A flavone glycoside from the stem of Ixora arborea

A new flavone glycoside isolated from the stem of Ixora arborea has been characterized as chrysin 5-O-β-D-xylopyranoside on the basis of spectral data, colour reactions and degradation studies.     

Possible influences of a macroalgal bloom in eelgrass beds on fish assemblages in the lower Knysna Estuary,South Africa

The occurrence of a macroalgal bloom at eelgrass (Zostera capensis) sampling sites in the summer of 2014/2015 provided an opportunity to use underwater video cameras to monitor the possible effects of environmental change on fish diversity and abundance in the lower reaches of the Knysna Estuary. A General Linear Model (GLM) showed that there was a significant difference in the abundance of fish before and after an invasion of the sampling sites by the macroalga Ulva lactuca. The eelgrass bed fish abundance was more affected by the macroalgal bloom than the bare substratum fish abundance, with the Ulva impacting negatively on the relative abundance of Mugilidae in the former habitat. The hypothesis that macroalgal invasions have a negative effect on fish diversity and abundance is therefore supported by this preliminary study.     

The Characteristics of Heterozygous Protein Truncating Variants in the Human Genome

Sequencing projects have identified large numbers of rare stop-gain and frameshift variants in the human genome. As most of these are observed in the heterozygous state, they test a gene’s tolerance to haploinsufficiency and dominant loss of function. We analyzed the distribution of truncating variants across 16,260 autosomal protein coding genes in 11,546 individuals. We observed 39,893 truncating variants affecting 12,062 genes, which significantly differed from an expectation of 12,916 genes under a model of neutral de novo mutation (p<10⁻⁴). Extrapolating this to increasing numbers of sequenced individuals, we estimate that 10.8% of human genes do not tolerate heterozygous truncating variants. An additional 10 to 15% of truncated genes may be rescued by incomplete penetrance or compensatory mutations, or because the truncating variants are of limited functional impact. The study of protein truncating variants delineates the essential genome and, more generally, identifies rare heterozygous variants as an unexplored source of diversity of phenotypic traits and diseases.     

Amide derivatives of 9,11-seco-estra-1,3,5(10)-trien-11-oic acid as modified orally active estrogen agonists with moderate antagonistic activity

Synthesis of amide derivatives of 9,11-seco-estra-1,3,5(10)-trien-11-oic acid containing alkyl and aromatic amine residues has been carried out with an aim to prepare orally active estrogen antagonists. Modification of the estradiol molecule in the form of C-seco-amide derivatives has led to their high oral absorption. Compounds 7 an n-propyl amide, 8 an n-butyl amide, and 16 a p-anisidyl amide of C-seco-estrane showed significant estrogen antagonistic activity (>20%), while, the majority of compounds possessed high estrogen agonistic activity on oral administration at 10mg/kg dose in rats.     

Cryptococcus gattii: a resurgent fungal pathogen

Cryptococcus gattii and Cryptococcus neoformans are causal agents of cryptococcosis, which manifests as pneumonia and meningitis. C. gattii has recently received widespread attention owing to outbreaks in British Columbia, Canada and the US Pacific Northwest. The biology of this tree-dwelling yeast is relatively unexplored, and there are few clues about how it causes infections in humans and animals. In this review, we summarize recent discoveries about C. gattii genetics and its ecological niche and highlight areas ripe for future exploration. Increased focus on epidemiology, ecological modeling and host-pathogen interactions is expected to yield a better understanding of this enigmatic yeast, and ultimately lead to better measures for its control.     

