Ecological functioning in grass–shrub Mediterranean ecosystems measured by eddy covariance

Climate change may alter ecosystem functioning, as assessed via the net carbon (C) exchange (NEE) with the atmosphere, composed of the biological processes photosynthesis (GPP) and respiration (R _eco). In addition, in semi-arid Mediterranean ecosystems, a significant fraction of respired CO₂ is stored in the vadose zone and emitted afterwards by subsoil ventilation (VE), contributing also to NEE. Such conditions complicate the prediction of NEE for future change scenarios. To evaluate the possible effects of climate change on annual NEE and its underlying processes (GPP, R _eco and VE) we present, over a climate/altitude range, the annual and interannual variability of NEE, GPP, R _eco and VE in three Mediterranean sites. We found that annual NEE varied from a net source of around 130 gC m^?2 in hot and arid lowlands to a net sink of similar magnitude for alpine meadows (above 2,000 m a.s.l) that are less water stressed. Annual net C fixation increased because of increased GPP during intermittent and several growth periods occurring even during winter, as well as due to decreased VE. In terms of interannual variability, the studied subalpine site behaved as a neutral C sink (from emission of 49 to fixation of 30 gC m^?2 year^?1), with precipitation as the main factor controlling annual GPP and R _eco. Finally, the importance of VE as 0–23 % of annual NEE is highlighted, indicating that this process could shift some Mediterranean ecosystems from annual C sinks to sources.     

Comparison of biomass production and total lipid content of freshwater green microalgae cultivated under various culture conditions

The growth and total lipid content of four green microalgae (Chlorella sp., Chlorella vulgaris CCAP211/11B, Botryococcus braunii FC124 and Scenedesmus obliquus R8) were investigated under different culture conditions. Among the various carbon sources tested, glucose produced the largest biomass or microalgae grown heterotrophically. It was found that 1 % (w/v) glucose was actively utilized by Chlorella sp., C. vulgaris CCAP211/11B and B. braunii FC124, whereas S. obliquus R8 preferred 2 % (w/v) glucose. No significant difference in biomass production was noted between heterotrophic and mixotrophic (heterotrophic with light illumination/exposure) growth conditions, however, less production was observed for autotrophic cultivation. Total lipid content in cells increased by approximately two-fold under mixotrophic cultivation with respect to heterotrophic and autotrophic cultivation. In addition, light intensity had an impact on microalgal growth and total lipid content. The highest total lipid content was observed at 100 μmol m^?2s^?1 for Chlorella sp. (22.5 %) and S. obliquus R8 (23.7 %) and 80 μmol m^?2s^?1 for C. vulgaris CCAP211/11B (20.1 %) and B. braunii FC124 (34.9 %).     

Molecular recognition between a new pentacyclic acridinium salt and DNA sequences investigated by optical spectroscopic techniques, proton nuclear magnetic resonance spectroscopy, and molecular modeling.

A pentacyclic acridine, 1H-2,3-dihydroindolizino[7,6,5-kl]acridinium chloride (1), related in structure to tetra- and pentacyclic marine natural products, has previously been shown to induce apoptosis in breast and non-small-cell lung tumor cell lines and shows significant differences in biological potency and antitumor profile from other intercalating agents based on the acridine framework. We report on the molecular recognition of the acridinium salt with DNA, quantified by optical spectroscopic methods, and have compared these results with the clinical agent amsacrine (m-AMSA). The results point to an intercalative association between 1 and G-C-rich sequences of DNA. We have synthesized a hexamer duplex d(ACGCGT)2, presenting two potential 5'-CpG recipient sites, and have investigated in detail by NMR and molecular modeling methods the orientational preferences of 1, particularly with regard to the pyrrolidine ring system. On the basis of the intermolecular nuclear Overhauser effect (NOE) data, four possible intercalation models were considered; no single model produced a significantly better fit than any of the others. The best fit to the experimental data was obtained by considering a dynamic equilibrium between the different intercalated orientations with the drug maximizing pi-overlap with the G-C base pairs at the intercalation site. We found little evidence for any degree of groove specificity imparted by the pyrrolidine ring. If these simulations have biological relevance they suggest that, at most, the agent induces only a transitory hot spot in the DNA which, evidently, is sufficient to be sensed by damage-recognition mechanisms of the cell.     

Analysis of cell cycle in root meristems

We have analyzed the cell proliferation in a meristem assuming a single file model for root architecture. The meristem file appears to be built up by two clearly separated zones: the first going from the initial cell to the middle of the meristem and the second from the middle to the meristem boundary. The first half of the meristem shows an exponential age distribution for the cell population. In contrast, in the second half of the meristem, the cell kinetics of cycling cells strongly disagree with exponential kinetics and due to the compensation between the observed deviations in both halves, cell supply in the file meristem is in line with linear kinetics. However, we proposed that exponential kinetic equations offer a suitable approach to problems of cell cycle compartments and population age distributions in real meristems, where non-cycling cells cannot be identified inside the meristem, whether we consider the meristem as a whole or study a “window” inside it. Nevertheless, for more exact kinetic analysis, when estimating the proliferative fraction, the width of the “window” and its location along the axis must carefully be taken into account.     

