From dusk till dawn: camera traps reveal the diel patterns of flower feeding by hawkmoths

1. Diel rhythms of foraging activity by animal flower visitors can reflect niche partitioning and are considered an important component of selection on floral traits. However, it has been notoriously difficult to obtain objective information on the patterns of flower visitation by crepuscular and nocturnal insects. 2. Motion-activated cameras were used for field-based studies of hawkmoth foraging behaviour on six African plant species. 3. The results showed that short-tongued hawkmoth species forage mainly around dusk and then sporadically throughout the night, whereas long-tongued hawkmoth species feed consistently throughout the night, with a peak shortly before midnight. 4. These results provide the first quantitative estimates of diel patterns of interactions between multiple hawkmoth and plant species and, when combined with qualitative reports from other studies, suggest that differences in diel activity between the two main hawkmoth functional groups (short- and long-tongued) are consistent across the Old and New Worlds.     

Circadian rhythmicity in the expression of a novel light-regulated rice gene

We have identified and analyzed cDNAs corresponding to a single-copy gene from rice, designated lir1, whose expression exhibits dramatic diurnal fluctuations. The cDNAs encode a putative protein of 128 amino acids with no homology to known proteins. Lir1 mRNA accumulates in the light, reaching maximum and minimum steady-state levels at the end of the light and dark period, respectively. The oscillations of lir1 mRNA abundance persist after the plants have been transferred to continuous light or darkness. Plants germinated in the dark have very low levels of lir1 mRNA, whereas plants germinated in continuous light express lir1 at an intermediate but constant level. These results indicate that lir1 expression is controlled by light and a circadian clock.     

Seasonal trend in movement directions at dawn and dusk: a study on crow and white herons

Crows (Corvus splendens) and white herons (Ardea alba) inhabit the agricultural landscapes nearby human habitats which represent dynamic ecosystem and show seasonal crop patterns. We studied the movement pattern in these birds at dawn and dusk, during solstices (December and June) and equinoxes (March and September). The movement directions were changed from uniform at dawn to a concentrated distribution at dusk all along the season suggesting that morning movements are more exploratory than evening with seasonal differences. Differential use of directions in December than June could be the effect of temperature, food availability or wind direction and speed. During breeding, less number of directions used suggests that birds might be moving towards the directions having high probability of food availability. It is likely that avian dispersal in space and time is dependent on the food availability however, further studies are required to be carried out.     

Natural entrainment without dawn and dusk: the case of the European ground squirrel (Spermophilus citellus).

Observational data collected in the field and in enclosures show that diurnal, burrow-dwelling European ground squirrels (Spermophilus citellus) never were above ground during twilight at dawn or at dusk. The animals emerged on average 4.02 h (SD = 0.45) after civil twilight at dawn and retreated in their burrows on average 2.87 h (SD = 0.47) before civil twilight at dusk. Daily patterns of light perceived by these burrowing mammals were measured with light-sensitive radio collar transmitters in an enclosure (the Netherlands) and in the field (Hungary). The observational data are corroborated by the telemetry data, which show clear daily patterns of timing of light perception including light perceived from the burrow entrances. The first light was observed by the animals on average 3.54 h (enclosure, SD = 0.45) and 3.60 h (field, SD = 0.31) after civil twilight at dawn, whereas the final observed light was on average 3.04 h (enclosure, SD = 0.64) and 2.02 h (field, SD = 0.72) before civil twilight at dusk. Thus, the animals do not perceive the rapid natural light-dark (LD) transitions that occur at civil twilight. Instead, they generate their own pattern of exposure to light within the natural LD cycle. The classical phase response model for entrainment by light or dark pulses cannot explain how the circadian system of this species remains entrained to the external, natural LD cycle while the major LD transitions are created by its own behavior.     

Long-term influence of simulated territorial intrusions on dawn and dusk singing in the Winter Wren: spring versus autumn

Males of many songbird species have peaks of singing activity at dawn and dusk. Singing during those twilight periods can function in territory proclamation, and males are suggested to adjust song output to the level of intruder pressure. We used song playback during the breeding season to simulate intrusions into territories of male Winter Wrens (Troglodytes troglodytes) shortly after dawn. We then compared male singing behaviour during the dawn and dusk chorus before and 1 day after the simulated intrusion. One day after the playback, male Wrens increased their song output before sunrise, which confirms our results from a previous study on dawn singing in autumn territories. At dusk, on the evening following the playback, males slightly increased song output after sunset, but singing activity at dusk was generally very low. We found no significant changes of song output after sunrise, before sunset, and between 2 days of control without playback. These results are consistent with the hypothesis that dawn and dusk singing is important for territory defence in spring. Unlike in autumn, however, increased singing in spring at dawn and dusk could also serve to defend other resources such as fertile mates or to strengthen the pair bond after a territorial challenge. In comparison with the results on autumnal singing, male Wrens started singing earlier at dawn during the breeding season, and they generally sang more songs at dawn and immediately after playback. The increase in absolute numbers of songs sung in the morning after playback seemed greater in spring than in autumn; however, the proportional increase relative to overall song output was similar in both seasons.     

