Safeguarding the rare woodland species Gagea spathacea: Understanding habitat requirements is not sufficient

A large proportion of temperate forest plant diversity is found in the herb layer. However, for many of its species, little is known about their autecology, which makes it difficult to assess potential threats and efficiently safeguard the diversity of understorey herbaceous communities. This also applies to Gagea spathacea (Liliaceae), a globally rare spring geophyte, which mainly occurs in deciduous forests of northern Central Europe. We investigated the causal relationships between population characteristics of G. spathacea and abiotic site conditions across different forest communities in the center of its distributional range. Leaf length (a surrogate of the species' vegetative propagation) was positively related to soil moisture and soil nitrogen. Consequently, mean leaf length was highest in moist forest communities of the alliance Alno-Ulmion. Moreover, mean variability in leaf length was lowest in those forests, indicating a higher and more stable vegetative propagation via bulbils. We found no support for a significant relationship between leaf length and leaf density or between leaf length and flower formation. Population density varied strongly among forest sites, but was not related to soil moisture and hardly influenced by soil nitrogen. Our results suggest that soil water and nutrient supply play a vital role in determining the species' vegetative propagation, whereas the duration of habitat continuity is most likely an important determinant of population size and density. Conservation strategies therefore require a better understanding of the complex interrelationships between abiotic site conditions and the historical context-dependency of habitats.     

Long Recording Sequences: How to Track the Intra-Individual Variability of Acoustic Signals

Recently developed acoustic technologies - like automatic recording units - allow the recording of long sequences in natural environments. These devices are used for biodiversity survey but they could also help researchers to estimate global signal variability at various (individual, population, species) scales. While sexually-selected signals are expected to show a low intra-individual variability at relatively short time scale, this variability has never been estimated so far. Yet, measuring signal variability in controlled conditions should prove useful to understand sexual selection processes and should help design acoustic sampling schedules and to analyse long call recordings. We here use the overall call production of 36 male treefrogs (Hyla arborea) during one night to evaluate within-individual variability in call dominant frequency and to test the efficiency of different sampling methods at capturing such variability. Our results confirm that using low number of calls underestimates call dominant frequency variation of about 35% in the tree frog and suggest that the assessment of this variability is better by using 2 or 3 short and well-distributed records than by using samples made of consecutive calls. Hence, 3 well-distributed 2-minutes records (beginning, middle and end of the calling period) are sufficient to capture on average all the nightly variability, whereas a sample of 10 000 consecutive calls captures only 86% of it. From a biological point of view, the call dominant frequency variability observed in H. arborea (116Hz on average but up to 470 Hz of variability during the course of the night for one male) challenge about its reliability in mate quality assessment. Automatic acoustic recording units will provide long call sequences in the near future and it will be then possible to confirm such results on large samples recorded in more complex field conditions.     

Paraxial mesoderm contributes stromal cells to the developing kidney

The development of most, if not all, tubular organs is dependent on signaling between epithelial and stromal progenitor populations. Most often, these lineages derive from different germ layers that are specified during gastrulation, well in advance of organ condensation. Thus, one of the first stages of organogenesis is the integration of distinct progenitor populations into a single embryonic rudiment. In contrast, the stromal and epithelial lineages controlling renal development are both believed to derive from the intermediate mesoderm and to be specified as the kidney develops. In this study we directly analyzed the lineage of renal epithelia and stroma in the developing chick embryo using two independent fate mapping techniques. Results of these experiments confirm the hypothesis that nephron epithelia derive from the intermediate mesoderm. Most importantly, we discovered that large populations of renal stroma originate in the paraxial mesoderm. Collectively, these studies suggest that the signals that subdivide mesoderm into intermediate and paraxial domains may play a role in specifying nephron epithelia and a renal stromal lineage. In addition, these fate mapping data indicate that renal development, like the development of all other tubular organs, is dependent on the integration of progenitors from different embryonic tissues into a single rudiment.     

