Scale-dependent equilibrium in highly heterogeneous islands: plant geography of the northern Great Barrier Reef sand cays and shingle islets

In contrast to classical island biogeographical predictions, plant species richness is not monotonically related to island area or isolation for the northern Great Barrier Reef islands, and this cannot be accounted for as a ‘small island effect’. Many islands are composed of different terrain units bearing different floristic assemblages suggesting a modified‘terrain-floristic element’model for island biogeography. This requires definition of a time-scale for equilibrium considerations and emphasizes that equilibrium or first order perturbation (‘relaxation’) models may be inappropriate for some archipelagos.     

Determination of oral mucosal Poisson’s ratio and coefficient of friction from in-vivo contact pressure measurements

Despite their considerable importance to biomechanics, there are no existing methods available to directly measure apparent Poisson’s ratio and friction coefficient of oral mucosa. This study aimed to develop an inverse procedure to determine these two biomechanical parameters by utilizing in vivo experiment of contact pressure between partial denture and beneath mucosa through nonlinear finite element (FE) analysis and surrogate response surface (RS) modelling technique. First, the in vivo denture–mucosa contact pressure was measured by a tactile electronic sensing sheet. Second, a 3D FE model was constructed based on the patient CT images. Third, a range of apparent Poisson’s ratios and the coefficients of friction from literature was considered as the design variables in a series of FE runs for constructing a RS surrogate model. Finally, the discrepancy between computed in silico and measured in vivo results was minimized to identify the best matching Poisson’s ratio and coefficient of friction. The established non-invasive methodology was demonstrated effective to identify such biomechanical parameters of oral mucosa and can be potentially used for determining the biomaterial properties of other soft biological tissues.     

Scaling phloem transport: water potential equilibrium and osmoregulatory flow

In this work, the common assumption that phloem sap is in water potential equilibrium with the surrounding apoplast was examined. With a dimensionless model of phloem translocation that scales with just two dimensionless parameters (R?and F?), a ‘map’ of phloem behaviour as a function of these parameters was produced, which shows that the water potential equilibrium assumption (R?F? >> 1) is valid for essentially all realistic values of the relevant scales. When in water potential equilibrium, a further parameter reduction is possible that limits model dependence to a single parameter (F?), which describes the ratio of the solution's osmotic strength to its axial pressure drop. Due to the locally autonomous nature of individual sieve element/companion cell complexes, it is argued that long‐distance integrative control is most efficient when F? is large (that is, when the pressure drop is relatively small), permitting the sieve tube to regulate solute loading in response to global changes in turgor. This mode of transport has been called ‘osmoregulatory flow.’ Limitations on the pressure drop within the transport phloem could require that sieve tubes be shorter than the long axis of the plant, and thus arranged in series and hydraulically isolated from one another.     

'Locked-on' and 'locked-off' signal transduction mutations in the periplasmic domain of the Escherichia coli NarQ and NarX sensors affect nitrate- and nitrite-dependent regulation by NarL and NarP

The Escherichia coli NarX, NarQ, NarL and NarP proteins comprise a two-component regulatory system that controls the expression of many anaerobic electron-transport and fermentation-related genes in response to nitrate and nitrite. Either of the two sensor-transmitter proteins, NarX and NarQ, can activate the response-regulator proteins, NarL and NarP, which in turn are able to bind at their respective DNA regulatory sites to modulate gene expression. NarX contains a conserved 17 amino acid sequence, designated the ‘P-box’ element, that is essential for nitrate sensing. In this study we characterize narQ mutants that also confer altered nitrate control of NarL-dependent nitrate reductase (narGHJI ) and fumarate reductase (frdABCD) gene expression. While some narQ mutations cause the constitutive activation or repression of reporter-gene expression even when the cells are grown in the absence of the nitrate signal (i.e. a ‘locked-on’ phenotype), other mutations abolish nitrate-dependent control (i.e. a ‘locked-off’ phenotype). Interestingly the narQ (A42→T) and narQ (R50→Q) mutations along with the analogous narX18 (A46→T) and narX902 (R54→E) mutations also confer a ‘locked-on’ or a ‘locked-off’ phenotype in response to nitrite, the second environmental signal detected by NarQ and NarX. Furthermore, these narQ and narX mutations also affect NarP-dependent gene regulation of nitrite reductase (nrfABCDEFG) and aeg-46.5 gene expression in response to nitrite. We therefore propose that the NarQ sensor-transmitter protein also detects nitrate and nitrite in the periplasmic space via its periplasmic domain. A signal transduction model, which we previously proposed for NarX, is now extended to NarQ, in which a nitrate- or nitrite-detection event in the periplasmic region of the cell is followed by a signal transduction event through the inner membrane to the cytoplasmic domain of NarQ and NarX proteins to modulate their protein kinase/phosphatase activities.     

