Fungal diversity in the Atacama Desert

Fungi are generally easily dispersed, able to colonise a wide variety of substrata and can tolerate diverse environmental conditions. However, despite these abilities, the diversity of fungi in the Atacama Desert is practically unknown. Most of the resident fungi in desert regions are ubiquitous. Some of them, however, seem to display specific adaptations that enable them to survive under the variety of extreme conditions of these regions, such as high temperature, low availability of water, osmotic stress, desiccation, low availability of nutrients, and exposure to high levels of UV radiation. For these reasons, fungal communities living in the Atacama Desert represent an unknown part of global fungal diversity and, consequently, may be source of new species that could be potential sources for new biotechnological products. In this review, we focus on the current knowledge of the diversity, ecology, adaptive strategies, and biotechnological potential of the fungi reported in the different ecosystems of the Atacama Desert.     

Sumoylation of AMPKβ2 subunit enhances AMP-activated protein kinase activity

AMP-activated protein kinase (AMPK) is a sensor of cellular energy status. It is a heterotrimer composed of a catalytic α and two regulatory subunits (β and γ). AMPK activity is regulated allosterically by AMP and by the phosphorylation of residue Thr-172 within the catalytic domain of the AMPKα subunit by upstream kinases. We present evidence that the AMPKβ2 subunit may be posttranslationally modified by sumoylation. This process is carried out by the E3-small ubiquitin-like modifier (SUMO) ligase protein inhibitor of activated STAT PIASy, which modifies the AMPKβ2 subunit by the attachment of SUMO2 but not SUMO1 moieties. Of interest, AMPKβ1 is not a substrate for this modification. We also demonstrate that sumoylation of AMPKβ2 enhances the activity of the trimeric α2β2γ1 AMPK complex. In addition, our results indicate that sumoylation is antagonist and competes with the ubiquitination of the AMPKβ2 subunit. This adds a new layer of complexity to the regulation of the activity of the AMPK complex, since conditions that promote ubiquitination result in inactivation, whereas those that promote sumoylation result in the activation of the AMPK complex.     

Disassortative mating, sexual specialization, and the evolution of gender dimorphism in heterodichogamous Acer opalus

In sexually polymorphic species, the morphs are maintained by frequency-dependent selection through disassortative mating. In heterodichogamous populations in which disassortative mating occurs between the protandrous and protogynous morphs, a decrease in female fitness in one morph is hypothesized to drive sexual specialization in the other morph, resulting in dimorphic populations. We test these ideas in a population of the heterodichogamous species, Acer opalus . We assessed both prospective gender of individuals in terms of their allocations and actual parentage using microsatellites; we found that most matings in A. opalus occur disassortatively. We demonstrate that the protogynous morph is maintained by frequency-dependent selection, but that maintenance of males versus protandrous individuals depends on their relative siring success, which changes yearly. Seeds produced later in the reproductive season were smaller than those produced earlier; this should compromise reproduction through ovules in protandrous individuals, rendering them male biased in gender. Time-dependent gender and paternity analyses indicate that the sexual morphs are specialized in their earlier sexual functions, mediated by the seasonal decrease in seed size. Our results confirm that mating patterns are context-dependent and change seasonally, suggesting that sexual specialization can be driven by seasonal effects on fitness gained through one of the two sexual functions.     

Retinoic acid binds to the C2-domain of protein kinase C(alpha)

Protein kinase C(alpha) (PKC(alpha)) is a key enzyme regulating the physiology of cells and their growth, differentiation, and apoptosis. PKC activity is known to be modulated by all-trans retinoic acid (atRA), although neither the action mechanism nor even the possible binding to PKCs has been established. Crystals of the C2-domain of PKC(alpha), a regulatory module in the protein that binds Ca(2+) and acidic phospholipids, have now been obtained by cocrystallization with atRA. The crystal structure, refined at 2.0 A resolution, shows that RA binds to the C2-domain in two locations coincident with the two binding sites previously reported for acidic phospholipids. The first binding site corresponds to the Ca(2+)-binding pocket, where Ca(2+) ions mediate the interactions of atRA with the protein, as they do with acidic phospholipids. The second binding site corresponds to the conserved lysine-rich cluster localized in beta-strands three and four. These observations are strongly supported by [(3)H]-atRA-binding experiments combined with site-directed mutagenesis. Wild-type C2-domain binds 2 mol of atRA per mol of protein, while the rate reduces to one in the case of C2-domain variants, in which mutations affect either Ca(2+) coordination or the integrity of the lysine-rich cluster site. Competition between atRA and acidic phospholipids to bind to PKC is a possible mechanism for modulating PKC(alpha) activity.     

