Copper stress targets the rcs system to induce multiaggregative behavior in a copper-sensitive Salmonella strain

Salmonella ΔcuiD strains form mucoid colonies on copper-containing solid media. We show here that this multiaggregative behavior is caused by the Rcs-dependent induction of colanic acid extracellular polysaccharide. Deletion of cps operon genes in a ΔcuiD strain increased the sensitivity to copper, indicating a role for colanic acid in copper resistance.     

Nitrogen fixation rates in algal turf communities of a degraded versus less degraded coral reef

Algal turf communities are ubiquitous on coral reefs in the Caribbean and are often dominated by N₂-fixing cyanobacteria. However, it is largely unknown (1) how much N₂ is actually fixed by turf communities and (2) which factors affect their N₂ fixation rates. Therefore, we compared N₂ fixation activity by turf communities at different depths and during day and night-time on a degraded versus a less degraded coral reef site on the island of Curaçao. N₂ fixation rates measured with the acetylene reduction assay were slightly higher in shallow (5–10-m depth) than in deep turf communities (30-m depth), and N₂ fixation rates during the daytime significantly exceeded those during the night. N₂ fixation rates by the turf communities did not differ between the degraded and less degraded reef. Both our study and a literature survey of earlier studies indicated that turf communities tend to have lower N₂ fixation rates than cyanobacterial mats. However, at least in our study area, turf communities were more abundant than cyanobacterial mats. Our results therefore suggest that turf communities play an important role in the nitrogen cycle of coral reefs. N₂ fixation by turfs may contribute to an undesirable positive feedback that promotes the proliferation of algal turf communities while accelerating coral reef degradation.     

The binding protein BiP attenuates stress-induced cell death in soybean via modulation of the N-rich protein-mediated signaling pathway

The molecular chaperone binding protein (BiP) participates in the constitutive function of the endoplasmic reticulum (ER) and protects the cell against stresses. In this study, we investigated the underlying mechanism by which BiP protects plant cells from stress-induced cell death. We found that enhanced expression of BiP in soybean (Glycine max) attenuated ER stress- and osmotic stress-mediated cell death. Ectopic expression of BiP in transgenic lines attenuated the leaf necrotic lesions that are caused by the ER stress inducer tunicamycin and also maintained shoot turgidity upon polyethylene glycol-induced dehydration. BiP-mediated attenuation of stress-induced cell death was confirmed by the decreased percentage of dead cell, the reduced induction of the senescence-associated marker gene GmCystP, and reduced DNA fragmentation in BiP-overexpressing lines. These phenotypes were accompanied by a delay in the induction of the cell death marker genes N-RICH PROTEIN-A (NRP-A), NRP-B, and GmNAC6, which are involved in transducing a cell death signal generated by ER stress and osmotic stress through the NRP-mediated signaling pathway. The prosurvival effect of BiP was associated with modulation of the ER stress- and osmotic stress-induced NRP-mediated cell death signaling, as determined in transgenic tobacco (Nicotiana tabacum) lines with enhanced (sense) and suppressed (antisense) BiP levels. Enhanced expression of BiP prevented NRP- and NAC6-mediated chlorosis and the appearance of senescence-associated markers, whereas silencing of endogenous BiP accelerated the onset of leaf senescence mediated by NRPs and GmNAC6. Collectively, these results implicate BiP as a negative regulator of the stress-induced NRP-mediated cell death response.     

Larval and juvenile Pacific herring Clupea pallasii are not susceptible to infectious hematopoietic necrosis under laboratory conditions

Infectious hematopoietic necrosis (IHN) leads to periodic epidemics among certain wild and farmed fish species of the Northeast (NE) Pacific. The source of the IHN virus (IHNV) that initiates these outbreaks remains unknown; however, a leading hypothesis involves viral persistence in marine host species such as Pacific herring Clupea pallasii. Under laboratory conditions we exposed specific pathogen-free (SPF) larval and juvenile Pacific herring to 10(3) to 10(4) plaque-forming units (pfu) of IHNV ml(-1) by waterborne immersion. Cumulative mortalities among exposed groups were not significantly different from those of negative control groups. After waterborne exposure, IHNV was transiently recovered from the tissues of larvae but absent in tissues of juveniles. Additionally, no evidence of viral shedding was detected in the tank water containing exposed juveniles. After intraperitoneal (IP) injection of IHNV in juvenile herring with 10(3) pfu, IHNV was recovered from the tissues of sub-sampled individuals for only the first 5 d post-exposure. The lack of susceptibility to overt disease and transient levels of IHNV in the tissues of exposed fish indicate that Pacific herring do not likely serve a major epizootiological role in perpetuation of IHNV among free-ranging sockeye salmon Oncorhynchus nerka and farmed Atlantic salmon Salmo salar in the NE Pacific.     

