Canopy interactions and physical stress gradients in subtidal communities

Species interactions are integral drivers of community structure and can change from competitive to facilitative with increasing environmental stress. In subtidal marine ecosystems, however, interactions along physical stress gradients have seldom been tested. We observed seaweed canopy interactions across depth and latitudinal gradients to test whether light and temperature stress structured interaction patterns. We also quantified interspecific and intraspecific interactions among nine subtidal canopy seaweed species across three continents to examine the general nature of interactions in subtidal systems under low consumer pressure. We reveal that positive and neutral interactions are widespread throughout global seaweed communities and the nature of interactions can change from competitive to facilitative with increasing light stress in shallow marine systems. These findings provide support for the stress gradient hypothesis within subtidal seaweed communities and highlight the importance of canopy interactions for the maintenance of subtidal marine habitats experiencing environmental stress.     

New Approaches for Absolute Quantification of Stable‐Isotope‐Labeled Peptide Standards for Targeted Proteomics Based on a UV Active Tag

Targeted proteomics depends on the availability of stable isotope labeled (SIL) peptide standards, which for absolute protein quantification need to be absolutely quantified. In the present study, three new approaches for absolute quantification of SIL peptides are developed. All approaches rely on a quantification tag (Qtag) with a specific UV absorption. The Qtag is attached to the peptide during synthesis and is removed by tryptic digestion under standard proteomics workflow conditions. While one quantification method (method A) is designed to allow the fast and economic production of absolutely quantified SIL peptides, two other methods (methods B and C) are developed to enable the straightforward re‐quantification of SIL peptides after reconstitution to control and monitor known problems related to peptide solubility, precipitation, and adhesion to vials. All methods yield consistent results when compared to each other and when compared to quantification by amino acid analysis. The precise quantitation methods are used to characterize the in vivo specificity of the H3 specific histone methyltransferase EZH2.     

The plant homeodomain finger protein MESR4 is essential for embryonic development in Drosophila

Misexpression Suppressor of Ras 4 (MESR4), a plant homeodomain (PHD) finger protein with nine zinc‐finger motifs has been implicated in various biological processes including the regulation of fat storage and innate immunity in Drosophila. However, the role of MESR4 in the context of development remains unclear. Here it is shown that MESR4 is a nuclear protein essential for embryonic development. Immunostaining of polytene chromosomes using anti‐MESR4 antibody revealed that MESR4 binds to numerous bands along the chromosome arms. The most intense signal was detected at the 39E‐F region, which is known to contain the histone gene cluster. P‐element insertions in the MESR4 locus, which were homozygous lethal during embryogenesis with defects in ventral ectoderm formation and head encapsulation was identified. In the mutant embryos, expression of Fasciclin 3 (Fas3), an EGFR signal target gene was greatly reduced, and the level of EGFR signal‐dependent double phosphorylated ERK (dp‐ERK) remained low. However, in the context of wing vein formation, genetic interaction experiments suggested that MESR4 is involved in the EGFR signaling as a negative regulator. These results suggested that MESR4 is a novel chromatin‐binding protein required for proper expression of genes including those regulated by the EGFR signaling pathway during development. genesis 53:701–708, 2015. © 2015 Wiley Periodicals, Inc.     

Pollination by deceit in Paphiopedilum barbigerum (Orchidaceae): a staminode exploits the innate colour preferences of hoverflies (Syrphidae)

Paphiopedilum barbigerum T. Tang et F. T. Wang, a slipper orchid native to southwest China and northern Vietnam, produces deceptive flowers that are self‐compatible but incapable of mechanical self‐pollination (autogamy). The flowers are visited by females of Allograpta javana and Episyrphus balteatus (Syrphidae) that disperse the orchid’s massulate pollen onto the receptive stigmas. Measurements of insect bodies and floral architecture show that the physical dimensions of these two fly species correlate with the relative positions of the receptive stigma and dehiscent anthers of P. barbigerum. These hoverflies land on the slippery centralised wart located on the shiny yellow staminode and then fall backwards through the labellum entrance. They are temporarily trapped in the inflated chamber composed of the interconnected labellum and column. The attractive staminode of P. barbigerum strongly reflects the colour yellow (500–560 nm), a colour preferred innately by most pollen‐eating members of the Syrphidae. No scent molecules were detected using GC mass spectrometry analysis, showing that the primary attractant in this system is visual, not olfactory. Pollination‐by‐deceit in P. barbigerum is contrasted with its congener, P. dianthum, a brood site mimic that is pollinated by ovipositing females of E. balteatus. As the natural rate of fruit set in P. barbigerum (mean 26.3% pooled over three seasons) is lower than that of P. dianthum (mean 58.5% over two seasons), the evolution of false brood sites in some Paphiopedilum spp. should be selectively advantageous as they may provide an increase in the attention and return rates of dependable pollinators to flowers that always lack a reward.     

GENETIC VARIABILITY AND MOLECULAR PHYLOGENY OF DINOPHYSIS SPECIES (DINOPHYCEAE) FROM NORWEGIAN WATERS INFERRED FROM SINGLE CELL ANALYSES OF rDNA1

The objectives of this study were to determine rDNA sequences of the most common Dinophysis species in Scandinavian waters and to resolve their phylogenetic relationships within the genus and to other dinoflagellates. A third aim was to examine the intraspecific variation in D. acuminata and D. norvegica, because these two species are highly variable in both morphology and toxicity. We obtained nucleotide sequences of coding (small subunit [SSU], partial large subunit [LSU], 5.8S) and noncoding (internal transcribed spacer [ITS]1, ITS2) parts of the rRNA operon by PCR amplification of one or two Dinophysis cells isolated from natural water samples. The three photosynthetic species D. acuminata, D. acuta, and D. norvegica differed in only 5 to 8 of 1802 base pairs (bp) within the SSU rRNA gene. The nonphotosynthetic D. rotundata (synonym Phalacroma rotundatum[Claparède et Lachmann] Kofoid et Michener), however, differed in approximately 55 bp compared with the three photosynthetic species. In the D1 and D2 domains of LSU rDNA, the phototrophic species differed among themselves by 3 to 12 of 733 bp, whereas they differed from D. rotundata by more than 100 bp. This supports the distinction between Dinophysis and Phalacroma. In the phylogenetic analyses based on SSU rDNA, all Dinophysis species were grouped into a common clade in which D. rotundata diverged first. The results indicate an early divergence of Dinophysis within the Dinophyta. The LSU phylogenetic analyses, including 4 new and 11 Dinophysis sequences from EMBL, identified two major clades within the phototrophic species. Little or no intraspecific genetic variation was found in the ITS1–ITS2 region of single cells of D. norvegica and D. acuminata from Norway, but the delineation between these two species was not always clear.