the time constant tOCB with which the open-closed boundary relaxes back toward its equilibrium configuration. For the case studied here, we find tOCB = 9.7 ± 1.3 min, consistent with previous inferences from the observed response of ionospheric flow to southward turnings of the IMF. The analysis confirms quantitatively the concepts of ionospheric flow excitation on which the model is based and explains some otherwise anomalous features of the cusp precipitation morphology.

Modeling the observed proton aurora and ionospheric convection responses to changes in the IMF clock angle: 1. Persistence of cusp proton aurora

We employ a numerical model of cusp ion precipitation and proton aurora emission to fit variations of the peak Doppler-shifted Lyman-a intensity observed on 26 November 2000 by the SI-12 channel of the FUV instrument on the IMAGE satellite. The major features of this event appeared in response to two brief swings of the interplanetary magnetic field (IMF) toward a southward orientation. We reproduce the observed spatial distributions of this emission on newly opened field lines by combining the proton emission model with a model of the response of ionospheric convection. The simulations are based on the observed variations of the solar wind proton temperature and concentration and the interplanetary magnetic field clock angle. They also allow for the efficiency, sampling rate, integration time and spatial resolution of the FUV instrument. The good match (correlation coefficient 0.91, significant at the 98% level) between observed and modeled variations confirms the time constant (about 4 min) for the rise and decay of the proton emissions predicted by the model for southward IMF conditions. The implications for the detection of pulsed magnetopause reconnection using proton aurora are discussed for a range of interplanetary conditions.