EFFECT OF TEMPERATURE AND GRAZING ON GROWTH AND REPRODUCTION OF FLOATING MACROCYSTIS SPP. (PHAEOPHYCEAE) ALONG A LATITUDINAL GRADIENT1

Macroalgal rafts frequently occur floating in coastal waters of temperate regions of the world’s oceans. These rafts are considered important dispersal vehicles for associated organisms with direct development. However, environmental factors may limit the floating potential of kelp and thereby the dispersal of associated organisms. To examine the effect of water temperature and grazing on growth, reproductive output, and survival of floating Macrocystis spp., experiments were conducted in outdoor tanks during austral summer 2006/2007 at three sites along the Chilean Pacific coast (20° S, 30° S, 40° S). At each site, Macrocystis spp. was maintained individually at three different water temperatures (ambient, ambient − 4°C, ambient + 4°C) and in the presence or absence of the amphipod grazer Peramphithoe femorata for 14 d. High water temperatures (>20°C) provoked rapid degradation of Macrocystis spp. rafts. At moderate temperatures (15°C–20°C), algal survival depended on the presence of associated grazers. In the absence of grazers, algal rafts gained in biomass while grazing caused considerable losses of algal biomass. Algal survival was the highest under cooler conditions (<15°C), where raft degradation was slow and grazer-induced biomass losses were compensated by continuing algal growth. Our results indicate that floating kelp rafts can survive for long time periods at the sea surface, but survival depends on the interaction between temperature and grazing. We suggest that these processes limiting the survival of kelp rafts in warmer temperatures may act as a dispersal barrier for kelp and its associated passengers.     

PHYSIOLOGICAL PERFORMANCE OF FLOATING GIANT KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE): LATITUDINAL VARIABILITY IN THE EFFECTS OF TEMPERATURE AND GRAZING1

Rafts of Macrocystis pyrifera (L.) C. Agardh can act as an important dispersal vehicle for a multitude of organisms, but this mechanism requires prolonged persistence of floating kelps at the sea surface. When detached, kelps become transferred into higher temperature and irradiance regimes at the sea surface, which may negatively affect kelp physiology and thus their ability to persist for long periods after detachment. To examine the effect of water temperature and herbivory on the photosynthetic performance, pigment composition, carbonic anhydrase (CA) activity, and the nitrogen (N) and carbon (C) content of floating M. pyrifera, experiments were conducted at three sites (20° S, 30° S, 40° S) along the Chilean Pacific coast. Sporophytes of M. pyrifera were maintained at three different temperatures (ambient, ambient ? 4°C, ambient + 4°C) and in presence or absence of the amphipod Peramphithoe femorata for 14 d. CA activity decreased at 20° S and 30° S, where water temperatures and irradiances were highest. At both sites, pigment contents were substantially lower in the experimental algae than in the initial algae, an effect that was enhanced by grazers. Floating kelps at 20° S could not withstand water temperatures >24°C and sank at day 5 of experimentation. Maximal quantum yield decreased at 20° S and 30° S but remained high at 40° S. It is concluded that environmental stress is low for kelps floating under moderate temperature and irradiance conditions (i.e., at 40° S), ensuring their physiological integrity at the sea surface and, consequently, a high dispersal potential for associated biota.     

PI3K Inhibition Augments the Therapeutic Efficacy of a 3a-aza-Cyclopenta[α]indene Derivative in Lung Cancer Cells

The synergistic targeting of DNA damage and DNA repair is a promising strategy for the development of new chemotherapeutic agents for human lung cancer. The DNA interstrand cross-linking agent BO-1509, a derivative of 3a-aza-cyclopenta[α]indene, was synthesized and combined with the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 to treat human lung cancer cells. Our results showed that the BO-1509 and LY294002 combination synergistically killed lung cancer cells in culture and also suppressed the growth of lung cancer xenografts in mice, including those derived from gefitinib-resistant cells. We also found that LY294002 suppressed the induction of several DNA repair proteins by BO-1509 and inhibited the nuclear translocation of Rad51. On the basis of the results of the γH2AX foci formation assays, LY294002 apparently inhibited the repair of DNA damage that was induced by BO-1509. According to the complete blood profile, biochemical enzyme analysis, and histopathologic analysis of major organs, no apparent toxicity was observed in mice treated with BO-1509 alone or in combination with LY294002. Our results suggest that the combination of a DNA cross-linking agent with a PI3K inhibitor is a feasible strategy for the treatment of patients with lung cancer.     