Peroxidase and Poly-Phenol Oxidase in Brassica juncea Plants Infected with Macrophomina phaseolina (Tassai) Goid. and their Implication in Disease Resistance

Studies on the peroxidase and poly-phenol oxidase activity in relatively resistant and susceptible strains of Brassica juncea at sequential intervals after inoculation with different isolates of Macrophomina phaseolina revealed that, fungus infected tissues had relatively higher activities of these oxidative enzymes in comparison to healthy plants, and tissues inoculated with ‘Weakly Virulent’ isolates always exhibited higher activity in comparison to ‘Moderately’, ‘Highly’ and ‘MostHighly Virulent’ isolates. At the early stages of the infection on 6th day, resistant plants showed higher activities in comparison to their susceptible counterparts. Very low activity of these enzymes could be recorded in healthy plants. Findings of this, study indicate the possible involvement of these oxidative enzymes in the resistance of this disease.     

Metallothionein concentration in the mussel Mytilus galloprovincialis as a biomarker of response to metal contamination: validation in the field

Mussels were translocated from a shell-fish breeding area (Sète, on the French Mediterranean coast) to sites exposed to trace element inputs in April 2000. They were recovered 3 months later. Whole soft tissues from all of the sites (n = 97) were analysed for arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc. Metallothioneins (MTs) were also measured in the digestive gland and in the remaining tissues (allowing calculation of whole soft tissue concentrations) at 22 of the 97 sites. MT concentrations in the digestive gland and the whole soft tissues were strongly correlated. The condition index varied with food availability at different sites. This did not influenced MT concentrations in the whole soft tissues, whereas the condition index was negatively correlated to trace element concentrations. A model is proposed to minimize this influence of condition. Metal concentrations adjusted using this model showed significant correlations with MT levels for those metals (cadmium, copper, nickel and zinc) that are known to bind to this protein, with the exception of mercury. Even in moderately contaminated sites, measurement of the MT level in the soft tissues of mussels was generally able to discriminate between different levels of contamination, allowing the use of a simplified procedure compared with dissection of the digestive gland. It is recommended to avoid translocation and sampling during the reproductive period, which is well documented for commercial species such as Mytilus sp.     

Differences in cold hardiness,carbohydrates, dehydrins and related gene expressions under an experimental deacclimation and reacclimation in Prunus persica

