Characterization of recurrent somatic embryogenesis of alfalfa on auxin-free medium

Callus cultures from 300 genotypes of alfalfa (Medicago sativa L.) were initiated from leaf, petiole, and internode explants placed on Blaydes medium containing 10.74 M -naphthaleneacetic acid, 11.42 M indole-3-acetic acid, and 9.29 M kinetin. Five genotypes produced somatic embryos. Upon transfer of these embryos to growth regulator-free Murashige and Skoog medium with B₅ vitamins, new somatic embryos repeatedly formed directly on older somatic embryos without an intervening callus phase in a cycle lasting about 30 days. These cultures have been maintained for two years, during which time their embryogenic capacity has remained stable. New embryogenic cultures could be started repeatedly from these genotypes. The elimination of sugars from the medium could stop recurrent embryogenesis. Glucose, maltose, and fructose stimulated recurrent embryogenesis more effectively than sucrose. Sucrose was superior to lactose, while sorbitol and mannitol did not stimulate recurrent somatic embryogenesis. The absence of nicotinic acid in the medium, as long as sucrose was present, was lethal to embryos of three of the five tested genotypes. The ability of this system to propagate embryos exponentially offers potential for development of new gene transfer systems and application to artificial seed technology.Abbreviations NAA -naphthaleneacetic acid - RSE recurrent somatic embryogenesis     

Polarized secretion of IGF-I and IGF-I binding protein activity by cultured aortic endothelial cells

Insulin-like growth factor-I (IGF-I) secretion by the vascular endothelium has been proposed to play a role in the regulation of vascular smooth muscle cell proliferation. Because vascular smooth muscle cells are adjacent to the abluminal surface of the endothelium, we tested the hypothesis that secretion of IGF-I by endothelial cells is polarized. Porcine aortic endothelial cells were cultured on permeable membranes and IGF-I measured by radioimmunoassay. Basal secretion exceeded apical secretion by a ratio of 2.3 ± 0.2:1.0 (P < 0.05). We also identified 35 kDa IGF-I binding protein activity that is preferentially secreted on the basal surface of endothelial cells. We conclude that both IGF-I and IGF-I binding protein activity secretion by endothelial cells is polarized towards the basal surface of the endothelium. A polarized secretion mechanism for IGF-I may be of importance in the normal growth and differentiation of the vasculature as well as in the development of vascular pathology. © 1993 Wiley-Liss, Inc.     

Clearance of Exogenous Dopamine in Rat Dorsal Striatum and Nucleus Accumbens: Role of Metabolism and Effects of Locally Applied Uptake Inhibitors

In vivo electrochemistry was used to investigate the mechanisms contributing to the clearance of locally applied dopamine in the dorsal striatum and nucleus accumbens of urethane-anesthetized rats. Chronoamperometric recordings were continuously made at 5 Hz using Nafion-coated carbon fiber electrodes. When a finite amount of dopamine was pressure-ejected at 5-min intervals from a micropipette adjacent to the electrode, transient and reproducible dopamine signals were detected. Substitution of L-a-methyldopamine, a substrate for the dopamine transporter but not for monoamine oxidase, for dopamine in the micropipette did not substantially alter the time course of the resulting signals. This indicates that metabolism of locally applied dopamine to 3,4-dihydroxyphenylacetic acid is not responsible for the decline in the dopamine signal. Similarly, changing the applied oxidation potential from ±0.45 to ±0.80 V, which allows for detection of 3-methoxytyramine formed from dopamine via catechol-O-methyltransferase, had little effect on signal amplitude or time course. In contrast, lesioning the dopamine terminals with 6-hydroxydopamine, or locally applying the dopamine uptake inhibitors cocaine or nomifensine before pressure ejection of dopamine, significantly increased the amplitude and time course of the dopamine signals in both regions. The effects of cocaine and nomifensine were greater in the nucleus accumbens than in the dorsal striatum. Local application of lidocaine and procaine had no effect on the dopamine signals. Initial attempts at modeling resulted in curves that were in qualitative agreement with our experimental findings. Taken together, these data indicate that (1) uptake of dopamine by the neuronal dopamine transporter, rather than metabolism or diffusion, is the major mechanism for clearing locally applied dopamine from the extracellular milieu of the dorsal striatum and nucleus accumbens, and (2) the nucleus accumbens is more sensitive to the effects of inhibitors of dopamine uptake than is the dorsal striatum.     

