Skeletal resorption in bryozoans: occurrence,function and recognition

Skeletal resorption – the physiological removal of mineralised parts by an organism – is an important morphogenetic process in bryozoans. Reports of its occurrence and function across the phylum are patchy, however, and have not previously been synthesised. Here we show that resorption occurs routinely across a wide range of bryozoan clades, colony sizes, growth forms, ontogenetic stages, body wall types, skeletal ultrastructures and mineralogies. Beginning in the early Paleozoic, different modes and functions of resorption have evolved convergently among disparate groups, highlighting its utility as a morphogenetic mode in this phylum. Its functions include branch renovation, formation of branch articulations, excavation of reproductive chambers, part‐shedding, and creation of access portals for budding beyond previously formed skeletal walls. Bryozoan skeletons can be altered by resorption at microscopic, zooidal and colony‐wide scales, typically with a fine degree of control and coordination. We classified resorption patterns in bryozoans according to the morphology and function of the resorption zone (window formation, abscission or excavation), timing within the life of the skeletal element resorbed (primary or secondary), and scale of operation (zooidal or multizooidal). Skeletal resorption is probably greatly underestimated in terms of its utility and role in bryozoan life history, and its prevalence across taxa, especially in fossil forms. It is reported proportionally more frequently in stenolaemates than in gymnolaemates. Some modes of resorption potentially alter or remove the spatial–temporal record of calcification preserved within a skeleton. Consequently, knowledge that resorption has occurred can be relevant for some common applications of skeletal analysis, such as palaeoenvironmental interpretation, or growth and ageing studies. To aid recognition we provide scanning electron microscopy, backscattered electron scanning electron microscopy and transmission electron microscopy examples of skeletal ultrastuctures modified by resorption.     

A concise synthesis of peramine,a metabolite of endophytic fungi

ABSTRACT

The total synthesis of peramine, a natural product isolated from an endophytic fungi, has been achieved in four steps and 34% overall yield from known compounds. The key step was the one-pot construction of the pyrrolopyrazinone ring from pyrrole amide and propargyl bromide. The preparation of peramine-d₄ as an internal standard for quantitative analysis by MS is also described.     

Rate-adjusted cross-linking reaction by photoresponsive α-bromoaldehyde (PBA)-conjugated ODN

We developed a photoresponsive α-bromoaldehyde-conjugated oligonucleotide (PBA-ODN). The PBA-ODN selectively reacted and formed covalent bonds with target oligonucleotides having adenine or cytosine at the frontal position of the aldehyde derivative. Kinetic studies revealed that PBA-ODN has increased kinetic rates for the formation of cross-linked duplexes compared with the corresponding α-chloroaldehyde-conjugated oligonucleotide (PCA-ODN).     

Limited stomatal regulation of the largest-size class of Dryobalanops aromatica in a Bornean tropical rainforest in response to artificial soil moisture reduction

Journal of Plant Research - The physiological response of trees to drought is crucial for understanding the risk of mortality and its feedbacks to climate under the increase in droughts due to...     

Crystal structure of glucansucrase from the dental caries pathogen Streptococcus mutans

Glucansucrase (GSase) from Streptococcus mutans is an essential agent in dental caries pathogenesis. Here, we report the crystal structure of S. mutans glycosyltransferase (GTF-SI), which synthesizes soluble and insoluble glucans and is a glycoside hydrolase (GH) family 70 GSase in the free enzyme form and in complex with acarbose and maltose. Resolution of the GTF-SI structure confirmed that the domain order of GTF-SI is circularly permuted as compared to that of GH family 13 α-amylases. As a result, domains A, B and IV of GTF-SI are each composed of two separate polypeptide chains. Structural comparison of GTF-SI and amylosucrase, which is closely related to GH family 13 amylases, indicated that the two enzymes share a similar transglycosylation mechanism via a glycosyl-enzyme intermediate in subsite − 1. On the other hand, novel structural features were revealed in subsites + 1 and + 2 of GTF-SI. Trp517 provided the platform for glycosyl acceptor binding, while Tyr430, Asn481 and Ser589, which are conserved in family 70 enzymes but not in family 13 enzymes, comprised subsite + 1. Based on the structure of GTF-SI and amino acid comparison of GTF-SI, GTF-I and GTF-S, Asp593 in GTF-SI appeared to be the most critical point for acceptor sugar orientation, influencing the transglycosylation specificity of GSases, that is, whether they produced insoluble glucan with α(1-3) glycosidic linkages or soluble glucan with α(1-6) linkages. The structural information derived from the current study should be extremely useful in the design of novel inhibitors that prevent the biofilm formation by GTF-SI.     

