Insect ecology and veteran trees

Insect and veteran trees are important parts of ecosystems and are usually included in ecological studies of forest management. The loss of veteran trees in woodlands and open landscapes would lead to the loss of saproxylic organisms—an important part of biodiversity. Hence, the persistence of many specialized insects depends on the presence of veteran trees scattered in woodlands (e.g. ancient wood pastures, game parks or protected areas), cities, towns and villages (e.g. avenues, parks or chateau parks) or open landscapes (e.g. fishpond dams, solitary trees or fruit orchards). Veteran tree conditions could be fairly well described by three components—diameter, age and microhabitats present. The problem is that diameter belongs to the most studied characteristics, while age and microhabitats, which can be quite complicated to measure, are much less studied. This paper illustrates that, due to this unbalanced use of indicators of veteran-tree conditions, we are still missing some important information on saproxylic species ecology—and sometimes only large trees might be studied, rather than real veterans. Although we already know that veteran trees are essential habitat for a range of saproxylic organisms, there are still gaps in our knowledge of the specific conditions that veteran trees provide. It is vital that these are quantified and understood so that this information can be used to conserve veteran trees and their associated species.     

Understanding the Role of Dicer in Astrocyte Development

The Dicer1 allele is used to show that microRNAs (miRNAs) play important roles in astrocyte development and functions. While it is known that astrocytes that lack miRNAs are dysregulated, the in vivo phenotypes of these astrocytes are not well understood. In this study, we use Aldh1l1-EGFP transgene, a marker of astrocytes, to characterize mouse models with conditional Dicer1 ablation (via either human or mouse GFAP-Cre). This transgene revealed novel features of the defective astrocytes from the absence of miRNA. Although astrocyte miRNAs were depleted in both lines, we found histological and molecular differences in the Aldh1l1-EGFP cells between the two Cre lines. Aldh1l1-EGFP cells from hGFAP-Cre mutant lines displayed up-regulation of Aldh1l1-EGFP with increased proliferation and a genomic profile that acquired many features of wildtype primary astrocyte cultures. In the young mGFAP-Cre mutant lines we found that Aldh1l1-EGFP cells were disorganized and hyperproliferative in the developing cerebellum. Using the Aldh1l1-EGFP transgene, our work provides new insights into the roles of miRNAs in astrocyte development and the features of astrocytes in these two mouse models.     

An Age-Wise Comparison of Human Airway Smooth Muscle Proliferative Capacity

We compared the proliferation of neonatal and adult airway smooth muscle cells (ASMC) with no/moderate lung disease, in glucose- (energy production by glycolysis) or glucose-free medium (ATP production from mitochondrial oxidative phosphorylations only), in response to 10% fetal calf serum (FCS) and PDGF-AA. In the presence of glucose, cell counts were significantly greater in neonatal vs. adult ASMC. Similarly, neonatal ASMC DNA synthesis in 10% FCS and PDGF-AA, and [Ca²⁺]i responses in the presence of histamine were significantly enhanced vs. adults. In glucose-free medium, cell proliferation was preserved in neonatal cells, unlike in adult cells, with concomitant increased porin (an indicator of mitochondrial activity) protein expression. Compared to adults, stimulated neonatal human ASMC are in a rapid and robust proliferative phase and have the capacity to respond disproportionately under abnormal environmental conditions, through increased mitochondrial biogenesis and altered calcium homeostasis.     

Subgroups of Paediatric Acute Lymphoblastic Leukaemia Might Differ Significantly in Genetic Predisposition to Asparaginase Hypersensitivity

L-asparaginase (ASP) is a key element in the treatment of paediatric acute lymphoblastic leukaemia (ALL). However, hypersensitivity reactions (HSRs) to ASP are major challenges in paediatric patients. Our aim was to investigate genetic variants that may influence the risk to Escherichia coli-derived ASP hypersensitivity. Sample and clinical data collection was carried out from 576 paediatric ALL patients who were treated according to protocols from the Berlin—Frankfurt—Münster Study Group. A total of 20 single nucleotide polymorphisms (SNPs) in GRIA1 and GALNT10 genes were genotyped. Patients with GRIA1 rs4958351 AA/AG genotype showed significantly reduced risk to ASP hypersensitivity compared to patients with GG genotype in the T-cell ALL subgroup (OR = 0.05 (0.01–0.26); p = 4.70E-04), while no such association was found in pre-B-cell ALL. In the medium risk group two SNPs of GRIA1 (rs2055083 and rs707176) were associated significantly with the occurrence of ASP hypersensitivity (OR = 0.21 (0.09–0.53); p = 8.48E-04 and OR = 3.02 (1.36–6.73); p = 6.76E-03, respectively). Evaluating the genders separately, however, the association of rs707176 with ASP HSRs was confined only to females. Our results suggest that genetic variants of GRIA1 might influence the risk to ASP hypersensitivity, but subgroups of patients can differ significantly in this respect.     

