Environment and position of first bud to break on apple shoots affects lateral outgrowth

A study was conducted to determine which bud (terminal or lateral) breaks first, and thereby exerts primigenic dominance, on ‘Granny Smith’ and ‘Golden Delicious’, 1-year-old apple (Malus × domestica Borkh.) shoots grown in two locations in the Western Cape, South Africa, with differing degrees of chilling. Primigenic dominance of laterals was more common in a warm area than a cool area, and more common in ‘Granny Smith’ than ‘Golden Delicious’. Laterals rarely broke before the terminal in ‘Golden Delicious’, and so differences in lateral development due to position of first bud to break were only analyzed in ‘Granny Smith’ shoots from this point on in the study. In ‘Granny Smith’, lateral budbreak and growth was influenced by the position of the first bud to break on the shoot, but did not differ between locations. On ‘Granny Smith’ shoots with primigenic dominance of the terminal, lateral budbreak and growth was suppressed, in accordance with the typical ‘delayed foliation’ commonly observed in warm winter climates. However, when at least one lateral broke before the terminal, lateral budbreak and growth were similar to previous observations in cold winter areas.     

Life on high: the diversity of small mammals at high altitude in South Africa

The Great Escarpment is the major mountain system in South Africa, yet very few biological surveys have been conducted outside of the well-known Drakensberg section. This is surprising given the important role that mountains play in local and global biodiversity patterns. In this study, small mammal diversity and community composition were estimated at three high altitude (>1,700?m) sites within the Sneeuberg Mountain Complex (SMC) of the Great Escarpment, South Africa from June 2009 to May 2010. The influences of selected environmental variables on diversity were also tested. Of 423 live-captures, a total of 292 unique individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were identified during 5,280 trap nights. No single environmental variable could account for the variation observed in diversity measurements but vegetation height appeared to be the most important factor to influence the number of individuals captured. It is hypothesised that the high species richness and diversity of small mammals observed in the SMC compared to other parts of the Great Escarpment is due to the SMC being located in a transition zone of the Grassland and Nama-Karoo biomes. Our results suggest that the SMC could be important in conserving small mammal species from western and eastern assemblages across South Africa.     

Ultrafast Red Light Activation of Synechocystis Phytochrome Cph1 Triggers Major Structural Change to Form the Pfr Signalling-Competent State

Phytochromes are dimeric photoreceptors that regulate a range of responses in plants and microorganisms through interconversion of red light-absorbing (Pr) and far-red light-absorbing (Pfr) states. Photoconversion between these states is initiated by light-driven isomerization of a bilin cofactor, which triggers protein structural change. The extent of this change, and how light-driven structural changes in the N-terminal photosensory region are transmitted to the C-terminal regulatory domain to initiate the signalling cascade, is unknown. We have used pulsed electron-electron double resonance (PELDOR) spectroscopy to identify multiple structural transitions in a phytochrome from Synechocystis sp. PCC6803 (Cph1) by measuring distances between nitroxide labels introduced into the protein. We show that monomers in the Cph1 dimer are aligned in a parallel ‘head-to-head’ arrangement and that photoconversion between the Pr and Pfr forms involves conformational change in both the N- and C-terminal domains of the protein. Cryo-trapping and kinetic measurements were used to probe the extent and temporal properties of protein motions for individual steps during photoconversion of Cph1. Formation of the primary photoproduct Lumi-R is not affected by changes in solvent viscosity and dielectric constant. Lumi-R formation occurs at cryogenic temperatures, consistent with their being no major structural reorganization of Cph1 during primary photoproduct formation. All remaining steps in the formation of the Pfr state are affected by solvent viscosity and dielectric constant and occur only at elevated temperatures, implying involvement of a series of long-range solvent-coupled conformational changes in Cph1. We show that signalling is achieved through ultrafast photoisomerization where localized structural change in the GAF domain is transmitted and amplified to cause larger-scale and slower conformational change in the PHY and histidine kinase domains. This hierarchy of timescales and extent of structural change orientates the histidine kinase domain to elicit the desired light-activated biological response.     

Algal metallothioneins: secondary metabolites and proteins

Metallothioneins, MT's, are low-molecular-weight, cysteine-rich, polypeptides that complex ‘soft’ metal ions in thiol clusters. They are structurally diverse. Some MT's are gene products, while others are secondary metabolites. Two of the three classes of MT have been identified in algae. Eukaryotic algae possess the secondary metabolites referred to as class III MT. There is no unequivocal evidence that MT genes occur in eukaryotic algae. However, the products of MT genes have been identified in cyanobacteria. These genes and their metal regulatory elements remain to be isolated and characterized. MT's have attracted interest from researchers involved in a wide range of disciplines including bioinorganic chemistry, biochemistry, molecular biology, physiology, toxicology, environmental science and medicine. Although, the precise physiological roles of these polypeptides remain undefined, a large number of functions have been speculated. These molecules chelate toxic trace metals, such as Cd, thereby reducing the concentration of cytotoxic, free-metal ions. Furthermore, some MT's are believed to be involved in zinc and copper homoeostasis. Future studies should reveal whether or not some of the diversity of MT structure reflects a diversity of function.     

