Search of the human proteome for endomorphin-1 and endomorphin-2 precursor proteins

Based on the promising opioid pharmacological profile of the peptide, Tyr-Pro-Trp-Gly-NH(2) (Tyr-W-MIF), Zadina et al. [Zadina, J.E., Hackler, L., Ge, L.-J., Kastin, A.J., 1997. A potent and selective endogenous agonist for the mu-opiate receptor. Nature 386, 499-5502] synthesized and screened other Gly(4)-substituted peptides, culminating in the synthesis of Tyr-Pro-Trp-Phe-NH(2) (endomorphin-1), which displayed high affinity and selectivity for the mu-opioid receptor. The amidated peptide was then isolated from bovine brain frontal cortex, as was a related peptide, Tyr-Pro-Phe-Phe-NH(2) (endomorphin-2), that displayed similar high affinity and selectivity for the mu-opioid receptor. The biosynthesis of the endomorphins in the brain remains obscure, since the putative precursor proteins for the peptides have not been identified. With the completion of the human genome sequencing project, we hypothesized that we should uncover the biological precursors of the peptides using a bioinformatic approach to search the current human proteome for proteins that contained the endomorphin peptide sequences followed by Gly-Lys/Arg, the consensus sequence for peptide alpha-amidation and precursor cleavage. Twelve proteins were identified that contained the endomorphin-1 Tyr-Pro-Trp-Phe sequence, however none contained the Tyr-Pro-Trp-Phe-Gly sequence necessary for alpha-amidation. Twenty-two distinct proteins contained the endomorphin-2 tetrapeptide sequence, and two of those contained the sequence, Tyr-Pro-Phe-Phe-Gly, however, none contained the requisite peptide-Gly-Lys/Arg sequence. Western blot analysis using an endomorphin-2 antibody detected 4 prominent proteins in mouse brain, necessitating reinterpretation of previous immunocytolocalization studies in the brain. Screening of the current human proteome yielded no evidence for endomorphin precursor proteins based on accepted biochemical criteria.     

Positive Effects of Nonnative Invasive Phragmites australis on Larval Bullfrogs

Background

Nonnative Phragmites australis (common reed) is one of the most intensively researched and managed invasive plant species in the United States, yet as with many invasive species, our ability to predict, control or understand the consequences of invasions is limited. Rapid spread of dense Phragmites monocultures has prompted efforts to limit its expansion and remove existing stands. Motivation for large-scale Phragmites eradication programs includes purported negative impacts on native wildlife, a view based primarily on observational results. We took an experimental approach to test this assumption, estimating the effects of nonnative Phragmites australis on a native amphibian.

Methodology/Principal Findings

Concurrent common garden and reciprocal transplant field experiments revealed consistently strong positive influences of Phragmites on Rana catesbeiana (North American bullfrog) larval performance. Decomposing Phragmites litter appears to contribute to the effect.

Conclusions/Significance

Positive effects of Phragmites merit further research, particularly in regions where both Phragmites and R. catesbeiana are invasive. More broadly, the findings of this study reinforce the importance of experimental evaluations of the effects of biological invasion to make informed conservation and restoration decisions.     

Population genetics of reef coral endosymbionts (Symbiodinium,Dinophyceae)

Symbiodinium is a diverse genus of unicellular dinoflagellate symbionts associating with various marine protists and invertebrates. Although the broadscale diversity and phylogenetics of the Symbiodinium complex is well established, there have been surprisingly few data on fine‐scale population structure and biogeography of these dinoflagellates. Yet population‐level processes contribute strongly to the biology of Symbiodinium, including how anthropogenic‐driven global climate change impacts these symbionts and their host associations. Here, we present a synthesis of population‐level characteristics for Symbiodinium, with an emphasis on how phylogenetic affinities, dynamics within and among host individuals, and a propensity towards clonality shape patterns on and across reefs. Major inferences include the following: (i) Symbiodinium populations within individual hosts are comprised mainly of cells belonging to a single or few genetic clones. (ii) Symbiont populations exhibit a mixed mode of reproduction, wherein at least one sexual recombination event occurs in the genealogy between most genotypes, but clonal propagation predominates overall. (iii) Mutualistic Symbiodinium do not perpetually persist outside their hosts, instead undergoing turnover and replacement via the continuous shedding of viable clonal cells from host individuals. (iv) Symbiont populations living in the same host, but on different reefs, are often genetically subdivided, suggesting low connectivity, adaptation to local conditions, or prolific asexual reproduction and low effective population sizes leading to disproportionate success within and among hosts. Overall, this synthesis forms a basis for future investigations of coral symbiosis ecology and evolution as well as delimitation of species boundaries in Symbiodinium and other eukaryotic microorganisms.     

Population collapse dynamics in Acropora downingi,an Arabian/Persian Gulf ecosystem‐engineering coral,linked to rising temperature

As in the tropical Atlantic, Acropora populations in the southern Persian/Arabian Gulf plummeted within two decades after having been ecosystem engineers on most wave‐exposed reefs since the Pleistocene. Since 1996/1998 live coral cover in the Gulf declined by over 90% in many areas, primarily due to bleaching and diseases caused by rising temperatures. In the formerly dominant table‐coral species A. downingi, population dynamics corresponding to disturbance regimes was quantified in three transition matrices (lower disturbance pre‐1996; moderate disturbance from 1998 to 2010 and 2013 to 2017, disturbed in 1996/1998, 2010/11/12, 2017). Increased disturbance frequency and severity caused progressive reduction in coral size, cover, and population fecundity. Small size‐classes were bolstered more by partial colony mortality than sexual recruitment. Some large corals had a size refuge and resisted die‐back but were also lost with increasing disturbance. Matrix and biophysical larval flow models suggested one metapopulation. Southern, Arabian, populations could be connected to northern, Iranian, populations but this connectivity was lost under assumptions of pelagic larval duration at rising temperatures shortened to a third. Then, the metapopulation disintegrated into isolated populations. Connectivity required to avoid extinctions increased exponentially with disturbance frequency and correlation of disturbances across the metapopulation. Populations became unsustainable at eight disturbances in 15 years, when even highest theoretical recruitment no longer compensated mortality. This lethal disturbance frequency was 3‐fold that of the moderately disturbed monitoring period and 4‐fold of the preceding low‐disturbance period—suggesting ongoing shortening of the disturbance‐free period. Observed population collapse and environmental changes in the Gulf suggest that A. downingi is heading toward at least functional extinction mainly due to increasingly frequent temperature‐induced mortality events, clearly linked to climate change.