To boost our understanding of a recent outbreak of freezing injury, we sought to confirm distinctive features between the shoot tissues of the peach (Prunus persica) cultivars Daewol and Kiraranokiwami by mimicking unseasonable changes of temperatures that occur in the early spring through repeated deacclimation and reacclimation treatments. Patterns of cold hardiness declined dramatically during the deacclimation and rose during the reacclimation in both cultivars. Our results indicated that ‘Daewol’ possessed higher capacity in response to repeated deacclimation and reacclimation treatments than ‘Kiraranokiwami’. ‘Daewol’ showed more sensitive changes in the carbohydrates in response to warm and low temperatures compared with ‘Kiraranokiwami’. ‘Daewol’ indicated almost similar repeated down‐ and up‐patterns in soluble sugar content in response to repeated deacclimation and reacclimation, whereas it indicated repeated up‐ and down‐patterns in starch content. However, ‘Kiraranokiwami’ showed a progressive increase in the soluble sugar content and a progressive decrease in starch content. Notably, patterns of accumulation of a 60‐kDa dehydrin protein encoded by the PpDhn1 gene were confirmed through western blotting and paralleled fluctuations of cold hardiness in both cultivars. Expression of this dehydrin was weak in both cultivars during deacclimation but its band intensity increased during reacclimation. Changes in related genes (β‐amylase, PpDhn1, PpDhn2 and PpDhn3) were positively correlated with changes in cold hardiness throughout the experiment. Our results indicate that recent repeated warm periods may cause premature deacclimation in the early spring, and that more cold‐tolerant cultivar may be more resilient to freezing injury caused by unstable temperature conditions.     

‘Antlers inside’: are the skull structures of beaked whales (Cetacea: Ziphiidae) used for echoic imaging and visual display?

Skulls of many living and extinct beaked whales (Ziphiidae) contain various bizarre bone and tooth structures. Many of them show sexual dimorphism in their skull anatomy: males have bizarre skull structures, whereas females do not. Opinions differ as to what the function of these structures might be. Some believe that these are weapons; others, that they are sound transmitters. This article argues that these structures are the means of visual display. Many of the bizarre bone structures of beaked whales are not exposed like ‘visuals’ of terrestrial tetrapods, but are located deep in soft tissues. Nevertheless, toothed whales recognize objects (including three‐dimensional bodies), using echolocation. So, along with visual means, they can ‘see’ and ‘show’ their internal bone structures with echoic imaging and use them as informational sources in social interactions and in individual or species recognition. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 510–515.     

Function of the genetic element ‘Mona’ associated with fungicide resistance in Monilinia fructicola

The genetic element ‘Mona’ has been shown previously to be associated with resistance to demethylation inhibitors (DMIs) in Monilinia fructicola. In this study, the promoter activity of the ‘Mona’ element was demonstrated genetically and the activity was narrowed down to a 20‐bp active region through a series of deletions. ‘Mona’ knockout transformants (ΔMona) were generated from DMI‐resistant isolate Bmpc7, and EC₅₀ values and expression of the MfCYP51 gene were found to be reduced in transformants compared with the parental isolate. When the ‘Mona’ element was inserted into the upstream region of the MfCYP51 gene of the DMI‐sensitive isolate HG3, the EC₅₀ values and expression of the MfCYP51 gene increased in the transformants compared with the parental sensitive isolate. These results indicate that the ‘Mona’ element determines the DMI fungicide resistance through the up‐regulation of the expression of the downstream MfCYP51 gene. No fitness penalty was observed in knockout and insertion transformants, i.e. transformants showed similar mycelial growth rate, sporulation and ability to cause lesions on fruit compared with their parental isolates, suggesting that the ‘Mona’ element does not affect basal life activities.     

MRI-based experimentations of fingertip flat compression: Geometrical measurements and finite element inverse simulations to investigate material property parameters

Modeling human-object interactions is a necessary step in the ergonomic assessment of products. Fingertip finite element models can help investigating these interactions, if they are built based on realistic geometrical data and material properties. The aim of this study was to investigate the fingertip geometry and its mechanical response under compression, and to identify the parameters of a hyperelastic material property associated to the fingertip soft tissues.Fingertip compression tests in an MRI device were performed on 5 subjects at either 2 or 4 N and at 15° or 50°. The MRI images allowed to document both the internal and external fingertip dimensions and to build 5 subject-specific finite element models. Simulations reproducing the fingertip compression tests were run to obtain the material property parameters of the soft tissues.Results indicated that two ellipses in the sagittal and longitudinal plane could describe the external fingertip geometry. The internal geometries indicated an averaged maximal thickness of soft tissues of 6.4 ± 0.8 mm and a 4 ± 1 mm height for the phalanx bone. The averaged deflections under loading went from 1.8 ± 0.3 mm at 2 N, 50° to 3.1 ± 0.2 mm at 4 N, 15°. Finally, the following set of parameters for a second order hyperelastic law to model the fingertip soft tissues was proposed: C₀₁ = 0.59 ± 0.09 kPa and C₂₀ = 2.65 ± 0.88 kPa.These data should facilitate further efforts on fingertip finite element modeling.     