Temporal genetic stability in natural populations of the waterflea Daphnia magna in response to strong selection pressure

Studies monitoring changes in genetic diversity and composition through time allow a unique understanding of evolutionary dynamics and persistence of natural populations. However, such studies are often limited to species with short generation times that can be propagated in the laboratory or few exceptional cases in the wild. Species that produce dormant stages provide powerful models for the reconstruction of evolutionary dynamics in the natural environment. A remaining open question is to what extent dormant egg banks are an unbiased representation of populations and hence of the species’ evolutionary potential, especially in the presence of strong environmental selection. We address this key question using the water flea Daphnia magna, which produces dormant stages that accumulate in biological archives over time. We assess temporal genetic stability in three biological archives, previously used in resurrection ecology studies showing adaptive evolutionary responses to rapid environmental change. We show that neutral genetic diversity does not decline with the age of the population and it is maintained in the presence of strong selection. In addition, by comparing temporal genetic stability in hatched and unhatched populations from the same biological archive, we show that dormant egg banks can be consulted to obtain a reliable measure of genetic diversity over time, at least in the multidecadal time frame studied here. The stability of neutral genetic diversity through time is likely mediated by the buffering effect of the resting egg bank.     

Pichia cecembensis sp. nov. isolated from a papaya fruit (Carica papaya L., Caricaceae)

The ascogenous yeast YS16T was isolated from a decaying papaya fruit. Phenotypic traits such as multilateral budding, spheroidal or elongate shape, pseudohyphae formation, asci with one or more ascospores, ability to ferment d-glucose, inability to assimilate nitrate and the presence of Q7 ubiquinone suggest its affiliation to the genus Pichia. The nearest phylogenetic neighbor, based on D1/D2 domain sequence of the 26S rRNA gene and ITS region sequence, was identified as Issatchenkia orientalis (NRRL Y-5396T, a synonym of Pichia kudriavzevii) with similarities of 98.2% and 97% respectively. In addition to the difference in the D1/D2 and ITS region sequence, YS16T differs from I. orientalis with respect to a number of phenotypic traits. However, in the phylogenetic analysis, YS16T showed close relatedness to the P. membranifaciens clade. Thus, it is proposed to assign the status of a new species to YS16T, for which the name P. cecembensis sp. nov. is proposed. The type strain of P. cecembensis sp. nov. is YS16T (=NRRL Y-27985T=JCM 13873T=CBS 10445T).     

p90 Ribosomal S6 Kinase 1 (RSK1) and the Catalytic Subunit of Protein Kinase A (PKA) Compete for Binding the Pseudosubstrate Region of PKAR1��: ROLE IN THE REGULATION OF PKA AND RSK1 ACTIVITIES*

Previously we showed that the inactive form of p90 ribosomal S6 kinase 1 (RSK1) interacts with the regulatory subunit, PKARIα, of protein kinase A (PKA), whereas the active RSK1 interacts with the catalytic subunit (PKAc) of PKA. Herein, we demonstrate that the N-terminal kinase domain (NTK) of RSK1 is necessary for interactions with PKARIα. Substitution of the activation loop phosphorylation site (Ser-221) in the NTK with the negatively charged Asp residue abrogated the association between RSK1 and PKARIα. This explains the lack of an interaction between active RSK1 and PKARIα. Full-length RSK1 bound to PKARIα with an affinity of 0.8 nm. The NTK domain of RSK1 competed with PKAc for binding to the pseudosubstrate region (amino acids 93–99) of PKARIα. Overexpressed RSK1 dissociated PKAc from PKARIα, increasing PKAc activity, whereas silencing of RSK1 increased PKAc/PKARIα interactions and decreased PKAc activity. Unlike PKAc, which requires Arg-95 and -96 in the pseudosubstrate region of PKARIα for their interactions, RSK1/PKARIα association requires all four Arg residues (Arg-93–96) in the pseudosubstrate site of PKARIα. A peptide (Wt-PS) corresponding to residues 91–99 of PKARIα competed for binding of RSK1 with PKARIα both in vitro and in intact cells. Furthermore, peptide Wt-PS (but not control peptide Mut-PS), by dissociating RSK1 from PKARIα, activated RSK1 in the absence of any growth factors and protected cells from apoptosis. Thus, by competing for binding to the pseudosubstrate region of PKARIα, RSK1 regulates PKAc activity in a cAMP-independent manner, and PKARIα by associating with RSK1 regulates its activation and its biological functions.