Linaria dalmatica invades south-facing slopes and less grazed areas in grazing-tolerant mixed-grass prairie

Identifying environments where invasive plants are most invasive is key to understanding causes of invasion and developing effective management strategies. In mixed-grass prairie, invasive plants are often successful in relatively wet, nitrogen-rich areas, and areas protected from grazing. Dalmatian toadflax, a common invader of mixed-grass prairie, can also be favored by high water and nitrogen availability, but is thought to be relatively unpalatable to cattle, and therefore favored by grazing. We used spatially-adjusted model selection techniques to quantify relationships between toadflax cover (measured using very high-resolution aerial imagery), and relative snow deposition (estimated with a blowing snow model), slope, aspect, soil texture, and grazing intensity (estimated by proximity to water tanks). Toadflax was common throughout the 400 ha study site, occurring in 742 of 1,861 images. Toadflax cover was high on steeper slopes, particularly those with southern aspects. These two topographic variables were more effective in explaining toadflax distribution than modeled snow deposition, suggesting that factors other than snow deposition cause toadflax invasion on south-facing slopes. Toadflax cover was also high in areas further from water tanks, indicating that grazing may inhibit toadflax invasion. More broadly, this result suggests that grazing can reduce invasion of even relatively unpalatable species in ecosystems with long evolutionary histories of grazing.     

Characterization of a 65 kDa NIF in the nuclear matrix of the monocot Allium cepa that interacts with nuclear spectrin‐like proteins

Plant cells have a well organized nucleus and nuclear matrix, but lack orthologues of the main structural components of the metazoan nuclear matrix. Although data is limited, most plant nuclear structural proteins are coiled‐coil proteins, such as the NIFs (nuclear intermediate filaments) in Pisum sativum that cross‐react with anti‐intermediate filament and anti‐lamin antibodies, form filaments 6–12 nm in diameter in vitro, and may play the role of lamins. We have investigated the conservation and features of NIFs in a monocot species, Allium cepa, and compared them with onion lamin‐like proteins. Polyclonal antisera against the pea 65 kDa NIF were used in 1D and 2D Western blots, ICM (imunofluorescence confocal microscopy) and IEM (immunoelectron microscopy). Their presence in the nuclear matrix was analysed by differential extraction of nuclei, and their association with structural spectrin‐like proteins by co‐immunoprecipitation and co‐localization in ICM. NIF is a conserved structural component of the nucleus and its matrix in monocots with M_r and pI values similar to those of pea 65 kDa NIF, which localized to the nuclear envelope, perichromatin domains and foci, and to the nuclear matrix, interacting directly with structural nuclear spectrin‐like proteins. Its similarities with some of the proteins described as onion lamin‐like proteins suggest that they are highly related or perhaps the same proteins.     

Cloning of the neurodegeneration gene drop-dead and characterization of additional phenotypes of its mutation

Mutations in the Drosophila gene drop-dead (drd) result in early adult lethality and neurodegeneration, but the molecular identity of the drd gene and its mechanism of action are not known. This paper describes the characterization of a new X-linked recessive adult-lethal mutation, originally called lot's wife (lwf(1)) but subsequently identified as an allele of drd (drd(lwf)); drd(lwf) mutants die within two weeks of eclosion. Through mapping and complementation, the drd gene has been identified as CG33968, which encodes a putative integral membrane protein of unknown function. The drd(lwf) allele is associated with a nonsense mutation that eliminates nearly 80% of the CG33968 gene product; mutations in the same gene were also found in two previously described drd alleles. Characterization of drd (lwf) flies revealed additional phenotypes of drd, most notably, defects in food processing by the digestive system and in oogenesis. Mutant flies store significantly more food in their crops and defecate less than wild-type flies, suggesting that normal transfer of ingested food from the crop into the midgut is dependent upon the DRD gene product. The defect in oogenesis results in the sterility of homozygous mutant females and is associated with a reduction in the number of vitellogenic egg chambers. The disruption in vitellogenesis is far more severe than that seen in starved flies and so is unlikely to be a secondary consequence of the digestive phenotype. This study demonstrates that mutation of the drd gene CG33968 results in a complex phenotype affecting multiple physiological systems within the fly.     