Vegetation and soil patterning in semi-arid mulga lands of Eastern Australia

Vegetation and soil patterns across a 200 ha semi-arid site 40 km north-west of Louth, NSW, are described using plant cover data from line transects and soils data from points, sampled systematically (50 m intervals) across the site. A patterned sequence of alternating groves and intergroves with three vegetation types was identified: an Eragrostis eriopoda savanna occurring on runoff slopes (<0.5%) from low ridges, with a Monachather paradoxa savanna occurring at the toe of these runoff slopes (intergroves), followed by an Acacia anuera woodland occurring on runon areas (groves, either as discrete islands or more continuous along drainage lines). Data on landform, micro-topography, and hydrological features indicate that the grove-intergrove pattern is maintained by differential erosion–deposition processes similar to the dynamic erosion–transfer–sink geomorphic systems described for Central Australia. This vegetation grove–intergrove patterning in Eastern Australia is similar to, but differs in detail from, such patterns reported for arid and semi-arid Western and Central Australia. Groves or ‘bands’ of A. anuera in the Centre and the West tend to occur on the downslope side of ‘risers’ or on ‘convex slope-breaks’ where in the East such groves occur in distinct 'steps’ or ‘flats’ in the landscape; there is a drop into the grove and a sharp ‘erosion-scarp’ below the grove. A prominent ‘grass band’, identified by cluster analysis as the M. paradoxa community type, occurs immediately upslope of A. anuera groves in the East. The A. anuera groves in the East are also fertile’ patches as soils data demonstrate that groves have much higher levels of organic and exchangeable nutrients (and plant cover) than soils in the intergroves. This paper demonstrates that patterning in mulga lands is more extensive geographically, and has a wider climatic range, than previously reported.     

Functional analysis of the uL11 protein impact on translational machinery

The ribosomal GTPase associated center constitutes the ribosomal area, which is the landing platform for translational GTPases and stimulates their hydrolytic activity. The ribosomal stalk represents a landmark structure in this center, and in eukaryotes is composed of uL11, uL10 and P1/P2 proteins. The modus operandi of the uL11 protein has not been exhaustively studied in vivo neither in prokaryotic nor in eukaryotic cells. Using a yeast model, we have brought functional insight into the translational apparatus deprived of uL11, filling the gap between structural and biochemical studies. We show that the uL11 is an important element in various aspects of ‘ribosomal life’. uL11 is involved in ‘birth’ (biogenesis and initiation), by taking part in Tif6 release and contributing to ribosomal subunit-joining at the initiation step of translation. uL11 is particularly engaged in the ‘active life’ of the ribosome, in elongation, being responsible for the interplay with eEF1A and fidelity of translation and contributing to a lesser extent to eEF2-dependent translocation. Our results define the uL11 protein as a critical GAC element universally involved in trGTPase ‘productive state’ stabilization, being primarily a part of the ribosomal element allosterically contributing to the fidelity of the decoding event.     

Artificial diets for rearing the coconut hispine beetle Brontispa longissima and its parasitoid Asecodes hispinarum

We tested artificial diets for rearing the coconut hispine beetle, Brontispa longissima, a serious invasive pest of coconut (Cocos nucifera) in Southeast Asia. We examined three artificial diets that were identical except for their agar content. The survival rate from hatching to adult emergence was 26.0% when beetles were reared on a ‘soft diet’ (20 g/l agar), 16.0% on a ‘hard diet’ (40 g/l agar), and 41.0% on a ‘mixed diet’, in which the hard diet was used for the first instar and the soft diet for later instars. Females raised as larvae on the mixed diet and then as adults on the soft diet laid few eggs, which did not hatch. However, females reared on the mixed diet as larvae and then on fresh leaves as adults consistently laid eggs that hatched. We then examined the suitability of B. longissima larvae reared on the mixed diet as hosts for the larval parasitoid Asecodes hispinarum, a specialist parasitoid of this beetle. Of the oviposited hosts, 75.0% became mummified and 41.7% produced adult wasps. These results indicate that the mixed diet may be useful for rearing B. longissima larvae as hosts for the rearing of A. hispinarum.     

