Rapid coral colonization of a recent lava flow following a volcanic eruption,Banda Islands,Indonesia

Compared to the catastrophic impacts of various environmental disturbances and the subsequent recovery of scleractinian coral communities from these events, little is known about the early successional dynamics of coral communities following major volcanic eruptions. The 1988 volcanic eruption of Gunung Api, Banda Islands, Indonesia, provided a unique opportunity to study the rate at which a reef-building coral community develops on an andesitic lava flow. Coral colonization was studied at three locations varying in substrate characteristics. Five years after the eruption, the sheltered lava flow supported a diverse coral community (124 species) with high coral cover . Tabulate acroporids were a dominant component of the lava flow coral community, with some colonies measuring over 90 cm in diameter. Higher average coral diversity, coral abundance and cover were recorded on the andesitic lava flow than on an adjacent carbonate reef not covered by the lava, and on a substrate of unstable pyroclastic deposits located on the southwestern coast of the volcano. In some areas of high coral diversity and environmental stability, andesitic lava flows may create local hot-spots of coral diversity by providing a structurally complex, predator-free and stable substrate for the recruitment of coral species from the adjacent and regional species pools.     

Clusters in social behaviour of female domestic cats (Felis silvestris catus) living in confinement

Associations between different agonistic and affiliative behavioural patterns of female domestic cats (Felis silvestris catus) were studied. In three groups of intact cats living in confinement frequencies of fourteen agonistic and affiliative behavioural patterns were recorded. The technique of factor analysis (Principal Components Analysis followed by varimax rotation on a dyads X behavioural patterns matrix) was used to detect clusters in these behavioural patterns. Five factors (or types of interindividual relationships) were extracted per group. They accounted collectively for at least 77% of the total variance present in the data. Although differences existed between groups with respect to behavioural patterns included in each factor, four clusters of behaviours could be discriminated: (I) social rubbing, lordosis and rolling in front of partner (sexual behaviour), (II) allogrooming, social sniffing, nosing, sniffing rear and treading (inspection-affiliative behaviour), (III) offensive behaviour and staring, and (IV) defensive behaviour and staring. The role of these clusters in group living is discussed.     

Daphnids respond to algae-associated odours

Using a Y-tube olfactometer, it was found that Daphnia galeatax hyalina moves to the arm with odour from either of two ediblealgal species (Scenedesmus acuminatus and Oscillatoria limnetica)rather than to the alternative arm with clean water. However,no differential response was observed when odours of the toxiccyanobacterium (Oscillatoria agardhu) were tested. We suggestthat odours associated with edible algae attract Daphnia whereasnon-edible algae do not elicit attraction of Daphnia.     

An exogalacturonase from Aspergillus aculeatus able to degrade xylogalacturonan

Summary A pectic polysaccharide from soy was degraded by a crude extracellular preparation of Aspergillus aculeatus. Besides monomeric sugars, an unknown oligosaccharide was produced, which was purified and identified as the dimer -Xyl _p -(1,3)-GalA _p . The enzyme responsible for the release of this dimer was purified and characterized as an exogalacturonase, which was not hindered by side-chains of xylose.     

Effect of the redox state of QB on electric field-induced charge recombination in Photosystem II

Electric field-induced charge recombination in Photosystem II (PS II) was studied in osmotically swollen spinach chloroplasts (blebs) by measurement of the concomitant chlorophyll luminescence emission (electroluminescence). A pronounced dependence on the redox state of the two-electron gate Q_B was observed and the earlier failure to detect it is explained. The influence of the Q_B/Q_B ^– oscillation on electroluminescence was dependent on the redox state of the oxygen evolving complex; at times around one millisecond after flash illumination a large effect was observed in the states S₂ and S₃, but not in the state S₄ (actually Z⁺S₃). The presence of the oxidized secondary electron donor, tyrosine Z⁺, appeared to prevent expression of the Q_B/Q_B ^– effect on electroluminescence, possibly because this effect is primarily due to a shift of the redox equilibrium between Z/Z⁺ and the oxygen evolving complex.Abbreviations BSA bovine serum albumin - EDTA ethylene-diaminetetraacetic acid - EL electroluminescence - FCCP carbonylcyanide p-trifluoromethyloxyphenyl-hydrazone - HEPESI 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - I primary electron acceptor - MOPS 3-(N-morpholino) propane sulfonic acid - P680 primary electron donor of Photosystem II - P700 primary electron donor of Photosystem I - Q_A and Q_B secondary and tertiary electron acceptors of Photosystem II - Z secondary electron donor (D1 Tyr 161)     

Cold requirement for maximal activity of the bacterial ice nucleation protein INAZ in transgenic plants

The bacterial ice nucleation gene inaZ confers production of ice nuclei when transferred into transgenic plants. Conditioning of the transformed plant tissue at temperatures near 0°C greatly increased the ice nucleation activity in plants, and maximum ice nucleation activity was achieved only after low-temperature conditioning for about 48 h. Although the transgenic plants contain similar amounts of inaZ mRNA at both normal and low temperatures, low temperatures are required for accumulation of INAZ protein. We propose that the stability of the INAZ protein and thus ice nucleation activity in the transgenic plants is enhanced by low-temperature conditioning.     

