Fertilization Events Research Articles

Activation of Src and release of intracellular calcium by phosphatidic acid during Xenopus laevis fertilization

We report a new step in the fertilization in Xenopus laevis which has been found to involve activation of Src tyrosine kinase to stimulate phospholipase C-γ (PLC-γ) which increases inositol 1,4,5-trisphosphate (IP3) to release intracellular calcium ([Ca]i). Molecular species analysis and mass measurements suggested that sperm activate phospholipase D (PLD) to elevate phosphatidic acid (PA). We now report that PA mass increased 2.7 fold by 1min after insemination and inhibition of PA production by two methods inhibited activation of Src and PLCγ, increased [Ca]i and other fertilization events. As compared to 14 other lipids, PA specifically bound Xenopus Src but not PLCγ. Addition of synthetic PA activated egg Src (an action requiring intact lipid rafts) and PLCγ as well as doubling the amount of PLCγ in rafts. In the absence of elevated [Ca]i, PA addition elevated IP3 mass to levels equivalent to that induced by sperm (but twice that achieved by calcium ionophore). Finally, PA induced [Ca]i release that was blocked by an IP3 receptor inhibitor. As only PLD1b message was detected, and Western blotting did not detect PLD2, we suggest that sperm activate PLD1b to elevate PA which then binds to and activates Src leading to PLCγ stimulation, IP3 elevation and [Ca]i release. Due to these and other studies, PA may also play a role in membrane fusion events such as sperm–egg fusion, cortical granule exocytosis, the elevation of phosphatidylinositol 4,5-bisphosphate and the large, late increase in sn 1,2-diacylglycerol in fertilization.

The cell biology of mammalian fertilization

Fertilization is the process by which eggs and spermatozoa interact, achieve mutual recognition, and fuse to create a zygote, which then develops to form a new individual, thus allowing for the continuity of a species. Despite numerous studies on mammalian fertilization, the molecular mechanisms underpinning the fertilization event remain largely unknown. However, as I summarize here, recent work using both gene-manipulated animals and in vitro studies has begun to elucidate essential sperm and egg molecules and to establish predictive models of successful fertilization.

Use of sex-sorted and unsorted frozen/thawed sperm and in vitro fertilization events in bovine oocytes derived from ultrasound-guided aspiration

The objective was to investigate the effects of sex-sorting on early fertilization events in ovum pick up (OPU) derived oocytes fertilized in vitro with frozen-thawed sperm at different co-incubation lengths. Eighty-four OPU sessions were carried out in 18 cyclic, dry and non-stimulated Holstein Friesian and German black pied cows. Ovum pick up oocytes were matured in vitro for 24 hours and fertilized with frozen-thawed sex sorted or unsorted sperm from the same ejaculate. Fertilization was achieved by two experimental protocols: 1) short gamete co-incubation length: 4, 8 and 12 hours; and 2) long gamete co-incubation length: 18 and 24 hours. After in vitro fertilization, ova were fixed and stained to identify early fertilization events. Sperm penetration, monospermy, pronuclear formation and syngamy did not differ, whether sexed or unsexed sperm was used. Overall, the findings demonstrate similar fertilizing potential between sex-sorted and unsorted sperm.

Influence of nitrogen fertiliser application and timing on greenhouse gas emissions from a lychee (Litchi chinensis) orchard in humid subtropical Australia

Nitrous oxide emissions from intensive, fertilised agricultural systems have been identified as significant contributors to both Australia's and the global greenhouse gas (GHG) budget. This is expected to increase as rates of agriculture intensification and land use change accelerate to support population growth and food production. Limited data exists on N2O trace gas fluxes from subtropical or tropical tree cropping soils critical for the development of effective mitigation strategies.This study aimed to quantify GHG emissions over two consecutive years (March 2007 to March 2009) from a 30 year (lychee) orchard in the humid subtropical region of Australia. GHG fluxes were measured using a combination of high temporal resolution automated sampling and manually sampled chambers. No fertiliser was added to the plots during the 2007 measurement season. A split application of nitrogen fertiliser (urea) was added at the rate of 265kgNha−1 during the autumn and spring of 2008. Emissions of N2O were influenced by rainfall events and seasonal temperatures during 2007 and the fertilisation events in 2008. Annual N2O emissions from the lychee canopy increased from 1.7kgN2O–Nha−1yr−1 for 2007, to 7.6kgN2O–Nha−1yr−1 following fertiliser application in 2008. This represented an emission factor of 1.56%, corrected for background emissions. The timing of the split application was found to be critical to N2O emissions, with over twice as much lost following an application in spring (2.44%) compared to autumn (EF: 1.10%). This research suggests that avoiding fertiliser application during the hot and moist spring/summer period can reduce N2O losses without compromising yields.

