Genomic instability in mice lacking histone H2AX

Higher order chromatin structure presents a barrier to the recognition and repair of DNA damage. Double-strand breaks (DSBs) induce histone H2AX phosphorylation, which is associated with the recruitment of repair factors to damaged DNA. To help clarify the physiological role of H2AX, we targeted H2AX in mice. Although H2AX is not essential for irradiation-induced cell-cycle checkpoints, H2AX-/- mice were radiation sensitive, growth retarded, and immune deficient, and mutant males were infertile. These pleiotropic phenotypes were associated with chromosomal instability, repair defects, and impaired recruitment of Nbs1, 53bp1, and Brca1, but not Rad51, to irradiation-induced foci. Thus, H2AX is critical for facilitating the assembly of specific DNA-repair complexes on damaged DNA.     

Nutrient uptake by intact mycorrhizal Pinus sylvestris seedlings: a diagnostic tool to detect copper toxicity

We developed a nondestructive method for detecting early toxic effects of inflethal copper (Cu) concentrations on ectomycorrhizal and non-mycorrhizal (NM) Scots pine (Pinus sylvestris L.) seedlings. The fungal symbionts examined were Paxillus involutus (Fr.) Fr., Suillus luteus (Fr.) S.F. Gray and Thelephora terrestris (Ehrh.) Fr. The accumulation of Cu in needles and fungal development (ergosterol) in roots and infstrate were assessed. Inorganic phosphate (P(i)) and ammonium (NH(4) (+)) uptake capacities were determined in a semi-hydroponic cultivation system on intact P-limited plants that were exposed for 3 weeks to 0.32 (control), 8 or 16 &mgr;moles Cu(2+). Short-term effects of a 1-hour exposure to 32 &mgr;moles Cu(2+) on nutrient uptake rates were also determined. None of the Cu(2+) treatments affected plant growth or root ergosterol concentrations. The active fungal biomass in infstrate invaded by S. luteus was reduced by 50% in the 16 &mgr;M Cu(2+) treatment compared with the control treatment; however, colonization by S. luteus prevented an increased accumulation of Cu in the needles. In contrast, the 16 &mgr;M Cu(2+) treatment caused a 2.2-fold increase in needle Cu concentration in NM plants. Ergosterol concentrations in the infstrate colonized by P. involutus and T. terrestris were not affected by 16 &mgr;molar Cu(2+). Although P. involutus and T. terrestris were less sensitive to Cu(2+) than S. luteus, T. terrestris did not prevent the accumulation of Cu in needles of its host plant in the 16 &mgr;molar Cu(2+) treatment. Mycorrhizal plants consistently had higher P(i) and NH(4) (+) uptake capacities than NM plants. In the control treatment, specific P(i) uptake rates were almost 10, 4 and 3 times higher in plants associated with P. involutus, S. luteus and T. terrestris, respectively, than in NM plants, and specific NH(4) (+) uptake rates were about 2, 2 and 5 times higher, respectively, than those of NM seedlings. Compared with the corresponding control plants, a 3-week exposure to 8 &mgr;M Cu(2+) had no effect on the nutrient uptake potential of plants. In contrast, the 16 &mgr;M Cu(2+) treatment significantly reduced P(i) uptake capacity of all plants and decreased NH(4) (+) uptake capacity of seedlings colonized by S. luteus or T. terrestris. The 32 &mgr;M Cu(2+) 1-h shock treatment reduced specific NH(4) (+) and P(i) uptake rates of roots colonized by S. luteus to 39 and 77%, respectively, of the original rates. The Cu(2+) 1-h shock treatment reduced the NH(4) (+) uptake rate of NM plants by 51%.     

Spiromesifen toxicity to the spider mite <Emphasis Type="Italic">Tetranychus urticae</Emphasis> and selectivity to the predator <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>

Tetranychus urticae Koch (Acari: Tetranychidae) is a major pest of several agricultural crops and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is an important natural enemy of this pest mite. The objective of the study was to evaluate the effect of spiromesifen on the development and reproduction of T. urticae, and to assess the influence of spiromesifen and other acaricides on the population growth rates of the spider mite and its predator, N. californicus. Toxicity tests with spiromesifen at different life stages of T. urticae indicated that eggs less than 72 h old were more sensitive than other development stages. The oviposition rate of T. urticae was significantly affected by spiromesifen. Experiments on the effects of spiromesifen on the growth rates of T. urticae and N. californicus indicated that spiromesifen is innocuous to the predaceous mite but highly toxic to the spider mite, leading to population suppression in 10 days. Fenpropathrin, acephate and neem oil were not harmful to N. californicus, but were not so efficient as spiromesifen in controlling T. urticae, and had significantly less influence on the population growth rates of the spider mite. Among these three products, only neem oil caused significant reduction in the growth rate of T. urticae. Chlorfenapyr, abamectin, milbemectin and diafenthiuron significantly affected the population growth rates of T. urticae and N. californicus. Spiromesifen was the most promising acaricide for managing the two-spotted spider mite, when used in combination with N. californicus.     

