N2O fluxes of a bio‐energy poplar plantation during a two years rotation period

Nitrous oxide emissions are of critical importance for the assumed climate neutrality of bio‐energy. In this study we report on the N₂O fluxes from a bio‐energy poplar plantation measured with eddy covariance for 2 years, after conversion of agricultural fields to few months after harvesting of the plantation. A pulse peak of N₂O was detected after the land use change and in the wake of the first heavy rainfall. The N₂O‐N emission during just a single week was 2.7 kg N₂O‐N ha^?1 which represented approximately 42% of the total N₂O‐N emitted during the 2 years of measurements. After this peak emission, N₂O fluxes were constantly rather low, not increasing after rainfall events any longer. Lowest emissions (and even N₂O sink) occurred mostly during the end of the second growing season with maximum canopy development, and water table deeper than 80 cm. Gross primary production (GPP) explained 68% of the monthly averaged variability in N₂O emission from August to December 2011. Probably N uptake by vegetation during the peak of the second growing season limited N₂O emission, which in fact increased again after the plantation was coppiced. For the majority of the measuring period, N₂O fluxes did not present a well‐defined diurnal pattern, with the exception of two periods: (1) from 19–22 August 2010 and (2) from September–November 2011. In both cases wind speed played a major role in controlling the diurnal pattern in these fluxes (explaining up to 80% of the diurnal variability in N₂O fluxes on 19–22 August 2010), whereas at the end of the second growing season (September–November 2011), GPP explained 73% of the diurnal pattern in N₂O fluxes.     

Transglutaminase activity changes during the hypersensitive reaction, a typical defense response of tobacco NN plants to TMV

The occurrence of glutamyl polyamines (PAs) and changes in activity and levels of transglutaminase (TGase, EC 2.3.2.13), the enzyme responsible for their synthesis, are reported during the progression of the hypersensitive reaction (HR) of resistant NN tobacco plants ( Nicotiana tabacum L. cv. Samsun) to tobacco mosaic virus (TMV). Mature leaves of tobacco were collected over 0–72 h after inoculation with TMV or phosphate buffer (mock). In vivo synthesis of polyamine glutamyl derivatives (glutamyl PAs), catalyzed by TGase activity, was evaluated after supplying labeled putrescine (Pu, a physiological substrate of TGase) to leaves. Results show that, starting from 24 h, mono-( γ -glutamyl)-Pu and bis-( γ -glutamyl)-Sd were recovered in TMV-inoculated samples but not in mock-inoculated ones; 2 days later, in the former, the amount of glutamyl derivatives further increased. An in vitro radiometric assay showed that, in TMV-inoculated leaves, TGase activity increased from 24 h onwards relative to mock controls. An immunoblot analysis with AtPng1p polyclonal antibody detected a 72-kDa protein whose amount increased at 72 h in TMV-inoculated leaves and in the lesion-enriched areas. A biotin-labeled cadaverine incorporation assay showed that TGase activity occurred in S1 (containing soluble proteins), S2 (proteins released by both cell walls and membranes) and S3 (membrane intrinsic proteins) fractions. In S3 fraction, where changes were the most relevant, TGase activity was enhanced in both mock-inoculated and TMV-inoculated samples, but the stimulation persisted only in the latter case. These data are discussed in the light of a possible role of TGase activity and glutamyl PAs in the defense against a viral plant pathogen.     

Met23Lys mutation in subunit gamma of F(O)F(1)-ATP synthase from Rhodobacter capsulatus impairs the activation of ATP hydrolysis by protonmotive force

H(+)-F(O)F(1)-ATP synthase couples proton flow through its membrane portion, F(O), to the synthesis of ATP in its headpiece, F(1). Upon reversal of the reaction the enzyme functions as a proton pumping ATPase. Even in the simplest bacterial enzyme the ATPase activity is regulated by several mechanisms, involving inhibition by MgADP, conformational transitions of the epsilon subunit, and activation by protonmotive force. Here we report that the Met23Lys mutation in the gamma subunit of the Rhodobacter capsulatus ATP synthase significantly impaired the activation of ATP hydrolysis by protonmotive force. The impairment in the mutant was due to faster enzyme deactivation that was particularly evident at low ATP/ADP ratio. We suggest that the electrostatic interaction of the introduced gammaLys23 with the DELSEED region of subunit beta stabilized the ADP-inhibited state of the enzyme by hindering the rotation of subunit gamma rotation which is necessary for the activation.     

Microbotanical Evidence of Domestic Cereals in Africa 7000 Years Ago

The study of plant exploitation and early use of cereals in Africa has seen over the years a great input from charred and desiccated macrobotanical remains. This paper presents the results of one of the few examples in Africa of microbotanical analyses. Three grave contexts of phytolith-rich deposits and the dental calculus of 20 individuals were analysed from two Neolithic cemeteries in North and Central Sudan. The radiocarbon-dated phytoliths from the burial samples show the presence of Near East domestic cereals in Northern Sudan at least 7000 years ago. Phytoliths also indicate the exploitation of wild, savannah-adapted millets in Central Sudan between 7500 and 6500 years ago. The calculus samples contained starch grains from wheat/barley, pulses and millets, as well as panicoid phytoliths. This evidence shows that Near East domestic cereals were consumed in Northern Africa at least 500 years earlier than previously thought.     