Open sea hydrographic forcing of nutrient and phytoplankton dynamics in a Mediterranean coastal ecosystem

The dynamics of inorganic nutrients and phytoplankton was studied along two transects located in the coastal area of Barcelona (NW Mediterranean), from March 2002 to March 2006. Similar seasonal variability patterns were observed in the four annual cycles and in general, the nutrient concentrations were highest in winter and lowest in summer. Two phytoplankton peaks, composed mainly by diatoms and nanoflagellates, were generally detected during the year with the main peak during winter-early spring, linked to different fertilization mechanisms, and a secondary peak generally found in autumn, probably related both to the new availability of nutrients due to the disruption of the thermocline and to freshwater inputs. During the rest of the year, with a stratified water column and low nutrient concentrations, phytoplankton remained at a low abundance and comprised mainly small dinoflagellates, although there was smaller scale variability conditioned by rainfall events and subsequent freshwater discharges. Despite the similarity of the seasonal patterns, there were interannual changes in origin of new nutrient inputs into the coastal zone and in the taxonomic composition of the winter-early spring phytoplankton maxima. The main source of nutrients for the winter-early spring maxima of 2003 and 2004 was river runoff, while fertilization events in the two following winters were mainly due to the intrusion, onto the Barcelona shelf, of intermediate waters in 2005, and of surface offshore waters, which also carried a different phytoplankton community, in 2006. These changes were linked to unusually cold and dry weather in the winters of 2005 and 2006, which resulted in strong vertical mixing and deep water formation events in the NW Mediterranean basin. The overall amount of nutrients provided to the coastal zone by offshore water fertilization was higher (2005) or equal (2006) than that provided by freshwater inputs in 2003 and 2004. Our findings highlight the importance of identifying the different sources of nutrients in understanding the dynamics of phytoplankton and for devising management strategies of the coastal environment.

Molecular dissection of IZUMO1, a sperm protein essential for sperm-egg fusion

Although the membrane fusion of spermatozoon and egg cells is the central event of fertilization, the underlying molecular mechanism remains virtually unknown. Gene disruption studies have showed that IZUMO1 on spermatozoon and CD9 on oocyte are essential transmembrane proteins in sperm-egg fusion. In this study, we dissected IZUMO1 protein to determine the domains that were required for the function of sperm-egg fusion. We found that a fragment of the N terminus (Asp5 to Leu113) interacts with fertilization inhibitory antibodies. It also binds to the egg surface and effectively inhibits fusion in vitro. We named this fragment 'IZUMO1 putative functional fragment (IZUMO1PFF)'. Surprisingly, IZUMO1PPF still maintains binding ability on the egg surface of Cd9(-/-) eggs. A series of biophysical measurements using circular dichroism, sedimentation equilibrium and small angle X-ray scattering revealed that IZUMO1PFF is composed of an N-terminal unfolded structure and a C-terminal ellipsoidal helix dimer. Egg binding and fusion inhibition were not observed in the IZUMO1PFF derivative, which was incapable of helix formation. These findings suggest that the formation of a helical dimer at the N-terminal region of IZUMO1 is required for its function. Cos-7 cells expressing the whole IZUMO1 molecule bound to eggs, and IZUMO1 accumulated at the interface between the two cells, but fusion was not observed. These observations suggest that IZUMO1 alone cannot promote sperm-egg membrane fusion, but it works as a factor that is related to the cellular surface interaction, such as the tethering of the membranes by a helical region corresponding to IZUMO1PFF-core.