Efficacy of several insecticides alone and with horticultural mineral oils on light brown apple moth (Lepidoptera: Tortricidae) eggs

The aim of the research was to identify efficacious and less environmentally harmful treatments than the standard chlorpyrifos sprays used for the control light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), eggs on nursery stock. A series of dip experiments showed a range of responses when comparing the efficacy of insecticides on egg hatch of E. postvittana. The insecticides that compared most favorably with chlorpyrifos were lamda-cyhalothrin and gamma-cyhalothrin, and thiacloprid. Indoxacarb, novaluron, and spinosad caused significant mortality only when combined with All Seasons mineral oil. All Seasons, showed ovicidal properties when evaluated alone and demonstrated adjuvant properties when combined with the above-mentioned insecticides, except gamma-cyhalothrin and thiacloprid. Several other horticultural mineral oils performed similarly, except the efficacy of spinosad varied with the oil product used, suggesting that the oil type selected is important for some insecticide and oil combinations. Several insecticides evaluated in this study are likely candidates for further work to develop treatments against E. postvittana eggs on nursery plants. Mineral oils are ovicidal and combinations with insecticides are likely to be advantageous.     

Fitness consequences of altering floral circadian oscillations for Nicotiana attenuata

Ecological interactions between flowers and pollinators are all about timing.Flower opening/closing and scent emissions are largely synchronized with pollinator activity,and a circadian clock regulates these rhythms.However,whether the circadian clock increases a plant's reproductive success by regulating these floral rhythms remains untested.Flowers of Nicotiana attenuata,a wild tobacco,diurnally and rhythmically open,emit scent and move vertically through a 140° arc to interact with nocturnal hawkmoths.We tethered flowers to evaluate the importance of flower positions for Manduca sexta-mediated pollinations;flower position dramatically influenced pollination.We examined the pollination success of phase-shifted flowers,silenced in circadian clock genes,NaZTL,NaLHY,and NaTOCi,by RNAi.Circadian rhythms in N.attenuata flowers are responsible for altered seed set from outcrossed pollen.     

Nuclear magnetic resonance solution structure of PisI, a group B immunity protein that provides protection against the type IIa bacteriocin piscicolin 126, PisA

Lactic acid bacteria produce and secrete bacteriocins. These bacteriocins are potent antimicrobial peptides that are active against other closely related bacteria. As a means of self-protection, producer organisms also express immunity proteins. Immunity proteins are generally located on the same genetic locus and are cotranscribed with the bacteriocin. Although some cross immunity between bacteriocins has been observed, immunity proteins are typically highly specific. Immunity proteins for the type IIa bacteriocins range from 81 to 115 amino acids in length and display substantial variation in their sequences. Nonetheless, such immunity proteins have been classified into three groupings (groups A, B, and C) according to sequence homology. The structures of a group C (ImB2) and two group A (EntA-im and PedB) immunity proteins have previously been reported. We herein report the nuclear magnetic resonance solution structure of the remaining class of the type IIa immunity proteins. PisI, a 98-amino acid protein, is a group B immunity protein conferring immunity against piscicolin 126 (PisA). Like ImB2, EntA-im, and PedB, PisI folds into a globular protein in aqueous solution and contains an antiparallel four-helix bundle. Compared to ImB2 and EntA-im, PisI has a substantially longer and more flexible N-terminus, but a shorter C-terminus. No direct interaction between the bacteriocin and immunity protein is observed by NMR in either aqueous or membrane mimicking environments. This further suggests that the mechanism that mediates immunity is not due to a direct bacteriocin-immunity protein interaction but rather is receptor-mediated. It has now been confirmed that the four-helix bundle is indeed a structural motif among the type IIa immunity proteins.     

Sequence analysis of WIS-2-1A,a retrotransposon-like element from wheat

WIS-2-1A, a 8624 bp insertion in the Glu-1A-2 locus of chromosome 1A of wheat, consists of two 1755 bp long terminal repeats enclosing a 5114 bp internal region. No long open reading frames could be found, but inspection of the predicted amino acid sequence showed regions with homology to retrotransposon structures, including a methionine tRNA initiator binding site, a nucleotide binding domain, a protease, an integrase and a polymerase. DNA replication errors have resulted in frame-shifts in the protein coding region, suggesting that retrotransposition of WIS-2-1A, if it occurs, must be mediated by trans-acting factors.     

Suppression of CD4+ T lymphocyte effector functions by CD4+CD25+ cells in vivo

CD4+CD25+ regulatory T cells have been extensively studied during the last decade, but how these cells exert their regulatory function on pathogenic effector T cells remains to be elucidated. Naive CD4+ T cells transferred into T cell-deficient mice strongly expand and rapidly induce inflammatory bowel disease (IBD). Onset of this inflammatory disorder depends on IFN-gamma production by expanding CD4+ T cells. Coinjection of CD4+CD25+ regulatory T cells protects recipient mice from IBD. In this study, we show that CD4+CD25+ regulatory T cells do not affect the initial activation/proliferation of injected naive T cells as well as their differentiation into Th1 effectors. Moreover, naive T cells injected together with CD4+CD25+ regulatory T cells into lymphopenic hosts are still able to respond to stimuli in vitro when regulatory T cells are removed. In these conditions, they produce as much IFN-gamma as before injection or when injected alone. Finally, when purified, they are able to induce IBD upon reinjection into lymphopenic hosts. Thus, prevention of IBD by CD4+CD25+ regulatory T cells is not due to deletion of pathogenic T cells, induction of a non reactive state (anergy) among pathogenic effector T cells, or preferential induction of Th2 effectors rather than Th1 effectors; rather, it results from suppression of T lymphocyte effector functions, leading to regulated responses to self.