Dental Calculus Reveals Unique Insights into Food Items,Cooking and Plant Processing in Prehistoric Central Sudan

Accessing information on plant consumption before the adoption of agriculture is challenging. However, there is growing evidence for use of locally available wild plants from an increasing number of pre-agrarian sites, suggesting broad ecological knowledge. The extraction of chemical compounds and microfossils from dental calculus removed from ancient teeth offers an entirely new perspective on dietary reconstruction, as it provides empirical results on material that is already in the mouth. Here we present a suite of results from the multi-period Central Sudanese site of Al Khiday. We demonstrate the ingestion in both pre-agricultural and agricultural periods of Cyperus rotundus tubers. This plant is a good source of carbohydrates and has many useful medicinal and aromatic qualities, though today it is considered to be the world''s most costly weed. Its ability to inhibit Streptococcus mutans may have contributed to the unexpectedly low level of caries found in the agricultural population. Other evidence extracted from the dental calculus includes smoke inhalation, dry (roasting) and wet (heating in water) cooking, a second plant possibly from the Triticaceae tribe and plant fibres suggestive of raw material preparation through chewing.     

Human Hsp60 with Its Mitochondrial Import Signal Occurs in Solution as Heptamers and Tetradecamers Remarkably Stable over a Wide Range of Concentrations

It has been established that Hsp60 can accumulate in the cytosol in various pathological conditions, including cancer and chronic inflammatory diseases. Part or all of the cytosolic Hsp60 could be naïve, namely, bear the mitochondrial import signal (MIS), but neither the structure nor the in solution oligomeric organization of this cytosolic molecule has still been elucidated. Here we present a detailed study of the structure and self-organization of naïve cytosolic Hsp60 in solution. Results were obtained by different biophysical methods (light and X ray scattering, single molecule spectroscopy and hydrodynamics) that all together allowed us to assay a wide range of concentrations of Hsp60. We found that Naïve Hsp60 in aqueous solution is assembled in very stable heptamers and tetradecamers at all concentrations assayed, without any trace of monomer presence.     

Plastic responses of some life history traits and cellular components of body size in Aphidius ervi as related to the age of its host Acyrthosiphon pisum

Phenotypic plasticity of wing size and shape has been evaluated in Aphidius ervi developing in its host, Acyrthosiphon pisum, parasitized at seven different ages. The parasitoid wing size was used as an estimator of both whole body size and its cellular composition. No size difference was observed in A. ervi adults emerged from aphids 1, 2 or 3 days old at parasitization. Body size then increased in A. ervi emerged from hosts older at parasitization. Body size values as related to host age at parasitization were achieved by adjusting developmental time, developmental rate or both. Parasitoids of similar size, but developed in hosts parasitized at different ages, had different wing cellular composition, while the increase of parasitoid body size was related to a general increase in both cell area and cell number. These results seem to suggest a trade‐off between adult size and developmental time, at least for parasitoids developed at the two extremes of host ages at parasitization, and that A. ervi can reach the same adult size via different trajectories, adapting its ontogenetic processes. Wing shape was typical for all the different parasitoid classes considered and differed strongly between males and females, independent of their size. Parasitoid males (haploids) and females (diploids) did not differ in either cell area or cell number, suggesting a possible sex‐determined dosage compensation in somatic tissue endoreplication. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 439–454.     

Helianthus tuberosus and polyamine research: Past and recent applications of a classical growth model

The earliest studies concerning polyamines (PAs) in plants were performed by using in vitro cultured explants of Helianthus tuberosus dormant tuber. This parenchyma tissue was particularly useful due to its susceptibility to several growth substances, including PAs. During tuber dormancy, PA levels are too low to sustain cell division; thus Helianthus represents a natural PA-deficient model. When cultivated in vitro in the presence of auxins, Helianthus tuber dormant parenchyma cells at the G₀ stage start to divide synchronously acquiring meristematic characteristics. The requirement for auxins to induce cell division can be substituted by aliphatic PAs such as putrescine, spermidine or spermine. Cylinders or slices of explanted homogeneous tuber parenchyma were cultured in liquid medium for short-term studies on the cell cycle, or on solid agar medium for long-term experiments. Morphological and physiological modifications of synchronously dividing cells were studied during the different phases of the cell cycle in relation to PAs biosynthesis and oxidation. Long-term experiments led to the identification of the PAs as plant growth regulators, as the sole nitrogen source, as tuber storage substances and as essential factors for morphogenetic processes and cell homeostasis. More recently this system was used to study the effects on plant cell proliferation of platinum- or palladium-derived drugs (cisplatin and platinum or palladium bi-substituted spermine) that are used in human cancer cell lines as antiproliferative and cytotoxic agents. Cisplatin was the most active both in cell proliferation inhibition and on PA metabolism. Similar experiments were performed using three agmatine analogous. Different effects of these compounds were observed on cell proliferation, free PA levels and enzyme activities, leading to a hypothesis of a correlation between their chemical structure and the agmatine metabolism in plants.