The timing of monozygotic twinning: a criticism of the common model

In the dominant model, monozygotic (MZ) twinning is universally accepted as a post-fertilization event resulting from splitting of the embryo along its first 2 weeks of development. The stage at which splitting occurs determines chorionicity and amnionicity. A short history on how the model was built is presented, stressing the role played by some embryologists, in particular George Corner, in its completion and final success. Strikingly, for more than 60 years no deep criticisms have been raised against the model, which, in virtue of its rational and plausible character, enjoys the status of undisputed truth. At close examination, the embryological support of the model shows some important weak points, particularly when dealing with late splitting. In the author's view, the model not only has contributed to 'suspend' our knowledge on the timing of MZ twinning, but seems indefensible and claims to be substituted. That factor could imply relevant consequences for embryology and bioethics. As an alternative to the model, a new theory to explain the timing of MZ twinning is proposed. It is based on two premises. First, MZ twinning would be a fertilization event. In that case, due to an alteration of the zygote-blastomere transition, the first zygotic division, instead of producing two blastomeres, generates twin zygotes. Second, monochorionicity and monoamnionicity would not depend on embryo splitting, but on fusion of membranes. Some support for this theory can be found in recent embryological advances and also in some explanations of old.

Detection of photoactive siderophore biosynthetic genes in the marine environment

Iron is an essential element for oceanic microbial life but its low bioavailability limits microorganisms in large areas of the oceans. To acquire this metal many marine bacteria produce organic chelates that bind and transport iron (siderophores). While it has been hypothesized that the global production of siderophores by heterotrophic bacteria and some cyanobacteria constitutes the bulk of organic ligands binding iron in the ocean because stability constants of siderophores and these organic ligands are similar, and because ligand concentrations rise sharply in response to iron fertilization events, direct evidence for this proposal is lacking. This lack is due to the difficulty in characterizing these ligands due both to their extremely low concentrations and their highly heterogeneous nature. The situation for characterizing photoactive siderophores in situ is more problematic because of their expected short lifetimes in the photic zone. An alternative approach is to make use of high sensitivity molecular technology (qPCR) to search for siderophore biosynthesis genes related to the production of photoactive siderophores. In this way one can access their "biochemical potential" and utilize this information as a proxy for the presence of these siderophores in the marine environment. Here we show, using qPCR primers designed to detect biosynthetic genes for the siderophores vibrioferrin, petrobactin and aerobactin that such genes are widespread and based on their abundance, the "biochemical potential" for photoactive siderophore production is significant. Concurrently we also briefly examine the microbial biodiversity responsible for such production as a function of depth and location across a North Atlantic transect.

Moments of induced spawning and embryonic development of Brycon amazonicus (Teleostei, Characidae)

Based on the economic and ecological relevance of Brycon amazonicus, the goal of this work was to describe the diameter of oocytes and eggs of this species, as well as the chronological embryonic development. The material was provided by Buriti fish farm, Nova Mutum - MT, Brazil. Samples of both oocytes and eggs were obtained from extrusion to hatching. The material was fixed and measured under stereomicroscope, and the samples were divided for light microscopy or scanning electron microscopy (SEM) analyses. At extrusion, the oocytes were bluish green. The frequency distribution of oocytes revealed that 87.7% of them ranged from 1.11-1.30 mm in diameter. During incubation, the total diameter of the eggs increased from 1.22 ± 0.04 mm to 3.06 ± 0.46 mm in the first 60 min post fertilization (PF), and growth ceased at 180 min PF. Between 10-30 s PF, most eggs were fertilized and fertilization cones were observed from 10 s onwards after gamete activation. The main fertilization events took place asynchronically and spermatozoa were visualized in the micropyle vestibule up to 90 s PF. The first cell was formed in the centre of the blastodisc 20 min PF. The morula stage was identified 2 h PF and, 3 h later, 70% of the yolk was covered by the blastoderm; the blastopore was almost entirely closed at 6 h PF. The cephalic and caudal regions of the embryo could be defined 8 h PF and hatching occurred after 13 h of embryonic development. The larvae hatched with undifferentiated organic systems and with a large yolk sac, free from swimming abilities or visual acuity.