Habitat attribute similarities reduce impacts of land‐use conversion on seed removal

Changes in land use strongly influence habitat attributes (e.g., herbaceous ground cover and tree richness) and can consequently affect ecological functions. Most studies have focused on the response of these ecological functions to land‐use changes within only a single vegetation type. These studies have often focused solely on agricultural conversion of forests, making it nearly impossible to draw general conclusions across other vegetation types or with other land‐use changes (e.g., afforestation). We examined the consequences of agricultural conversion for seed removal by ants in native grassland, savanna, and savanna‐forest habitats that had been transformed to planted pastures (Brachiaria decumbens) and tree plantations (Eucalyptus spp.) and explored if changes in seed removal were correlated with differences in habitat attributes between habitat types. We found that land‐use changes affected seed removal across the tree cover gradient and that the magnitude of impact was influenced by similarity in habitat attributes between native and converted habitats, being greater where there was afforestation (Eucalyptus spp in grassland and savanna). Herbaceous ground cover, soil hardness, and tree richness were the most important habitat attributes that correlated with differences in seed removal. Our results reveal that the magnitude of impact of land‐use changes on seed removal varies depending on native vegetation type and is associated with the type of habitat attribute change. Our findings have implications for biodiversity in tropical grassy systems: afforestation can have a greater detrimental impact on ecological function than tree loss.     

Diet composition of expanding breeding populations of the Magellanic Penguin

The Magellanic Penguin (Spheniscus magellanicus) is the most abundant and widely distributed seabird breeding on the Patagonian Coast of Argentina. We combined conventional stomach content and stable isotope analysis to assess Magellanic Penguin diet during the chick rearing stage at the two northernmost colonies in an area subject to fisheries. In 2011 and 2013, Thornfish (Bovichtus argentinus) was the main prey by mass at Complejo Islote Lobos (63.0% and 32.3%, respectively) and Argentine Anchovy (Engraulis anchoita) at Estancia San Lorenzo (85.2 and 63.3%, respectively). Magellanic Penguins from both colonies showed low isotopic niche overlap in 2011 (36%) and no overlap in 2013, suggesting a different use of prey species and/or foraging areas. Stable isotope mixing models showed that Argentine Anchovy (52.8%) and Thornfish (65.9%) were the main prey at Complejo Islote Lobos in 2011 and 2013, respectively, while Patagonian Redfish (Sebastes oculatus) (46.4%) and Squat Lobster (Munida gregaria) (50%) were the main prey at Estancia San Lorenzo in 2011 and 2013, respectively. Results show that in addition to Argentine Anchovy, previously recognized as main prey for breeding Magellanic Penguins in northern Patagonia, other juvenile or small sized fish are important diet items. Diet results suggest different scenarios of food conditions for each colony, despite the relative short distance between breeding locations. The low contribution of Argentine Hake (Merluccius hubbsi) and Argentine Shortfin Squid (Illex argentinus) suggests a low trophic overlap with commercial fisheries. The information provided is key to understand changes in the marine ecosystem and potential penguin-fishery interactions.     