Cyclic AMP Affects Oocyte Maturation and Embryo Development in Prepubertal and Adult Cattle

High cAMP levels during in vitro maturation (IVM) have been related to improved blastocyst yields. Here, we employed the cAMP/cGMP modulators, forskolin, IBMX, and cilostamide, during IVM to unravel the role of high cAMP in early embryonic development produced from prepubertal and adult bovine oocytes. Oocytes were collected via transvaginal aspiration and randomly assigned to three experimental groups: TCM24 (24h IVM/control), cAMP30 (2h pre-IVM (forskolin-IBMX), 30h IVM-cilostamide), and DMSO30 (Dimethyl Sulfoxide/vehicle control). After IVM, oocytes were fertilized in vitro and zygotes were cultured in vitro to blastocysts. Meiotic progression, cAMP levels, mRNA abundance of selected genes and DNA methylation were evaluated in oocytes. Blastocysts were used for gene expression or DNA methylation analyses. Blastocysts from the cAMP30 groups were transferred to recipients. The cAMP elevation delayed meiotic progression, but developmental rates were not increased. In immature oocytes, mRNA abundance of PRKACA was higher for cAMP30 protocol and no differences were found for PDE3A, SMAD2, ZAR1, PRDX1 and SLC2A8. EGR1 gene was up-regulated in prepubertal cAMP30 immature oocytes and down-regulated in blastocysts from all in vitro treatments. A similar gene expression profile was observed for DNMT3b, BCL2L1, PRDX1 and SLC2A8 in blastocysts. Satellite DNA methylation profiles were different between prepubertal and adult oocytes and blastocysts derived from the TCM24 and DMSO30 groups. Blastocysts obtained from prepubertal and adult oocytes in the cAMP30 treatment displayed normal methylation profiles and produced offspring. These data indicate that cAMP regulates IVM in prepubertal and adult oocytes in a similar manner, with impact on the establishment of epigenetic marks and acquisition of full developmental competency.     

Differentiation of embryonic mouse GH cells and ACTH cells in vitro

The ability of cells that produce growth hormone (GH) and cells that produce adrenocorticotropic hormone (ACTH) to differentiate in various culture media was analyzed by means of ultrastructural immunocytochemistry on 13-day embryonic mouse pituitaries that were maintained in organ culture for 3-11 days. At the time of culture, relatively undifferentiated nongranulated or poorly granulated cells that were unreactive with anti-growth-hormone serum (anti-GH) and anti-adrenocorticotropic-hormone serum (anti-ACTH) were present in the pituitary. After 10-11 days in culture, immunoreactive GH cells were obtained only in media that were supplemented with cortisol, whereas ACTH cells were obtained in all media tested, including Medium 199 alone. In cortisol-supplemented media, the GH cells showed ultrastructural features typical of those that occur in vivo, and anti-GH immunoreactivity was obtained after as little as 3 days in culture, i.e., at a stage comparable to that which occurs in vivo. The results indicate that mouse GH cells are capable of differentiating in Medium 199 supplemented only with cortisol, without the addition of fetal calf serum or insulin; cortisol therefore appears to be an essential component of the embryonic milieu for the production of GH-secretory granules.     

A new antibiotic with known resistance factors,G418, inhibits plant cells

Growth rates of two lines of tobacco ($\text{Nicotiana}\text{tabacum}$) cell suspension cultures were measured in the presence or absence of G418, a new 2-deoxystreptamine antibiotic related to Gentamycin. Cell growth rates of $\text{N}$. $\text{tabacum}$ cv. Burley were inhibited at drug concentrations as low as 1.65 × 10^?7 M. At 4 × 10^?7 M, the doubling time was increased from 1.5 days (control) to 2.3 days (treatment). The drug was lethal to cells at 4 × 10^?6 M, and inhibition was irreversible. Cells of $\text{N}$. $\text{tabacum}$ cv. Wisconsin 38 also were inhibited by the drug, although at slightly higher concentrations (ca. 2–5 fold).In view of our findings, G418 and its associated resistance factors could be of great value in plant genetic engineering.