A new take on prions: preventing Alzheimer's disease

Alzheimer's disease is a major neurodegenerative disease of the brain, the incidence of which increases dramatically in old age. Currently, no drugs are available to halt or slow the progression of this disease, which poses an ever-expanding burden on health services, families and society. The prion protein has become infamous owing to its role as the causative agent of the transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease in humans. However, our view of the prion protein as an unwanted, harmful entity has been challenged recently. New data indicate that the normal cellular form of the prion protein might have a crucial role in suppressing the production of the amyloid-beta peptide, the neurotoxic molecule involved in the pathogenesis of Alzheimer's disease.     

Three novel pigmentation mutants generated by genome-wide random ENU mutagenesis in the mouse

Three mutant mice with pigmentation phenotypes were recovered from a genomewide random mouse chemical mutagenesis study. White toes (Whto; MGI:1861986), Belly spot and white toes (Bswt; MGI:2152776) and Dark footpads 2 (Dfp2; MGI:1861991) were identified following visual inspection of progeny from a male exposed to the point mutagen ethylnitrosourea (ENU). In order to rapidly localize the causative mutations, genome-wide linkage scans were performed on pooled DNA samples from backcross animals for each mutant line. Whto was mapped to proximal mouse chromosome (Mmu) 7 between Cen (the centromere) and D7Mit112 (8.0 cM from the centromere), Bswt was mapped to centric Mmul between D1Mit214 (32.1 cM) and D1Mit480 (32.8 cM) and Dfp2 was mapped to proximalMmu4 between Cen and D4Mit18 (5.2 cM). Whto, Bswt and Dfp2 may provide novel starting points in furthering the elucidation of genetic and biochemical pathways relevant to pigmentation and associated biological processes.     

Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna

We measured stem CO2 efflux and leaf gas exchange in a tropical savanna ecosystem in northern Australia, and assessed the impact of fire on these processes. Gas exchange of mature leaves that flushed after a fire showed only slight differences from that of mature leaves on unburned trees. Expanding leaves typically showed net losses of CO2 to the atmosphere in both burned and unburned trees, even under saturating irradiance. Fire caused stem CO2 efflux to decline in overstory trees, when measured 8 weeks post-fire. This decline was thought to have resulted from reduced availability of C substrate for respiration, due to reduced canopy photosynthesis caused by leaf scorching, and to priority allocation of fixed C towards reconstruction of a new canopy. At the ecosystem scale, we estimated the annual above-ground woody-tissue CO2 efflux to be 275 g C m(-2) ground area year(-1) in a non-fire year, or approximately 13% of the annual gross primary production. We contrasted the canopy physiology of two co-dominant overstory tree species, one of which has a smooth bark on its branches capable of photosynthetic re-fixation (Eucalyptus miniata), and the other of which has a thick, rough bark incapable of re-fixation (Eucalyptus tetrodonta). Eucalyptus miniata supported a larger branch sapwood cross-sectional area in the crown per unit subtending leaf area, and had higher leaf stomatal conductance and photosynthesis than E. tetrodonta. Re-fixation by photosynthetic bark reduces the C cost of delivering water to evaporative sites in leaves, because it reduces the net C cost of constructing and maintaining sapwood. We suggest that re-fixation allowed leaves of E. miniata to photosynthesize at higher rates than those of E. tetrodonta, while the two invested similar amounts of C in the maintenance of branch sapwood.     

Australia's Dengue Risk Driven by Human Adaptation to Climate Change

Background

The reduced rainfall in southeast Australia has placed this region''s urban and rural communities on escalating water restrictions, with anthropogenic climate change forecasts suggesting that this drying trend will continue. To mitigate the stress this may place on domestic water supply, governments have encouraged the installation of large domestic water tanks in towns and cities throughout this region. These prospective stable mosquito larval sites create the possibility of the reintroduction of Ae. aegypti from Queensland, where it remains endemic, back into New South Wales and other populated centres in Australia, along with the associated emerging and re-emerging dengue risk if the virus was to be introduced.

Methodology/Principal Findings

Having collated the known distribution of Ae. aegypti in Australia, we built distributional models using a genetic algorithm to project Ae. aegypti''s distribution under today''s climate and under climate change scenarios for 2030 and 2050 and compared the outputs to published theoretical temperature limits. Incongruence identified between the models and theoretical temperature limits highlighted the difficulty of using point occurrence data to study a species whose distribution is mediated more by human activity than by climate. Synthesis of this data with dengue transmission climate limits in Australia derived from historical dengue epidemics suggested that a proliferation of domestic water storage tanks in Australia could result in another range expansion of Ae. aegypti which would present a risk of dengue transmission in most major cities during their warm summer months.

Conclusions/Significance

In the debate of the role climate change will play in the future range of dengue in Australia, we conclude that the increased risk of an Ae. aegypti range expansion in Australia would be due not directly to climate change but rather to human adaptation to the current and forecasted regional drying through the installation of large domestic water storing containers. The expansion of this efficient dengue vector presents both an emerging and re-emerging disease risk to Australia. Therefore, if the installation and maintenance of domestic water storage tanks is not tightly controlled, Ae. aegypti could expand its range again and cohabit with the majority of Australia''s population, presenting a high potential dengue transmission risk during our warm summers.