Rapid development of a restored oyster reef facilitates habitat provision for estuarine fauna

Oyster reef restoration has become a principal strategy for ameliorating the loss of natural Crassostrea virginica populations and increasing habitat provision. In 2014, a large‐scale, high‐relief, 23‐ha subtidal C. virginica reef was restored at the historically productive Half Moon Reef in Matagorda Bay, TX, using concrete and limestone substrates. Encrusting and motile fauna were sampled seasonally until 17 months postrestoration at the restored reef and at adjacent unrestored sites. Restored oysters developed rapidly and were most abundant 3 months postrestoration, with subsequent declines possibly due to interacting effects of larval settlement success on new substrate versus post‐settlement mortality due to competitors and predators. Oyster densities were 2× higher than in a restored oyster population in Chesapeake Bay that was reported to be the largest reestablished metapopulation of native oysters in the world. Resident fauna on the restored reef were 62% more diverse, had 433% greater biomass, and comprised a distinct faunal community compared to unrestored sites. The presence of three‐dimensional habitat was the most important factor determining resident faunal community composition, indicating that substrate limitation is a major hindrance for oyster reef community success in Texas and other parts of the Gulf of Mexico. There were only minor differences in density, biomass, and diversity of associated fauna located adjacent (13 m) versus distant (150 m) to the restored reef. The two substrate types compared had little influence on oyster recruitment or faunal habitat provision. Results support the use of reef restoration as a productive means to rebuild habitat and facilitate faunal enhancement.     

Brain hypoxia and control of breathing: neuromechanical control

The effects of graded brain hypoxia on respiratory cycle timing, the lung inflation reflex, and respiratory compensation for an inspiratory flow-resistive load were studied in unanesthetized goats. Two models, inhalation and CO and acute reduction of brain blood flow (BBF) were used to produce comparable levels of brain hypoxia. The lung inflation reflex was assessed as the ratio of inspiratory time of an occluded breath to that of the preceding spontaneous breath (TIoccl/TIspont). Compensation for flow-resistive loading was assessed as the effect of the load upon the airway occlusion pressure response to rebreathing CO2 (delta P 0.1/delta PCO2). Major findings were 1) severe brain hypoxia (HbCO of 60% or BBF of 42%) caused tachypnea due to a 50% or more reduction of expiratory time but only a 20% or less reduction of inspiratory time; 2) moderate carboxyhemoglobinemia (HbCO of 25-30%) enhanced TIoccl/TIspont from 1.5 +/- 0.1 at control to 2.1 +/- 0.1, while severe brain hypoxia (HbCO of 60% and BBF of 42%) reduced the ratio to 1.0 +/- 0.2; and 3) compensation for a flow-resistive load, manifested by increases of delta P 0.1/delta PCO2 of 75-300% in the control state, was abolished at HbCO of 45-50% and BBF of 60%. The data suggest that in unanesthetized animals brain hypoxia elicits tachypnea largely by an effect on the expiratory phase of the bulbopontine timing mechanism. The observed enhancement of the lung inflation reflex and abolition of flow-resistive load compensation are best explained by hypoxic depression of higher than brain stem neural function.     

In vitro activity of minimised hammerhead ribozymes.

A number of minimised hammerhead ribozymes (minizymes) which lack stem II have been kinetically characterised. These minizymes display optimal cleavage activity at temperatures around 37 degrees C. The cleavage reactions of the minizymes are first order in hydroxide ion concentration up to around pH 9.3 above which the cleavage rate constants decline rapidly. The reactions show a biphasic dependence on magnesium-ion concentration; one of the interactions has an apparent dissociation constant of around 20 mM while the other appears to be very weak, showing no sign of saturation at 200 mM MgCl2. The minizymes are significantly less active than comparable, full-size ribozymes when cleaving short substrates. However, at a particular site in a transcribed TAT gene from HIV-1, minizymes are more effective than ribozymes.     

Celery transformation by Agrobacterium tumefaciens: cytological and genetic analysis of transgenic plants

Transgenic celery plants were obtained following co-cultivation of petiole explants with Agrobacterlum tumefaciens containing pMON200, a cointegrate vector carrying genes for kanamycin resistance and nopaline synthase. Transformants were selected by ability of callus to grow in the presence of 50mg/l kanamycin. Transformation was confirmed either by the presence of nopaline or by Southern blots. Cytological analysis of 14 transformed plants revealed chromosomal aberrations, both in structure and number. Only 20% of the regenerated plants had the normal karyotype. Kanamycin resistance behaved as a monogenic, dominant trait, segregating in a 3:1 ratio in three families derived from plants with normal karyotypes.Abbreviations KB Kilobases - 2-4D 2,4-diphenoxyacetic acid