A Dynamic Gene Regulatory Network Model That Recovers the Cyclic Behavior of Arabidopsis thaliana Cell Cycle

Cell cycle control is fundamental in eukaryotic development. Several modeling efforts have been used to integrate the complex network of interacting molecular components involved in cell cycle dynamics. In this paper, we aimed at recovering the regulatory logic upstream of previously known components of cell cycle control, with the aim of understanding the mechanisms underlying the emergence of the cyclic behavior of such components. We focus on Arabidopsis thaliana, but given that many components of cell cycle regulation are conserved among eukaryotes, when experimental data for this system was not available, we considered experimental results from yeast and animal systems. We are proposing a Boolean gene regulatory network (GRN) that converges into only one robust limit cycle attractor that closely resembles the cyclic behavior of the key cell-cycle molecular components and other regulators considered here. We validate the model by comparing our in silico configurations with data from loss- and gain-of-function mutants, where the endocyclic behavior also was recovered. Additionally, we approximate a continuous model and recovered the temporal periodic expression profiles of the cell-cycle molecular components involved, thus suggesting that the single limit cycle attractor recovered with the Boolean model is not an artifact of its discrete and synchronous nature, but rather an emergent consequence of the inherent characteristics of the regulatory logic proposed here. This dynamical model, hence provides a novel theoretical framework to address cell cycle regulation in plants, and it can also be used to propose novel predictions regarding cell cycle regulation in other eukaryotes.     

Phenotypic Buffering in a Monogenean: Canalization and Developmental Stability in Shape and Size of the Haptoral Anchors of Ligophorus cephali (Monogenea: Dactylogyridae)

Phenotypic variation results from the balance between sources of variation and counteracting regulatory mechanisms. Canalization and developmental stability are two such mechanisms, acting at two different levels of regulation. The issue of whether or not they act concurrently as a common developmental buffering capacity has been subject to debate. We used geometric morphometrics to quantify the mechanisms that guarantee phenotypic constancy in the haptoral anchors of Ligophorus cephali. Canalization and developmental stability were appraised by estimating inter- and intra-individual variation, respectively, in size and shape of dorsal and ventral anchors. The latter variation was estimated as fluctuating asymmetry (FA) between anchor pairs. The general-buffering-capacity hypothesis was tested by two different methods based on correlations and Principal Components Analyses of the different components of size and shape variation. Evidence for FA in the dorsal and ventral anchors in both shape and size was found. Our analyses supported the hypothesis of a general developmental buffering capacity. The evidence was more compelling for shape than for size and, particularly, for the ventral anchors than for the dorsal ones. These results are in line with previous studies of dactylogyrids suggesting that ventral anchors secure a firmer, more permanent attachment, whereas dorsal anchors are more mobile. Because fixation to the host is crucial for survival in ectoparasites, we suggest that homeostatic development of the ventral anchors has been promoted to ensure the morphological constancy required for efficient attachment. Geometric morphometrics can be readily applied to other host-monogenean models, affording not only to disentangle the effects of canalization and developmental stability, as shown herein, but to further partition the environmental and genetic components of the former.     

Photosynthetic Light Responses May Explain Vertical Distribution of Hymenophyllaceae Species in a Temperate Rainforest of Southern Chile

Some epiphytic Hymenophyllaceae are restricted to lower parts of the host (<60 cm; 10–100 μmol photons m^-2 s^-1) in a secondary forest of Southern Chile; other species occupy the whole host height (≥10 m; max PPFD >1000 μmol photons m^-2 s^-1). Our aim was to study the photosynthetic light responses of two Hymenophyllaceae species in relation to their contrasting distribution. We determined light tolerance of Hymenoglossum cruentum and Hymenophyllum dentatum by measuring gas exchange, PSI and PSII light energy partitioning, NPQ components, and pigment contents. H. dentatum showed lower maximum photosynthesis rates (A_max) than H. cruentum, but the former species kept its net rates (A_n) near A_max across a wide light range. In contrast, in the latter one, A_n declined at PPFDs >60 μmol photons m^-2 s^-1. H. cruentum, the shadiest plant, showed higher chlorophyll contents than H. dentatum. Differences in energy partitioning at PSI and PSII were consistent with gas exchange results. H. dentatum exhibited a higher light compensation point of the partitioning of absorbed energy between photochemical Y(PSII) and non-photochemical Y(NPQ) processes. Hence, both species allocated energy mainly toward photochemistry instead of heat dissipation at their light saturation points. Above saturation, H. cruentum had higher heat dissipation than H. dentatum. PSI yield (YPSI) remained higher in H. dentatum than H. cruentum in a wider light range. In both species, the main cause of heat dissipation at PSI was a donor side limitation. An early dynamic photo-inhibition of PSII may have caused an over reduction of the Qa⁺ pool decreasing the efficiency of electron donation to PSI. In H. dentatum, a slight increase in heat dissipation due to acceptor side limitation of PSI was observed above 300 μmol photons m^-2s^-1. Differences in photosynthetic responses to light suggest that light tolerance and species plasticity could explain their contrasting vertical distribution.