Effect of plant root symbionts on performance of native woody species in competition with an invasive grass in multispecies microcosms

The majority of terrestrial plants form mutualistic associations with arbuscular mycorrhizal fungi (AMF) and rhizobia (i.e., nitrogen‐fixing bacteria). Understanding these associations has important implications for ecological theory and for restoration practice. Here, we tested whether the presence of AMF and rhizobia influences the performance of native woody plants invaded by a non‐native grass in experimental microcosms. We planted eight plant species (i.e., Acacia acuminata, A. microbotrya, Eucalyptus loxophleba subsp. loxophleba, E. astringens, Calothamnus quadrifidus, Callistemon phoeniceus, Hakea lissocarpha and H. prostrata) in microcosms of field‐conditioned soil with and without addition of AMF and rhizobia in a fully factorial experimental design. After seedling establishment, we seeded half the microcosms with an invasive grass Bromus diandrus. We measured shoot and root biomass of native plants and Bromus, and on roots, the percentage colonization by AMF, number of rhizobia‐forming nodules and number of proteaceous root clusters. We found no effect of plant root symbionts or Bromus addition on performance of myrtaceous, and as predicted, proteaceous species as they rely little or not at all on AMF and rhizobia. Soil treatments with AMF and rhizobia had a strong positive effect (i.e., larger biomass) on native legumes (A. microbotrya and A. acuminata). However, the beneficial effect of root symbionts on legumes became negative (i.e., lower biomass and less nodules) if Bromus was present, especially for one legume, i.e., A. acuminata, suggesting a disruptive effect of the invader on the mutualism. We also found a stimulating effect of Bromus on root nodule production in A. microbotrya and AMF colonization in A. acuminata which could be indicative of legumes’ increased resource acquisition requirement, i.e., for nitrogen and phosphorus, respectively, in response to the Bromus addition. We have demonstrated the importance of measuring belowground effects because the aboveground effects gave limited indication of the effects occurring belowground.     

Enhancer Activation by Pharmacologic Displacement of LSD1 from GFI1 Induces Differentiation in Acute Myeloid Leukemia

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Abnormal Compartmentalization of Cartilage Matrix Components in Mice Lacking Collagen X: Implications for Function

There are conflicting views on whether collagen X is a purely structural molecule, or regulates bone mineralization during endochondral ossification. Mutations in the human collagen α1(X) gene (COL10A1) in Schmid metaphyseal chondrodysplasia (SMCD) suggest a supportive role. But mouse collagen α1(X) gene (Col10a1) null mutants were previously reported to show no obvious phenotypic change. We have generated collagen X deficient mice, which shows that deficiency does have phenotypic consequences which partly resemble SMCD, such as abnormal trabecular bone architecture. In particular, the mutant mice develop coxa vara, a phenotypic change common in human SMCD. Other consequences of the mutation are reduction in thickness of growth plate resting zone and articular cartilage, altered bone content, and atypical distribution of matrix components within growth plate cartilage. We propose that collagen X plays a role in the normal distribution of matrix vesicles and proteoglycans within the growth plate matrix. Collagen X deficiency impacts on the supporting properties of the growth plate and the mineralization process, resulting in abnormal trabecular bone. This hypothesis would accommodate the previously conflicting views of the function of collagen X and of the molecular pathogenesis of SMCD.     

The Orientational Consequences of Flocking Behaviour in Homing Pigeons,Columba livia

Two experiments are described which investigate the orientational consequences of flocking in homing pigeons Columba livia. Previous experiments have shown that homing pigeons placed inside a clear-sided release box for 5 min before release from a familiar site have enhanced ground homing speed compared with those placed in an opaque-sided box. It is assumed that previewing the surrounding landscape allows for faster homing since a bird denied this information must accumulate the knowledge on release. In experiment 1, using the same technique developed in these experiments but releasing the birds in pairs we showed that within familiar areas, homing pigeons can exploit a partner that has acquired more information, allowing them to home more quickly. In experiment 2 we attempted to test three potential strategies which may occur during homing flights. The results do not conclusively distinguish between these three mechanisms but suggest that orientation of the pairs of birds is most likely to have resulted from a compromise of individual tendencies, or from following the best homer, but not from following a ‘governing leader’. The consequence of these mechanisms is discussed.     