Reduced nitrous oxide emissions and increased yields in California tomato cropping systems under drip irrigation and fertigation

Understanding the effect of various agricultural management practices on nitrous oxide (N2O) emissions is crucial to advise farmers and formulate policies for future greenhouse gas (GHG) reductions. In order to estimate present N2O emissions, annual N2O budgets must be thoroughly and precisely quantified from current farms under conventional and alternative management, but subject to practical and economic constraints. In this study, field sites were located on two on-farm processing tomato (Lycopersicon esculentum) fields, under contrasting irrigation managements and their associated fertilizer application strategy: (1) furrow irrigation and sidedress fertilizer injection (conventional system) and (2) drip irrigation, reduced tillage, and fertigation (integrated system). Nitrous oxide emissions were monitored for seven to ten days following major events of cultivation, irrigation, fertilization, harvest, and winter precipitations. Total weighted growing season emissions (15 March–1 November 2010) were 2.01±0.19kgN2O-Nha−1 and 0.58±0.06kgN2O-Nha−1 in the conventional and integrated systems, respectively. The highest conventional system N2O emission episodes resulted from fertilization plus irrigation events and the first fall precipitation. In the integrated system, the highest N2O fluxes occurred following harvest and the first fall precipitation. Soil chemical and physical properties of soil moisture, inorganic nitrogen (N), and dissolved organic carbon (DOC) were low and less spatially variable in the integrated system. Used as an index of substrate availability, soil ammonium (NH4+) and nitrate (NO3−) exposures were significantly lower in the integrated system. Of great importance is that the drip irrigation water and fertilizer management of the integrated system also increased crop yield (119Mgha−1 vs. 78Mgha−1), highlighting the potential for decreasing N2O emissions while simultaneously improving the use of water and fertilizer for plant production.

MAP18 Regulates the Direction of Pollen Tube Growth in Arabidopsis by Modulating F-Actin Organization

For fertilization to occur in plants, the pollen tube must be guided to enter the ovule via the micropyle. Previous reports have implicated actin filaments, actin binding proteins, and the tip-focused calcium gradient as key contributors to polar growth of pollen tubes; however, the regulation of directional pollen tube growth is largely unknown. We reported previously that Arabidopsis thaliana MICROTUBULE-ASSOCIATED PROTEIN18 (MAP18) contributes to directional cell growth and cortical microtubule organization. The preferential expression of MAP18 in pollen and in pollen tubes suggests that MAP18 also may function in pollen tube growth. In this study, we demonstrate that MAP18 functions in pollen tubes by influencing actin organization, rather than microtubule assembly. In vitro biochemical results indicate that MAP18 exhibits Ca(2+)-dependent filamentous (F)-actin-severing activity. Abnormal expression of MAP18 in map18 and MAP18 OX plants was associated with disorganization of the actin cytoskeleton in the tube apex, resulting in aberrant pollen tube growth patterns and morphologies, inaccurate micropyle targeting, and fewer fertilization events. Experiments with MAP18 mutants created by site-directed mutagenesis suggest that F-actin-severing activity is essential to the effects of MAP18 on pollen tube growth direction. Our study demonstrates that in Arabidopsis, MAP18 guides the direction of pollen tube growth by modulating actin filaments.

Heparin and Heparin Binding Proteins: Potential Relevance to Reproductive Physiology

Glycosaminoglycans (GAGs) have crucial roles in cell-cell interaction and communication. The communication between sperm and egg during fertilization is the finest example of intercellular communication involving a protein-carbohydrate recognition system. GAGs, especially heparin, are implicated in various processes, such as capacitation, acrosome reaction (AR), and sperm nuclei decondensation by interacting with a wide range of proteins, leading to fertilization. Seminal plasma (SP) comprises of multiple proteins that bind to heparin and related GAGs. Heparin binding proteins (HBPs) originating from secretions of the male accessory sex glands are known to play a vital role during fertilization events. They interact with GAGs present in the female genital tract and enhance the subsequent zona pellucida-induced AR, and thus have been correlated with fertility in some species. Several carbohydrate and zona pellucida-binding proteins, many of which belong to the spermadhesin family, are identified as HBPs. Many studies have been documented about the potential physiological role of some HBPs in various steps of fertilization. However, there is insufficient knowledge about functions executed by various HBPs and their exact mechanism and pathways. An in-depth knowledge of HBPs and their role in fertilization is of fundamental importance to resolve biological pathways and protein interactions at the molecular level. This review surveys some of the relevant findings supporting the potential role of heparin and HBPs in reproduction. It also describes consensus heparin binding sites emerging from known literature on HBPs that interact with heparin.