The cannibalistic snail Agaronia propatula (Caenogastropoda,Mollusca) is reluctant to feed on autotomized ‘tails’ of conspecifics

Autotomy and cannibalism increase the complexity of the life history, population structure, and population dynamics of a species. Species in which autotomy is triggered by cannibalism have rarely been studied. It has been hypothesized that in the intertidal gastropod Agaronia propatula, autotomized tissues are highly attractive to cannibals and so increase the victim’s chance to escape. We tested the hypothesis by presenting autotomized ‘tails’ to foraging animals. The attack rates on autotomized ‘tails’ were lower than those on artificial objects reported previously. Autonomously moving autotomized ‘tails’ were more frequently ignored than non-moving and artificially moved ‘tail’ pieces. Thus, autotomized tissue repelled rather than attracted potential cannibals. Autotomy in A. propatula does not help to defend against cannibalism by offering the cannibal an attractive food item for consumption. It seems possible, though, that autotomized conspecifics are less attractive to cannibals than intact ones due to a repelling action of autotomized tissues.     

The life history and decline of the threatened Australian frog,Litoria raniformis

A popular idea amongst ecologists last century was that animals which exploit dynamic environments often display ‘fast’ life history strategies (high fecundity, rapid growth and maturation, and low or variable adult survival rates) relative to those which occupy more stable environments. Whilst the underlying theory has been discredited, the categorization remains of interest, because species with ‘fast’ life history traits are thought to be more robust to human‐induced environmental change than those with ‘slow’ life history traits. We examined the life history traits of the endangered Australian frog Litoria raniformis, to determine whether it displays ‘fast’ life history traits (like its sister species L. aurea and L. castanea), and to assess the role of these traits in the decline of this species. Mark‐recapture data confirmed that L. raniformis displays rapid growth and maturation. The data also suggest that L. raniformis displays relatively low adult survival rates. We propose that the ‘fast’ life history traits of this species are adaptive to metapopulation dynamics. In turn, we suggest that the rapid decline of L. raniformis may have resulted from metapopulation collapse, driven ultimately by habitat loss, degradation and fragmentation, and proximately by severe stochastic perturbations.     

The isolation of genes from the resurrection grass Sporobolus stapfianus which are induced during severe drought stress

A modification of the ‘cold plaque’ screening technique (Hodge et al., Plant Journal1992, 2, 257–260) was used to screen a cDNA library constructed from drought‐stressed leaf tissue of the desiccation tolerant (‘resurrection’) grass Sporobolus stapfianus. This technique allowed a large number of clones representing genes expressed at low abundance to be isolated. An examination of expression profiles revealed that several of these genes are induced in desiccation‐tolerant tissue experiencing severe drought stress. Further characterization indicated that the gene products encoded include an eIF1 protein translation initiation factor and a glycine‐ and proline‐rich protein which have not previously been associated with drought stress. In addition, genes encoding a serine/threonine phosphatase type 2C, a tonoplast‐intrinsic protein (TIP) and an early light‐inducible protein (ELIP) were isolated. A number of these genes are expressed differentially in desiccation‐tolerant and desiccation‐sensitive tissues, suggesting that they may be associated with the desiccation tolerance response of S. stapfianus. The results indicate that there may be unique gene regulation processes occurring during induction of desiccation tolerance in resurrection plants which allow different drought‐responsive genes to be selectively expressed at successive levels of water loss.