Biochemical and anatomical features of adventitious rhizogenesis in apical and basal mini-cuttings of Ilex paraguariensis

New Forests - In order to better understand the physiological and technical aspects of yerba mate vegetative propagation, the present study sought to evaluate the rhizogenic capacity of apical and...     

Rescue of cardiac defects in id knockout embryos by injection of embryonic stem cells

We report that Id knockout mouse embryos display multiple cardiac defects, but mid-gestation lethality is rescued by the injection of 15 wild-type embryonic stem (ES) cells into mutant blastocysts. Myocardial markers altered in Id mutant cells are restored to normal throughout the chimeric myocardium. Intraperitoneal injection of ES cells into female mice before conception also partially rescues the cardiac phenotype with no incorporation of ES cells. Insulin-like growth factor 1, a long-range secreted factor, in combination with WNT5a, a locally secreted factor, likely account for complete reversion of the cardiac phenotype. Thus, ES cells have the potential to reverse congenital defects through Id-dependent local and long-range effects in a mammalian embryo.     

How good are tropical forest patches for ecosystem services provisioning?

Native forests play an important role regarding ecosystem services related to biodiversity, water, and nutrient cycling, and the intensity of those services should be related to the amount, configuration and quality of the forest. However, in highly dynamic landscapes, such as some tropical regions, ecosystem services are potentially affected not only by the present landscape structure, but also by the historical land use. Here we propose a simple methodological framework to evaluate the contribution of past landscape dynamics and present landscape structure in the provision of ecosystem services. We applied this framework to a traditional agricultural landscape from the Brazilian Atlantic Forest hotspot, where natural forests cover has increased from 8 to 16 % in the last 60 years (1962–2008), and where old forests are being reduced while young forests are being regenerated. Forests of different ages, in association with current landscape structure, reveal a mosaic of forest patches under different conditions, implying different abilities to deliver ecosystem services. With the replacement of old-growth forests by young-regenerating forests and a high level of forest fragmentation, less than 1/4 of the current forest cover is able to fully satisfy the ecosystem service demands. To avoid such tendency, government policies should not only focus on increasing forest cover, but also in conserving old-growth forest fragments or increasing forest quality. The proposed methodology allows integrating historical land use and current landscape structure to evaluate ecosystem services provision and can be useful to establish programs of payment for ecosystem services.     

Application of stressed and microencapsulated Meyerozyma caribbica for the control of Colletotrichum gloeosporioides in avocado (Persea americana Mill. cv. Hass)

Journal of Plant Diseases and Protection - The antagonistic capacity of Meyerozyma caribbica subjected to hydric and thermal stress and microencapsulated by spray drying against Colletotrichum...     

Selected carbon fluxes in Pinus ponderosa-based silvopastoral systems, exotic plantations and natural pastures on volcanic soils in the Chilean Patagonia

This study was undertaken to measure certain carbon (C) fluxes in a Pinus ponderosa-based silvopastoral systems (SPS) in Patagonia, Chile. Results are compared to those from adjacent 18-year-old managed pine plantations (PPP) and natural prairie (PST). Litter decomposition was determined using the litterbag method. Leached soil solution was collected with tension lysimeters at 80 cm depth, and soil respiration evaluated in situ with the soda lime technique. Wind direction influenced the litterfall distribution in SPS, with 94 % falling in the tree strips and within 3 m on the east side. In the first 6 months the initial needle decomposition was low and less than 5 % of the initial mass. The overall soil organic carbon (SOC) and N contents (0–40 cm depth) decreased significantly in the order SPS > PST > PPP, and within SPS were greater in the alleys, starting at 2.5 m from the tree strip, with the highest values always eastward of the strip, suggesting influence by the wind direction. Total soil respiration decreased in the order PST > SPS > PPP and leached C decreased in the order PPP > PST > SPS. In general, the mean annual soil moisture in the pasture alleys of SPS was twice that of PST. The air/soil temperatures decreased significantly in the second year only in PST and at 2 m and beyond from the tree strip in SPS. Soil moisture varied significantly among treatments, but showed the strong influence exerted by trees in the creation of a favorable microclimate within the pasture alleys of SPS.