Antibacterial photodynamic therapy in dermatology.

Photodynamic therapy (PDT) appears to be endowed with several favourable features for the treatment of localized microbial infections, especially after the advent of cationic photosensitising agents (phenothiazines, meso-substituted porphyrins, polylysine-bound chlorins) which properly interact with the outer wall at the surface of several types of bacterial and yeast cells, increase their permeability, and allow significant amounts of photosensitizer to be accumulated at the level of the cytoplasmic membrane. These photosensitisers are characterized by a broad spectrum of activity, being effective toward both wild strain and antibiotic-resistant gram-positive and gram-negative bacteria and yeasts. In general, extensive eradication of pathogens can be achieved under mild irradiation conditions, such as short incubation times and low fluence-rates, which guarantees a high degree of selectivity in comparison with the main constituents of host tissues, such as keratinocytes and fibroblasts. Moreover, the photosensitised inactivation of microorganisms is typically a multi-target process; as a consequence, the selection of photoresistant microbial strains is very unlikely and has not been experimentally observed so far. Possible initial targets of antimicrobial PDT applications include periodontal diseases, impetigo, atopic dermatitis, acne vulgaris, infected wounds, and superinfected posriatic plaques.     

Neuromechanical strategies employed to increase jump height during the initiation of the squat jump.

The maximal height attained in a vertical jump is heavily influenced by the execution of a large countermovement prior to the upward motion. When a jump must be executed without a countermovement, as in a squat jump, the maximal jump height is reduced. During such conditions, the human body may use other strategies in order to increase performance. The purpose of this research was to investigate the effects of two strategies employed during the initiation of the squat jump: the premovement silent period (PSP), and the small amplitude countermovement (SACM). Fifteen elite male volleyball players (20.6 +/- 1.6 years) and 13 untrained males (20.2 +/- 1.7 years) performed 10 maximal effort squat jumps from identical starting positions. The electromyographic activity of the vastus lateralis and biceps femoris was measured in conjunction with the vertical ground reaction force and vertical displacement. It was found that the presence of a PSP or a SACM of 1-3 cm did not increase maximal squat jump height significantly (p > 0.05), in neither the highly trained athletes nor the untrained individuals. These results suggest that these strategies do not play a major role in the determination of jump height. Researchers have assumed that a squat jump is purely concentric, and that there are no facilitating mechanisms present that may influence the performance of the jump. This study provides evidence to support this assumption.     

Interaction of the PAS B domain with HSP90 accelerates hypoxia-inducible factor-1alpha stabilization.

Hypoxia-inducible factor (HIF) alpha subunits are induced under hypoxic conditions, when limited oxygen supply prevents prolyl hydroxylation-dependent binding of the ubiquitin ligase pVHL and subsequent proteasomal degradation. A short normoxic half-life of HIF-alpha and a very rapid hypoxic protein stabilization are crucial to the cellular adaptation to changing oxygen supply. However, the molecular requirements for the unusually rapid mechanisms of protein synthesis, folding and nuclear translocation are not well understood. We and others previously found that the chaperone heat-shock protein 90 (HSP90) can interact with HIF-1alpha in vitro. Here we show that HSP90 also interacts with HIF-2alpha and HIF-3alpha, suggesting a general involvement of HSP90 in HIF-alpha stabilization. The PAS B domain, common to all three alpha subunits, was required for HSP90 interaction. ARNT competed with HSP90 for binding to the PAS B domain since an excess of either component inhibited the activity of the other. HSP90 as well as the heterocomplex members HSP70 and p23, but not HSP40, were detected in immunoprecipitations of endogenous cellular HIF-1alpha. While HSP90 and HSP70 bound to HIF-1alpha predominantly under normoxic conditions, ARNT bound to HIF-1alpha primarily under hypoxic conditions, suggesting that ARNT displaced HSP90 from HIF-1alpha following nuclear translocation. Hypoxic accumulation of HIF-1alpha was delayed in a novel cell model deficient for HSP90beta as well as after treatment of wild-type cells with the HSP90 inhibitor geldanamycin, suggesting that HSP90 activity is involved in the rapid HIF-1alpha protein induction.