The bypass of ZipA by overexpression of FtsN requires a previously unknown conserved FtsN motif essential for FtsA–FtsN interaction supporting a model in which FtsA monomers recruit late cell division proteins to the Z ring

Assembly of the divisome in Escherichia coli occurs in two temporally distinct steps. First, FtsZ filaments attached to the membrane through interaction with FtsA and ZipA coalesce into a Z ring at midcell. Then, additional proteins are recruited to the Z ring in a hierarchical manner to form a complete divisome, activated by the arrival of FtsN. Recently, we proposed that the interaction of FtsA with itself competes with its ability to recruit downstream division proteins (both require the IC domain of FtsA) and ZipA's essential function is to promote the formation of FtsA monomers. Here, we tested whether overexpression of a downstream division protein could make ZipA dispensable, presumably by shifting the FtsA equilibrium to monomers. Only overexpression of FtsN bypassed ZipA and a conserved motif in the cytoplasmic domain of FtsN was required for both the bypass and interaction with FtsA. Also, this cytoplasmic motif had to be linked to the periplasmic E domain of FtsN to bypass ZipA, indicating that linkage of FtsA to periplasmic components of the divisome through FtsN was essential under these conditions. These results are used to further elaborate our model for the role of FtsA in recruiting downstream division proteins.     

Correlated miR-mRNA Expression Signatures of Mouse Hematopoietic Stem and Progenitor Cell Subsets Predict “Stemness” and “Myeloid” Interaction Networks

Several individual miRNAs (miRs) have been implicated as potent regulators of important processes during normal and malignant hematopoiesis. In addition, many miRs have been shown to fine-tune intricate molecular networks, in concert with other regulatory elements. In order to study hematopoietic networks as a whole, we first created a map of global miR expression during early murine hematopoiesis. Next, we determined the copy number per cell for each miR in each of the examined stem and progenitor cell types. As data is emerging indicating that miRs function robustly mainly when they are expressed above a certain threshold (∼100 copies per cell), our database provides a resource for determining which miRs are expressed at a potentially functional level in each cell type. Finally, we combine our miR expression map with matched mRNA expression data and external prediction algorithms, using a Bayesian modeling approach to create a global landscape of predicted miR-mRNA interactions within each of these hematopoietic stem and progenitor cell subsets. This approach implicates several interaction networks comprising a “stemness” signature in the most primitive hematopoietic stem cell (HSC) populations, as well as “myeloid” patterns associated with two branches of myeloid development.     

Which bovine endometrial cells are the source of and target for lysophosphatidic acid?

The objective of the study was to examine which cultured endometrial cells are the source and which are the target for lysophosphatidic acid (LPA) in the bovine uterus. LPA concentration as well as mRNA and protein expressions of the enzymes responsible for LPA synthesis (phospholipase A2: PLA₂, autotaxin: AX) were greater in epithelial than in stromal cells (P < 0.05). In turn, mRNA and protein expression of LPA receptor (LPAR1) was lower in epithelial than in stromal cells (P < 0.05). We suggest that LPA in bovine endometrium is produced mainly by epithelial cells and affects mostly stromal cells acting via LPAR1.     

Directed Evolution of the Epoxide Hydrolase from Aspergillus niger

An efficient and genetically stable expression system for the directed evolution of epoxide hydrolase from Aspergillus niger (ANEH) has been constructed. Error prone polymerase chain reaction (PCR) with defined mutation rates was used to create biodiversity in two libraries of mutants. Screening for activity allowed the isolation of clones with improved properties. One of these clones shows an expression level 3.4 higher than the original wild type clone in E.?coli SG13009 and a 3.3 fold increased catalytic efficiency on 4-(p-nitrophenoxy)-1,2-epoxybutane. In addition, a screening assay for determining the enantioselectivity in the kinetic resolution of styrene oxide has been established using mass spectrometry.     

Length-weight relationships of 4 coral-reef fish species encountered in Gilbert Islands coastal artisanal fisheries

Length-weight relationships of 4 coral-reef fish species regularly encountered in artisanal coastal fisheries across 5 atolls of the Gilbert Islands, Kiribati, were obtained. The data were collected through creel surveys undertaken randomly over a period of 20–100 days each year between 2013 and 2020. The main fishing methods used were gillnetting (minimum legal mesh size of 63.5 mm), handlining and spearfishing. Fish were weighed using a digital scale calibrated to ±1–5 g and measured on a flat one-meter ruler delineated in 5 mm increments. Parameters a and b extracted from the general form of the equation describing the relationship between length and weight (W = aL^b), associated 95% Confidence Intervals (CI) and correlation coefficients (r²) are presented here.     