Daily Activity Patterns and Thermal Tolerance of Three Sympatric Dung Beetle Species (Scarabaeidae: Scarabaeinae: Eucraniini) from the Monte Desert,Argentina

Tolerance to extreme temperatures, thermal limits, and the mechanisms of thermoregulation are related to internal functions of insects and partly define their ecological niche. We study the association between daily activity of dung beetles from the Monte Desert in Argentina and their tolerance to high temperatures. Results indicate that for all three sympatric species studied, Eucranium belenae Ocampo, Anomiopsoides cavifrons (Burmeister), and Anomiopsoides fedemariai Ocampo, daily activity is associated to ground temperature. Eucranium belenae is active when ground temperature is relatively low and it is less tolerant to long periods of activity at high temperatures in the lab, while A. cavifrons and A. fedemariai are active when ground temperatures are higher, and they tolerate high temperatures for longer periods of time than E. belenae in the lab. These species coexist and use similar food sources, and this eco-physiological study may help to explain how they differentiate under the same environmental conditions. The Monte Desert is considered an extreme environment, and studies on thermal tolerance offer testable predictions to understand how species would respond to climate change.     

Gonad characterization and reproductive seasonality in Siphonaria lessonii (Gastropoda: Heterobranchia) from the southwestern Atlantic Ocean

Histological characterization of the hermaphroditic gonad (HG) and seasonality of gametogenesis were investigated in a population of Siphonaria lessonii from the coast of Buenos Aires Province (37°16′S, 56°58′W). Monthly analysis of the frequency of gametogenic stages, as well as the number and mean size of oocytes, were used to determine reproductive events over a 2‐year period (June 2012–May 2014). Female and male gametes were observed simultaneously within acini of adult individuals and continuously throughout the period studied. Oogenesis commenced in the beginning of austral autumn, with gonads characterized mainly by proliferation of female cells. From this moment, oocytes gradually increased in number and area until spring, when a large number of individuals were found in the evacuation stage. The same trend was observed from early gonad maturation to advanced stages, indicating that gonad development was closely related to the frequency of oocyte stages and to the area (size) of oocytes. Spermatogenesis was also observed as a continuous process throughout the year, although spent acini were more frequent from November until February. Reproductive seasonality and gametogenesis were associated with changes in temperature and day length.     

Relationship between land uses and diversity of dung beetles (Coleoptera: Scarabaeinae) in the southern Atlantic forest of Argentina: which are the key factors?

The loss of natural habitats is one of the main drivers of biodiversity decline. Anthropogenic land uses preserving biotic and abiotic conditions of the native ecosystem are more suitable to preserve the native biodiversity. In this study, we explored changes in species richness and composition in different land uses of the southern Atlantic forest, considering three independent factors: (1) canopy (presence–absence), (2) type of vegetation (native–exotic) and (3) livestock (presence–absence). We expected a gradient of response in the richness and composition of the native forest dung beetle community, from land uses preserving canopy and native vegetation to open land uses with exotic vegetation. Dung beetles were sampled in protected native forests and four land uses, using two potential food resources: human dung and carrion. The species richness and composition of each habitat, as well as differences in composition and the influence of factors over diversity, were then analyzed. As expected, our results showed that land uses preserving canopy and native vegetation maintain the dung beetle diversity of the native forest. Moreover, while the three factors analyzed influenced dung beetle diversity, canopy cover was the main driver of dung beetle diversity loss. The main conclusion of this study is that the conservation of canopy (either native or exotic) is determinant to preserve highly diverse dung beetle communities and subsequently, the ecological functions performed by this taxon. However, the ecophysiological mechanism behind the response of dung beetles to habitat disturbance is poorly understood.     

Low‐gluten,nontransgenic wheat engineered with CRISPR/Cas9

Coeliac disease is an autoimmune disorder triggered in genetically predisposed individuals by the ingestion of gluten proteins from wheat, barley and rye. The α‐gliadin gene family of wheat contains four highly stimulatory peptides, of which the 33‐mer is the main immunodominant peptide in patients with coeliac. We designed two sgRNAs to target a conserved region adjacent to the coding sequence for the 33‐mer in the α‐gliadin genes. Twenty‐one mutant lines were generated, all showing strong reduction in α‐gliadins. Up to 35 different genes were mutated in one of the lines of the 45 different genes identified in the wild type, while immunoreactivity was reduced by 85%. Transgene‐free lines were identified, and no off‐target mutations have been detected in any of the potential targets. The low‐gluten, transgene‐free wheat lines described here could be used to produce low‐gluten foodstuff and serve as source material to introgress this trait into elite wheat varieties.