The C-terminal KDEL sequence increases the expression level of a single-chain antibody designed to be targeted to both the cytosol and the secretory pathway in transgenic tobacco

The effects of subcellular localization on single-chain antibody (scFv) expression levels in transgenic tobacco was evaluated using an scFv construct of a model antibody possessing different targeting signals. For translocation into the secretory pathway a secretory signal sequence preceded the scFv gene (scFv-S). For cytosolic expression the scFv antibody gene lacked such a signal sequence (scFv-C). Also, both constructs were provided with the endoplasmic reticulum (ER) retention signal KDEL (scFv-SK and scFv-CK, respectively). The expression of the different scFv constructs in transgenic tobacco plants was controlled by a CaMV 35S promoter with double enhancer. The scFv-S and scFv-SK antibody genes reached expression levels of 0.01% and 1% of the total soluble protein, respectively. Surprisingly, scFv-CK transformants showed considerable expression of up to 0.2% whereas scFv-C transformants did not show any accumulation of the scFv antibody. The differences in protein expression levels could not be explained by the steady-state levels of the mRNAs. Transient expression assays with leaf protoplasts confirmed these expression levels observed in transgenic plants, although the expression level of the scFv-S construct was higher. Furthermore, these assays showed that both the secretory signal and the ER retention signal were recognized in the plant cells. The scFv-CK protein was located intracellularly, presumably in the cytosol. The increase in scFv protein stability in the presence of the KDEL retention signal is discussed.     

G2 arrest and impaired nucleocytoplasmic transport in mouse embryos lacking the proto-oncogene CAN/Nup214.

The vertebrate nucleopore complex (NPC) is a 125 MDa multiprotein assembly that mediates nucleocytoplasmic transport. One of its components, CAN/Nup214, is an FXFG repeat-containing protein known to be involved in myeloid leukemia in humans. We have devised a powerful genetic approach, using maternally derived protein in murine null embryos, to show that CAN/ Nup214 is essential for NPC function in vivo. We demonstrate that CAN-/- mouse embryonic stem (ES) cells are not viable and that CAN-/- embryos die in utero between 4.0 and 4.5 days postcoitum, following the depletion of their CAN from maternal sources. In 3.5-day-old mutant embryos, cultured in vitro, progressive depletion of CAN leads to cell cycle arrest in G2 phase, and eventually to blastocoel collapse, impaired NLS-mediated protein uptake and nuclear accumulation of polyadenylated RNA. Remarkably, these defective CAN-depleted embryos do not display any gross morphological abnormalities in their nuclear envelopes or NPCs. Our data suggest that CAN is critical to cell cycle progression and required for both nuclear protein import and mRNA export.     

Functional analysis of the interaction between the small GTP binding protein Cdc42 and the Ste20 protein kinase in yeast.

STE20 encodes a protein kinase related to mammalian p65Pak which functions in several signal transduction pathways in yeast, including those involved in pseudohyphal and invasive growth, as well as mating. In addition, Ste20 plays an essential role in cells lacking Cla4, a kinase with significant homology to Ste20. It is not clear how the activity of Ste20 is regulated in response to these different signals in vivo, but it has been demonstrated recently that binding of the small GTP binding protein Cdc42 is able to activate Ste20 in vitro. Here we show that Ste20 functionally interacts with Cdc42 in a GTP-dependent manner in vivo: Ste20 mutants that can no longer bind Cdc42 were unable to restore growth of ste20 cla4 mutant cells. They were also defective for pseudohyphal growth and agar invasion, and displayed reduced mating efficiency when mated with themselves. Surprisingly, however, the kinase activity of such Ste20 mutants was normal when assayed in vitro. Furthermore, these alleles were able to fully activate the MAP kinase pathway triggered by mating pheromones in vivo, suggesting that binding of Cdc42 and Ste20 was not required to activate Ste20. Wild-type Ste20 protein was visualized as a crescent at emerging buds during vegetative growth and at shmoo tips in cells arrested with alpha-factor. In contrast, a Ste20 mutant protein unable to bind Cdc42 was found diffusely throughout the cytoplasm, suggesting that Cdc42 is required to localize Ste20 properly in vivo.     

Distinct DNA sequence and structure requirements for the two steps of V(D)J recombination signal cleavage.

Cleavage of V(D)J recombination signals by purified RAG1 and RAG2 proteins permits the dissection of DNA structure and sequence requirements. The two recognition elements of a signal (nonamer and heptamer) are used differently, and their cooperation depends on correct helical phasing. The nonamer is most important for initial binding, while efficient nicking and hairpin formation require the heptamer sequence. Both nicking and hairpin formation are remarkably tolerant of variations in DNA structure. Certain flanking sequences inhibit hairpin formation, but this can be bypassed by base unpairing, and even a completely single-stranded signal sequence is well utilized. We suggest that DNA unpairing around the signal-coding border is essential for the initiation of V(D)J combination.