Regulated expression systems for gene therapy

Gene therapy is a promising and rapidly developing field of modern medicine and is expected to improve or even cure the diseases that are incurable with classical therapies. The logics of the development of gene therapy in the nearest future will require the systems wherein a regulation is possible for expression of therapeutic genes. The review considers the currently available regulated gene therapeutic systems, which can be divided into two main classes. One includes the systems wherein external inducers are used to trigger therapeutic gene expression. Systems of the other class are autoregulated and function without an external inducer. The most important first-class expression systems are based on the regulation by tetracycline, rapamycin derivative-induced dimerization, steroid hormones, regulatory RNAs, and physical factors. The most important systems of the second class are regulated by oxygen or glucose levels.     

Tet-On systems for doxycycline-inducible gene expression

The Tet-On advanced inducible gene expression system in vitro is known for genarating robust expression of the desired gene in target cells. The system offers many advantages over other inducible mammalian gene expression systems, such as high specificity, high inducibility, and high absolute expression levels. In this study, the Tet-On advanced inducible gene expression system was applied to induce the expression of the trophoblast cell-surface antigen 2 (Trop-2) gene in vitro and explore the biological functions of Trop-2. 293/pTet-On-Advanced cell lines were generated, and a recombinant vector containing the Trop-2 gene was constructed and transfected into stable cell lines to improve Trop-2 protein expression. In the presence of doxycycline (DOX), the proliferation assay, transwell assay, and wound healing assay were performed to analyze the efficacy of Trop-2. The results showed that the Tet-On advanced inducible gene expression system was established successfully in the cell line 293, Trop-2 protein level in cells was significantly increased, and Trop-2 could enhance growth, migration, and aggression in the cell line 293. This study suggests that the Tet-On advanced inducible gene expression system can induce the expression of interest genes specifically and artificially in vitro and provides a viable and convenient platform for the study of gene function.     

COP9: a new genetic locus involved in light-regulated development and gene expression in arabidopsis.

We report here the identification and characterization of a new Arabidopsis light-regulatory locus, COP9, mutation that leads to a constitutive photomorphogenic phenotype. Dark-grown cop9 seedlings exhibit many morphological characteristics of light-grown seedlings, including short hypocotyls and open and enlarged cotyledons with cell-type and chloroplast differentiation. Furthermore, the cop9 mutation leads to high-level expression of light-inducible genes in the absence of light, probably by altering the promoter activities of these genes. These properties imply that the mutation in the COP9 locus uncouples the light/dark signals from morphogenesis and light-regulated gene expression. In addition, light-grown cop9 mutants are severely dwarfed and are unable to reach maturation and flowering. This adult-lethal phenotype indicates that the COP9 locus also plays a critical role for normal development of the light-grown plant. Similar to cop1 mutants, but not det1, the cop9 mutants show (1) no effect on the phytochrome control of seed germination and (2) deficiency in the dark-adaptive change of expression of light-regulated genes. Our results suggest that the cop9 and cop1 mutations result in the same range of phenotypes and therefore COP9 and COP1 loci may encode closely related components in the same regulatory pathway.     

Towards universal systems for recombinant gene expression

Recombinant gene expression is among the most important techniques used both in molecular and medical research and in industrial settings. Today, two recombinant expression systems are particularly well represented in the literature reporting on recombinant expression of specific genes. According to searches in the PubMed citation database, during the last 15 years 80% of all recombinant genes reported on in the literature were expressed in either the enterobacterium Escherichia coli or the methylotropic yeast Pichia pastoris. Nevertheless, some eukaryotic proteins are misfolded or inadequately posttranslationally modified in these expression systems. This situation demands identification of other recombinant expression systems that enable the proper expression of the remaining eukaryotic genes. As of now, a single universal system allowing expression of all target genes is still a distant goal. In this light, thorough experimental screening for systems that can yield satisfying quantity and quality of target protein is required. In recent years, a number of new expression systems have been described and used for protein production. Two systems, namely Drosophila melanogaster S2 insect cells and human embryonic kidney 293 (HEK293) cells stably expressing the EBNA-1 gene, show exceptional promise. The time has come to identify a few well-performing systems that will allow us to express, purify, and characterize entire eukaryotic genomes.     

Adaptable doxycycline-regulated gene expression systems for Drosophila

We have engineered two new versions of the doxycycline (dox) inducible system for use in Drosophila. In the first system, we have used the ubiquitously expressed Drosophila actin5C promoter to express the Tet-Off transactivator (tTA) in all tissue. Induction of a luciferase target transgene begins 6 h after placing the flies on dox-free food. Feeding drug-free food to mothers results in universal target gene expression in their embryos. Larvae raised on regular food also show robust expression of a target reporter gene. In the second version, we have used the Gal4-UAS system to spatially limit expression of the transactivator. Dox withdrawal results in temporally- and spatially-restricted, inducible expression of luciferase in the adult head and embryo. Both the actin5C and Gal4-UAS versions produce more than 100-fold induction of luciferase in the adult, with virtually no leaky expression in the presence of drug. Reporter gene expression is also undetectable in larvae or embryos from mothers fed dox-containing food. Such tight control may be due to the incorporation of Drosophila insulator elements (SCS and SCS′) into the transgenic vectors. These systems offer a practical, effective alternative to currently available expression systems in the Drosophila research community.