The impact of slow stomatal kinetics on photosynthesis and water use efficiency under fluctuating light

Dynamic light conditions require continuous adjustments of stomatal aperture. The kinetics of stomatal conductance (g_s) is hypothesized to be key to plant productivity and water use efficiency (WUE). Using step-changes in light intensity, we studied the diversity of light-induced g_s kinetics in relation to stomatal anatomy in five banana genotypes (Musa spp.) and modeled the impact of both diffusional and biochemical limitations on photosynthesis (A). The dominant A limiting factor was the diffusional limitation associated with g_s kinetics. All genotypes exhibited a strong limitation of A by g_s, indicating a priority for water saving. Moreover, significant genotypic differences in g_s kinetics and g_s limitations of A were observed. For two contrasting genotypes, the impact of differential g_s kinetics was further investigated under realistic diurnally fluctuating light conditions and at the whole-plant level. Genotype-specific stomatal kinetics observed at the leaf level was corroborated at whole-plant level by transpiration dynamics, validating that genotype-specific responses are still maintained despite differences in g_s control at different locations in the leaf and across leaves. However, under diurnally fluctuating light conditions the impact of g_s speediness on A and intrinsic (_iWUE) depended on time of day. During the afternoon there was a setback in kinetics: absolute g_s and g_s responses to light were damped, strongly limiting A and impacting diurnal _iWUE. We conclude the impact of differential g_s kinetics depended on target light intensity, magnitude of change, g_s prior to the change in light intensity, and particularly time of day.     

Inhibition of leukotriene receptors boosts neural progenitor proliferation

Neural stem and progenitor cells serve as a reservoir for new neurons in the adult brain throughout lifetime. One of the critical steps determining the net production of new neurons is neural progenitor proliferation, which needs to be tightly controlled. Since inflammation has detrimental effects on neurogenesis and the 5-lipoxygenase/leukotriene pathway is involved in inflammatory processes, we investigated the effects of leukotrienes and montelukast, a small molecule inhibitor of the leukotriene receptors CysLT(1)R and GPR17, on neural stem and progenitor cell proliferation. We demonstrate expression of the leukotriene receptor GPR17 by neural progenitors and by neural stem cells. Stimulation with excess amounts of leukotrienes did not affect progenitor proliferation, whereas blockade of GPR17 with montelukast strongly elevated neural stem and progenitor proliferation, while maintaining their differentiation fate and potential. This effect was associated with increased ERK1/2 phosphorylation suggesting an involvement of the EGF signaling cascade. Based on our results, montelukast and the inhibition of the 5-LOX pathway might be potent candidates for future therapies employing neurogenesis to promote structural and functional improvement in neurodegeneration, neuropsychiatric disease and ageing.     

A new heterolobosean amoeba Solumitrus palustris n. g., n. sp. isolated from freshwater marsh soil

During the course of research on the bacterial feeding behavior and resistance of amoebae to virulent pathogens, we isolated a new strain of amoeba from organic rich soil at the margin of freshwater swamp in the northeastern United States. Light microscopic morphology is characteristically heterolobosean, resembling vahlkampfiids, including a broadened, limax shape, and eruptive locomotion, but occasionally becoming more contracted and less elongated with lateral or anterior bulges and somewhat branching sparse, uroidal filaments. Electron microscopic evidence, including mitochondria with flattened cristae surrounded by rough endoplasmic reticulum, further indicates a heterolobosean affinity. The solitary nucleus contains a centrally located nucleolus. Cysts are rounded with occasionally an eccentrically located nucleus. The cyst walls are relatively thin, becoming crenated, and loosely enclosing the cyst when mature. Molecular genetic evidence places this isolate among the Heterolobosea, branching most closely in a clade including Allovahlkampfia spelaea and previously isolated, un-named strains of soil amoebae. Based on differentiated features, including morphology of the uroid, cyst wall structure, and molecular genetic evidence that distinguish it from A. spelaea, a new genus and species, Solumitrus palustris, is proposed for this new heterolobosean.