Immunohistochemical expression of two members of the GDNF family of growth factors and their receptors in the olfactory system

The glial cell line-derived (GDNF) family of trophic factors, GDNF, neurturin, persephin and artemin, are known to support the survival and regulate differentiation of many neuronal populations, including peripheral autonomic, enteric and sensory neurons. Members of this family of related ligands bind to specific GDNF family receptor (GFR) proteins, which complex and signal through the Ret receptor tyrosine kinase. We showed previously that GDNF protein was detectable in olfactory sensory neurons (OSNs) in the olfactory neuroepithelium (ON). In this immunohistochemical study, we localized GDNF, neurturin, GFRα1, GFRα2 and Ret in the adult rat ON and olfactory bulb. We found that GDNF and Ret were widely expressed by immature and mature OSNs, while neurturin was selectively expressed in a subpopulation of OSNs zonally restricted in the ON. The GFRs had differential expression, with mature OSNs and their axons preferentially expressing GFRα1, whereas progenitors and immature neurons more avidly expressed GFRα2. In the bulb, GDNF was highly expressed by the mitral and tufted cells, and by periglomerular cells, and its distribution generally resembled that of Ret, with the exception that Ret was far more predominant on fibers than cell bodies. Neurturin, in contrast, was present at lower levels and was more restricted in its expression to the axonal compartment. GFRα2 appeared to be the dominant accessory protein in the bulb. These data are supportive of two members of this neurotrophic family, GDNF and neurturin, playing different physiological roles in the olfactory neuronal system.     

The variable routes of rafting: stranding dynamics of floating bull kelp Durvillaea antarctica (Fucales,Phaeophyceae) on beaches in the SE Pacific

Dispersal on floating seaweeds depends on availability, viability, and trajectories of the rafts. In the southern hemisphere, the bull kelp Durvillaea antarctica is one of the most common floating seaweeds, but phylogeographic studies had shown low connectivity between populations from continental Chile, which could be due to limitations in local supply and dispersal of floating kelps. To test this hypothesis, the spatiotemporal dynamics of kelp strandings were examined in four biogeographic districts along the Chilean coast (28°–42°S). We determined the biomass and demography of stranded individuals on 33 beaches for three subsequent years (2013, 2014, 2015) to examine whether rafting is restricted to certain districts and seasons (winter or summer). Stranded kelps were found on all beaches. Most kelps had only one stipe (one individual), although we also frequently found coalesced holdfasts with mature males and females, which would facilitate successful rafting dispersal, gamete release, and reproduction upon arrival. High biomasses of stranded kelps occurred in the northern‐central (30°S–33°S) and southernmost districts (37°S–42°S), and lower biomasses in the northernmost (28°S–30°S) and southern‐central districts (33°S–37°S). The highest percentages and sizes of epibionts (Lepas spp.), indicative of prolonged floating periods, were found on stranded kelps in the northernmost and southernmost districts. Based on these results, we conclude that rafting dispersal can vary regionally, being more common in the northernmost and southernmost districts, depending on intrinsic (seaweed biology) and extrinsic factors (shore morphology and oceanography) that affect local supply of kelps and regional hydrodynamics.     

Isolation and identification of N-mercapto-4-formylcarbostyril, an antibiotic produced by Pseudomonas fluorescens.

Pseudomonas fluorescens strain G308 isolated from barley leaves produces a novel antibiotic substance that was purified by preparative TLC and HPLC and identified as N-mercapto-4-formylcarbostyril (Cbs) by LC/DAD, IR, LC-ES(+)/MS, LC-ES(-)/MS, GC-EI/MS, LC-HRES(+)/MS, mass isotope ratios analysis, 1H NMR and 13C NMR analysis. The purified new antibiotic compound is effective against many phytopathogenic fungi in vitro. The compound inhibited at 25 ppm spore germination and germ tube growth of the following fungi; Fusarium oxysporum f. sp. lycopersici, Fusarium culmorum, Cladosporium cucumerinum and Colletotrichum lagenarium. At concentrations up to 125 ppm, the compound did not interfere with release of zoospores from sporangia and germination of encysted zoospores of Phytophthora infestans.     

ARED 2.0: an update of AU-rich element mRNA database

The Adenylate Uridylate (AU)-Rich Element Database, ARED-mRNA version 2.0, contains information not present in the previous ARED. This includes additional data entries, new information and links to Unigene, LocusLink, RefSeq records and mouse homologue data. An ARE consensus sequence specific to the 3'UTR is the basis of ARED that demonstrated two important findings: (i) AREs are present in a large, previously unrecognized set of human mRNAs; and (ii) ARE-mRNAs encode proteins of diverse functions which are largely involved in early and transient biological responses. In this update, we have modified the strategy for identifying ARE-mRNA in order to systematically deal with inconsistencies of molecule type and mRNA region in GenBank records. Potential uses for the ARED in functional genomics are also given. The database is accessible via the web, http://rc.kfshrc.edu.sa/ared, with a new querying system that allows searching ARE-mRNAs by any public database identifier or name. The ARED website also contains relevant links to uses for the ARED.