Crystal structure,conformational analysis,and molecular dynamics of tetra-O-methyl-(+) -catechin

The structure of tetra-O-methyl- (+) -catechin has been determined in the crystalline state. Two independent molecules, denoted structure A and structure B, exist in the unit cell. Crystals are triclinic, space group P1, a = 4.8125(2) Å, b = 12.9148(8) Å, c = 13.8862(11) Å, α = 86.962(6) °, β = 89.120(5)°, γ = 88.044(5)°, Z = 2, D_c = 1.336 g cm^?3, R = 0.033 for 6830 observations. The heterocyclic rings of the crystal structures are compared to previous results for 8-bromotetra-O-methyl-(+)-catechin, penta-O-acetyl-(+)-catechin, and (?) -epicatechin. One of the two molecules has a heterocyclic ring conformation similar to that observed previously for (?)-epicatechin, and the other has a heterocyclic ring conformation similar to one predicted earlier in a theoretical analysis of dimers of (+)-catechin and (?) -epicatechin. Both structure A and structure B in the crystal have heterocyclic ring conformations that place the dimethoxyphenyl substituent at C(2) in the equatorial position. However, this heterocyclic ring conformation does not explain the proton nmr coupling constant measured in solution. Molecular dynamics simulations show an equatorial ? axial interconversion of the heterocyclic ring, which can explain the nmr results. © 1993 John Wiley & Sons, Inc.     

H assignment and secondary structure determination of human melanoma growth stimulating activity (MGSA) by NMR spectroscopy

The solution structure of melanoma growth stimulating activity (MGSA) has been investigated using proton NMR spectroscopy. Sequential resonance assignments have been carried out, and elements of secondary structure have been identified on the basis of NOE, coupling constant, chemical shift, and amide proton exchange data. Long-range NOEs have established that MGSA is a dimer in solution. The secondary structure and dimer interface of MGSA appear to be similar to those found previously for the homologous chemokine interleukin-8 [Clore et al. (1990) Biochemistry 29, 1689-1696]. The MGSA monomer contains a three stranded anti-parallel β-sheet arranged in a ‘Greek-key’ conformation, and a C-terininal -helix (residues 58 69).     

A deterministic analysis of self-incompatibility alleles

A number of plant species have a self-incompatibility locus that prevents self-fertilization. We 'analyse a deterministic model with an arbitrary number of alleles. We prove that the only polymorphic equilibrium is the one for which all (heterozygous) genotypes are equally frequent, and we prove that all (initially) polymorphic populations converge to this equilibrium.     

Identifying historical and future global change drivers that place species recovery at risk

Ecosystem management in the face of global change requires understanding how co-occurring threats affect species and communities. Such an understanding allows for effective management strategies to be identified and implemented. An important component of this is differentiating between factors that are within (e.g. invasive predators) or outside (e.g. drought, large wildfires) of a local manager's control. In the global biodiversity hotspot of south-western Australia, small- and medium-sized mammal species are severely affected by anthropogenic threats and environmental disturbances, including invasive predators, fire, and declining rainfall. However, the relative importance of different drivers has not been quantified. We used data from a long-term monitoring program to fit Bayesian state-space models that estimated spatial and temporal changes in the relative abundance of four threatened mammal species: the woylie (Bettongia penicillata), chuditch (Dasyurus geoffroii), koomal (Trichosurus vulpecula) and quenda (Isoodon fusciventor). We then use Bayesian structural equation modelling to identify the direct and indirect drivers of population changes, and scenario analysis to forecast population responses to future environmental change. We found that habitat loss or conversion and reduced primary productivity (caused by rainfall declines) had greater effects on species' spatial and temporal population change than the range of fire and invasive predator (the red fox Vulpes vulpes) management actions observed in the study area. Scenario analysis revealed that a greater extent of severe fire and further rainfall declines predicted under climate change, operating in concert are likely to further reduce the abundance of these species, but may be mitigated partially by invasive predator control. Considering both historical and future drivers of population change is necessary to identify the factors that risk species recovery. Given that both anthropogenic pressures and environmental disturbances can undermine conservation efforts, managers must consider how the relative benefit of conservation actions will be shaped by ongoing global change.     