Contractile system of muscle as an auto-oscillator

It is widely known that the contractile system of muscle takes on either the state of contraction (force-generating) or the state of relaxation (non-force-generating), which is known as the "all-or-nothing" principle. However, it is important to note that under intermediate activation conditions there exists a third state, which demonstrates auto-oscillatory properties and is termed SPOC (SPontaneous Oscillatory Contraction) state. We present a phase diagram, in which the states of the contractile system of muscle are divided into three regions consisting of contraction, relaxation and SPOC states. In the present review, experimental data related to the characteristics of SPOC are summarized and the mechanism of SPOC is described. We propose that the bio-motile system itself is an auto-oscillator, even in a membrane-less supra-molecular structure composed of an assembly of molecular motors and cytoskeletons (actin filaments and microtubules). Finally, the physiological significance of SPOC is discussed.     

Functional analyses of the activation loop of phototropin2 in Arabidopsis

Phototropins (phot1 and phot2) are autophosphorylating blue-light receptor kinases that mediate blue-light responses such as phototropism, chloroplast accumulation, and stomatal opening in Arabidopsis (Arabidopsis thaliana). Only phot2 induces the chloroplast avoidance response under strong blue light. The serine (Ser) residues of the kinase activation loop in phot1 are autophosphorylated by blue light, and autophosphorylation is essential for the phot1-mediated responses. However, the role of autophosphorylation in phot2 remains to be determined. In this study, we substituted the conserved residues of Ser-761 and Ser-763 with alanine (S761A S763A) in the phot2 activation loop and analyzed their function by investigating the phot2-mediated responses after the transformation of phot1 phot2 double mutant with this mutant phot2 gene. Transgenic plants expressing the mutant phot2 protein exhibited impaired responses in chloroplast movement, stomatal opening, phototropic bending, leaf flattening, and plant growth; and those expressing phot2 with S761D S763D mutations showed the normal responses. Substitution of both Ser-761 and Ser-763 with alanine in phot2 did not significantly affect the kinase activity in planta. From these results, we conclude that phosphorylation of Ser-761 and Ser-763 in the activation loop may be a common primary step for phot2-mediated responses.     

Domain organization and movements in heavy metal ion pumps: papain digestion of CopA, a Cu+-transporting ATPase

To study domain organization and movements in the reaction cycle of heavy metal ion pumps, CopA, a bacterial Cu+-ATPase from Thermotoga maritima was cloned, overexpressed, and purified, and then subjected to limited proteolysis using papain. Stable analogs of intermediate states were generated using AMPPCP as a nonhydrolyzable ATP analog and AlFx as a phosphate analog, following conditions established for Ca2+-ATPase (SERCA1). Characteristic digestion patterns obtained for different analog intermediates show that CopA undergoes domain rearrangements very similar to those of SERCA1. Digestion sites were identified on the loops connecting the A-domain and the transmembrane helices M2 and M3 as well as on that connecting the N-terminal metal binding domain (NMBD) and the first transmembrane helix, Ma. These digestion sites were protected in the E1P.ADP and E2P analogs, whereas the M2-A-domain loop was cleaved specifically in the absence of ions to be transported, just as in SERCA1. ATPase activity was lost when the link between the NMBD and the transmembrane domain was cleaved, indicating that the NMBD plays a critical role in ATP hydrolysis in T. maritima CopA. The change in susceptibility of the loop between the NMBD and Ma helix provides evidence that the NMBD is associated to the A-domain and recruited into domain rearrangements and that the Ma helix is the counterpart of the M1 helix in SERCA1 and Mb and Mc are uniquely inserted before M2.     

Development and Validation of Arc Nanobodies: New Tools for Probing Arc Dynamics and Function

Neurochemical Research - Activity-regulated cytoskeleton-associated (Arc) protein plays key roles in long-term synaptic plasticity, memory, and cognitive flexibility. However, an integral...     

Folic acid-mediated mitochondrial activation for protection against oxidative stress in human dental pulp stem cells derived from deciduous teeth

Enzymatic antioxidant systems, mainly involving mitochondria, are critical for minimizing the harmful effects of reactive oxygen species, and these systems are enhanced by interactions with nonenzymatic antioxidant nutrients. Because fetal growth requires extensive mitochondrial respiration, pregnant women and fetuses are at high risk of exposure to excessive reactive oxygen species. The enhancement of the antioxidant system, e.g., by nutritional management, is therefore critical for both the mother and fetus. Folic acid supplementation prevents homocysteine accumulation and epigenetic dysregulation associated with one-carbon metabolism. However, few studies have examined the antioxidant effects of folic acid for healthy pregnancy outcomes. The purpose of this study was to elucidate the association between the antioxidant effect of folic acid and mitochondria in undifferentiated cells during fetal growth. Neural crest-derived dental pulp stem cells of human exfoliated deciduous teeth were used as a model of undifferentiated cells in the fetus. Pyocyanin induced excessive reactive oxygen species, resulting in a decrease in cell growth and migration accompanied by mitochondrial fragmentation and inactivation in dental pulp stem cells. This damage was significantly improved by folic acid, along with decreased mitochondrial reactive oxygen species, PGC-1α upregulation, DRP1 downregulation, mitochondrial elongation, and increased ATP production. Folic acid may protect undifferentiated cells from oxidative damage by targeting mitochondrial activation. These results provide evidence for a new benefit of folic acid in pregnant women and fetuses.