Water-borne seed transport and seed deposition during flooding in a small river-valley in Northern Germany

Water-borne seed transport and seed deposition during flooding were studied in the Upper Eider river (N-Germany) by direct sampling of the rivers seed content with aquatic seed traps and by analysing the number of deposited seeds on sedimentation mats which were exposed near the river on the soil surface during a flooding period of approx. three weeks.The number of seeds which were transported at the surface of the river Eider was continuously analysed by four aquatic seed traps for a period of 20 weeks (July–December 2000). To test the capture rate of these traps, a recapture experiment with colour marked seeds of Helianthus annuus L. was carried out. During the investigation period approx. 9000 seeds of 76 species were captured by the four aquatic seed traps. The number of trapped seeds varied both spatially (across the river profile) and temporally. Considering this variation and the capture rate of the traps, the water-borne seed transport was estimated to be 3139 seeds per week and meter of the river profile.The seed deposition during a flood in early spring 2002 was analysed by using 20 sedimentation mats. To distinguish effects of seed dispersal into patches from outside from seed rearrangement within patches, the water-borne seed transport was excluded from one half of the mats by fencing them with a woven fabric which was permeable for water but not for floating seeds. Outside of the exclosures 152 viable seeds of 26 species were deposited on the sedimentation mats while only one single seedling was found on mats from which water-borne seed transport was excluded.The results demonstrate that hydrochorous dispersal processes might play an important role in connecting otherwise fragmented populations in periodically flooded habitats along rivers.     

Identification of a region of Escherichia coli DnaB required for functional interaction with DnaG at the replication fork

The fundamental activities of the replicative primosomes of Escherichia coli are provided by DnaB, the replication fork DNA helicase, and DnaG, the Okazaki fragment primase. As we have demonstrated previously, DnaG is recruited to the replication fork via a transient protein-protein interaction with DnaB. Here, using site-directed amino acid mutagenesis, we have defined the region on DnaB required for this protein-protein interaction. Mutations in this region of DnaB affect the DnaB-DnaG interaction during both general priming-directed and phiX174 complementary strand DNA synthesis, as well as at replication forks reconstituted in rolling circle DNA replication reactions. The behavior of the purified mutant DnaB proteins in the various replication systems suggests that access to the DnaG binding pocket on DnaB may be restricted at the replication fork.     

Origin and evolution of the RIG-I like RNA helicase gene family

Background  

The DExD/H domain containing RNA helicases such as retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are key cytosolic pattern recognition receptors (PRRs) for detecting nucleotide pathogen associated molecular patterns (PAMPs) of invading viruses. The RIG-I and MDA5 proteins differentially recognise conserved PAMPs in double stranded or single stranded viral RNA molecules, leading to activation of the interferon system in vertebrates. They share three core protein domains including a RNA helicase domain near the C terminus (HELICc), one or more caspase activation and recruitment domains (CARDs) and an ATP dependent DExD/H domain. The RIG-I/MDA5 directed interferon response is negatively regulated by laboratory of genetics and physiology 2 (LGP2) and is believed to be controlled by the mitochondria antiviral signalling protein (MAVS), a CARD containing protein associated with mitochondria.     

SERPINE2, a serine protease inhibitor extensively expressed in adult male mouse reproductive tissues, may serve as a murine sperm decapacitation factor

SERPINE2, one of the potent serine protease inhibitors that modulates the activity of plasminogen activator and thrombin, is implicated in many biological processes. In the present study, we purified SERPINE2 from mouse seminal vesicle secretion (SVS), using liquid chromatography and identified it by liquid chromatography/tandem mass spectrometry, and it showed potent inhibitory activity against the urokinase-type plasminogen activator. SERPINE2 was expressed predominantly in seminal vesicles among murine male reproductive tissues. It was immunolocalized to the SVS and mucosal epithelium of the seminal vesicle, epididymis, coagulating gland, and vas deferens. In the testes, SERPINE2 was immunostained in spermatogonia, spermatocytes, spermatids, Leydig cells, and spermatozoa. SERPINE2 was also detected on the acrosomal cap of testicular and epididymal sperm and was suggested to be an intrinsic sperm surface protein. The purified SERPINE2 protein could bind to epididymal sperm. A prominent amount of SERPINE2 was detected on ejaculated and oviductal spermatozoa. Nevertheless, SERPINE2 was detected predominantly on uncapacitated sperm, indicating that SERPINE2 is lost before initiation of the capacitation process. Moreover, SERPINE2 could inhibit in vitro bovine serum albumin-induced sperm capacitation and prevent sperm binding to the egg, thus blocking fertilization. It acts through preventing cholesterol efflux, one of the initiation events of capacitation, from the sperm. These findings suggest that the SERPINE2 protein may play a role as a sperm decapacitation factor.     

RNA interference of pheromone biosynthesis-activating neuropeptide receptor suppresses mating behavior by inhibiting sex pheromone production in Plutella xylostella (L.)

Sex pheromone production is regulated by pheromone biosynthesis-activating neuropeptide (PBAN) in many lepidopteran species. We cloned a PBAN receptor (Plx-PBANr) gene from the female pheromone gland of the diamondback moth, Plutella xylostella (L.). Plx-PBANr encodes 338 amino acids and has conserved structural motifs implicating in promoting G protein coupling and tyrosine-based sorting signaling along with seven transmembrane domains, indicating a typical G protein-coupled receptor. The expression of Plx-PBANr was found only in the pheromone gland of female adults among examined tissues and developmental stages. Heterologous expression in human uterus cervical cancer cells revealed that Plx-PBANr induced significant calcium elevation when challenged with Plx-PBAN. Female P. xylostella injected with double-stranded RNA specific to Plx-PBANr showed suppression of the receptor gene expression and exhibited significant reduction in pheromone biosynthesis, which resulted in loss of male attractiveness. Taken together, the identified PBAN receptor is functional in PBAN signaling via calcium secondary messenger, which leads to activation of pheromone biosynthesis and male attraction.     

Utility of the trnH–psbA Intergenic Spacer Region and Its Combinations as Plant DNA Barcodes: A Meta-Analysis

Background

The trnH–psbA intergenic spacer region has been used in many DNA barcoding studies. However, a comprehensive evaluation with rigorous sequence preprocessing and statistical testing on the utility of trnH–psbA and its combinations as DNA barcodes is lacking.

Methodology/Principal Findings

Sequences were searched from GenBank for a meta-analysis on the usefulness of trnH–psbA and its combinations as DNA barcodes. After preprocessing, we constructed full and matching data sets that contained 17 983 trnH–psbA sequences and 2190 sets of trnH–psbA, matK, rbcL, and ITS2 sequences from the same sample, repectively. These datasets were used to analyze the ability of trnH–psbA and its combinations to discriminate species by the BLAST and BLAST+P methods. The Fisher''s exact test was used to evaluate the significance of performance differences. For the full data set, the identification success rates of trnH–psbA exceeded 70% in 18 families and 12 genera, respectively. For the matching data set, the identification rates of trnH–psbA were significantly higher than those of the other loci in two families and four genera. Similarly, the identification rates of trnH–psbA+ITS2 were significantly higher than those of matK+rbcL in 18 families and 21 genera.

Conclusion/Significane

This study provides valuable information on the higher utility of trnH–psbA and its combinations. We found that trnH–psbA+ITS2 combination performs better or equally well compared with other combinations in most taxonomic groups investigated. This information will guide the optimal usage of trnH–psbA and its combinations for species identification.