Photoinduced reactivity of the HIV-1 envelope glycoprotein with a membrane-embedded probe reveals insertion of portions of the HIV-1 Gp41 cytoplasmic tail into the viral membrane

The interactions of HIV-1 Env (gp120-gp41) with CD4 and coreceptors trigger a barrage of conformational changes in Env that drive the membrane fusion process. Various regions of gp41 have profound effects on HIV entry and budding. However, the precise interactions between gp41 and the membrane have not been elucidated. To examine portions of membrane proteins that are embedded in membrane lipids, we have studied photoinduced chemical reactions in membranes using the lipid bilayer specific probe iodonaphthyl azide (INA). Here we show that in addition to the transmembrane anchor, amphipatic sequences in the cytoplasmic tail (CT) of HIV-1 gp41 are labeled by INA. INA labeling of the HIV-1 gp41 CT was similar whether wild-type or a mutant HIV-1 was used with uncleaved p55 Gag, which does not allow entry. These results shed light on the disposition of the HIV-1 gp41 CT with respect to the membrane. Moreover, our data have general implications for topology of membrane proteins and their in situ interactions with the lipid bilayer.     

Bronchodilating properties of the prostaglandin F2β in the guinea pig and cat

The bronchodilating properties of PGF_2β (a stereo-isomer of the naturally occurring bronchoconstrictor (PGF_2α) are described in the guinea pig and cat. The possible physiologic implications of this finding are discussed.     

Effects of stress on human mating preferences: stressed individuals prefer dissimilar mates

Although humans usually prefer mates that resemble themselves, mating preferences can vary with context. Stress has been shown to alter mating preferences in animals, but the effects of stress on human mating preferences are unknown. Here, we investigated whether stress alters men''s preference for self-resembling mates. Participants first underwent a cold-pressor test (stress induction) or a control procedure. Then, participants viewed either neutral pictures or pictures of erotic female nudes whose facial characteristics were computer-modified to resemble either the participant or another participant, or were not modified, while startle eyeblink responses were elicited by noise probes. Erotic pictures were rated as being pleasant, and reduced startle magnitude compared with neutral pictures. In the control group, startle magnitude was smaller during foreground presentation of photographs of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to self-resembling mates. In the stress group, startle magnitude was larger during foreground presentation of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to dissimilar mates. Our findings show that stress affects human mating preferences: unstressed individuals showed the expected preference for similar mates, but stressed individuals seem to prefer dissimilar mates.     

Nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase of Neurospora. III. Inactivation by nitration of a tyrosine residue involved in coenzyme binding.

Neurospora glutamate dehydrogenase (NADP-specific) is rapidly inactivated upon reaction with tetranitromethane. This inactivation is completely prevented by the presence of coenzyme (NADP) or nicotinamide mononucleotide (NMN) but not by substrate. NADH, or 2'-monophosphoadenosine-5'-diphosphoribose. Amino acid analysis indicates that the primary effect of modification is nitration of a single residue of tyrosine per polypeptide chain. We have identified the reactive tyrosine by isolation of a single, uniquely labeled peptide after hydrolysis with trypsin followed by cleavage with cyanogen bromide. The modified residue proved to be tyrosine-168 in the linear sequence. This residue is not present in the part of the sequence that had been previously implicated as involved in the binding of the adenylate portion of the coenzyme. Both NMN and 2-monophosphoadenosine-5'-diphosphoribose act as competitive inhibitors of NADP in the oxidation of glutamate with Ki values of 4.65 x 10(-4) M and 4.30 x 10(-4) M, respectively. Thus, the specific protection afforded by NADP and NMN, but not by 2'-monophosphoadenosine-5'-diphosphoribose, indicates that tyrosine-168 is involved in binding the nicotinamide portion of the coenzyme.