Change in climatically suitable breeding distributions reduces hybridization potential between Vermivora warblers

Aim

Climate change is affecting the distribution of species and subsequent biotic interactions, including hybridization potential. The imperiled Golden-winged Warbler (GWWA) competes and hybridizes with the Blue-winged Warbler (BWWA), which may threaten the persistence of GWWA due to introgression. We examined how climate change is likely to alter the breeding distributions and potential for hybridization between GWWA and BWWA.

Location

North America.

Methods

We used GWWA and BWWA occurrence data to model climatically suitable conditions under historical and future climate scenarios. Models were parameterized with 13 bioclimatic variables and 3 topographic variables. Using ensemble modeling, we estimated historical and modern distributions, as well as a projected distribution under six future climate scenarios. We quantified breeding distribution area, the position of and amount of overlap between GWWA and BWWA distributions under each climate scenario. We summarized the top explanatory variables in our model to predict environmental parameters of the distributions under future climate scenarios relative to historical climate.

Results

GWWA and BWWA distributions are projected to substantially change under future climate scenarios. GWWA are projected to undergo the greatest change; the area of climatically suitable breeding season conditions is expected to shift north to northwest; and range contraction is predicted in five out of six future climate scenarios. Climatically suitable conditions for BWWA decreased in four of the six future climate scenarios, while the distribution is projected to shift east. A reduction in overlapping distributions for GWWA and BWWA is projected under all six future climate scenarios.

Main Conclusions

Climate change is expected to substantially alter the area of climatically suitable conditions for GWWA and BWWA, with the southern portion of the current breeding ranges likely to become climatically unsuitable. However, interactions between BWWA and GWWA are expected to decline with the decrease in overlapping habitat, which may reduce the risk of genetic introgression.     

The direction of mothers' and daughters' preferences and the heritability of male ornaments in red jungle fowl (Gallus gallus)

We used a breeding design involving 18 sires and 108 dams tostudy the heritabilities of male ornaments in red jungle fowl(Gallus gallus). Ornaments used by females to choose mates showedlow heritabilities, with the exception of comb and wattle measures.The general absence of heritability suggests that a geneticcovariance did not exist at the time of this study between mostmale ornaments and female preferences for those ornaments. Thisresult is contrary to a key prediction of the arbitrary or Fisherianhypothesis of sexual selection. Comb size and color are condition-dependenttraits that reflect short-term changes in health, and comb sizeof males was positively correlated with offspring weight. Ourresults are consistent with the expectation of good-genes hypothesesthat male ornaments reflect the ability of males to withstandenvironmental stresses.     

Two centuries of spatial and temporal dynamics of freshwater fish introductions

Aim

Investigating major freshwater fish flows (translocations) between biogeographic regions and their temporal dynamics and also quantifying spatial patterns and temporal changes in the array of introduced species, and the emergence and distance between major donor and recipient regions.

Location

Global.

Time Period

1800–2020.

Major Taxa Studied

Freshwater fishes.

Methods

We analysed a global dataset on freshwater fish introductions (4241 events of 688 species). Freshwater fish flows were investigated with flow diagrams and χ² tests, while PERMANOVA (permutational multivariate analysis of variance) was used to test the association between species and regions and temporal shifts. Cluster analysis revealed major recipient areas and composition of the introduced species. Finally, changes in distances between donor and recipient sites were tested with PERMANOVA.

Results

The number of introductions between biogeographic regions mirrored the European and North American dominance before World War II (WWII) and the trends in recreational fishing, biocontrol programmes and food production, especially in the Sino-Oriental region, which has a long tradition of aquaculture and fishkeeping. Over the years, the origins and composition of introduced species changed uniquely in each biogeographic region, although the most introduced species are common to every region. Salmonids and other cold-water species were frequently introduced before the 1950s, whereas tropical ornamental and aquaculture species currently prevail. Distances between donor and recipient sites did not vary over the time. After WWII, the Sino-Oriental region consolidated its dominance and the Ethiopian and Neotropical regions emerged as new global donor and recipient regions.

Main Conclusions

Global policy should focus on tropical ornamental and aquaculture species, which could benefit from global warming, especially in the Sino-Oriental region, because it currently dominates freshwater fish species flows, and the Ethiopian and Neotropical regions, because they recently emerged as important global donor and recipient regions of freshwater fish introductions.