The natural ocean acidification and fertilization event caused by the submarine eruption of El Hierro

The shallow submarine eruption which took place in October 10th 2011, 1.8 km south of the island of El Hierro (Canary Islands) allowed the study of the abrupt changes in the physical-chemical properties of seawater caused by volcanic discharges. In order to monitor the evolution of these changes, seven oceanographic surveys were carried out over six months (November 2011-April 2012) from the beginning of the eruptive stage to the post-eruptive phase. Here, we present dramatic changes in the water column chemistry including large decreases in pH, striking effects on the carbonate system, decreases in the oxygen concentrations and enrichment of Fe(II) and nutrients. Our findings highlight that the same volcano which was responsible for the creation of a highly corrosive environment, affecting marine biota, has also provided the nutrients required for the rapid recuperation of the marine ecosystem.

Increased Maternal Genome Dosage Bypasses the Requirement of the FIS Polycomb Repressive Complex 2 in Arabidopsis Seed Development

Seed development in flowering plants is initiated after a double fertilization event with two sperm cells fertilizing two female gametes, the egg cell and the central cell, leading to the formation of embryo and endosperm, respectively. In most species the endosperm is a polyploid tissue inheriting two maternal genomes and one paternal genome. As a consequence of this particular genomic configuration the endosperm is a dosage sensitive tissue, and changes in the ratio of maternal to paternal contributions strongly impact on endosperm development. The FERTILIZATION INDEPENDENT SEED (FIS) Polycomb Repressive Complex 2 (PRC2) is essential for endosperm development; however, the underlying forces that led to the evolution of the FIS-PRC2 remained unknown. Here, we show that the functional requirement of the FIS-PRC2 can be bypassed by increasing the ratio of maternal to paternal genomes in the endosperm, suggesting that the main functional requirement of the FIS-PRC2 is to balance parental genome contributions and to reduce genetic conflict. We furthermore reveal that the AGAMOUS LIKE (AGL) gene AGL62 acts as a dosage-sensitive seed size regulator and that reduced expression of AGL62 might be responsible for reduced size of seeds with increased maternal genome dosage.

Comparison between static chamber and tunable diode laser-based eddy covariance techniques for measuring nitrous oxide fluxes from a cotton field

Nitrous oxide (N2O) fluxes from a cotton field in northern China were measured for a year using the static chamber method based on a gas chromatograph (GC) and the eddy covariance (EC) technique based on a tunable diode laser (TDL). The aims were to compare the N2O fluxes obtained from both techniques, assess the uncertainties in the fluxes and evaluate the annual direct emission factors (EFds, i.e. the loss rate of fertilizer nitrogen via N2O emission) using the year-round datasets. During the experimental period, the hourly and daily mean chamber fluxes ranged from 0.6 to 781.8 and from 1.2 to 468.8μgNm−2h−1, respectively. The simultaneously measured daily mean EC fluxes varied between −10.8 and 912.0μgNm−2h−1. The EC measurements only provided trustworthy 30-min fluxes during high-emission period (a 20-day period immediately after the irrigation that followed the nitrogen fertilization event). A reliable comparison was confined to the high-emission period and showed that the chamber fluxes were 17–20% lower than the EC fluxes. This difference may implicate the magnitude of systematic underestimation in the fluxes from chamber measurements. The annual emission from the fertilized cotton field was estimated at 1.43kgNha−1yr−1 by the chamber observations and 3.15kgNha−1yr−1 by the EC measurements. The EFds calculated from the chamber and EC data were 1.04% and 1.65%, respectively. The chamber-based estimate was very close to the default value (1.0%) recommended by the Intergovernmental Panel on Climate Change. However, the difference in the EFds based on the two measurement techniques may vary greatly with changing environmental conditions and management practices. Further comparison studies are still needed to elucidate this issue.

263 DESCRIPTION OF CORTICAL GRANULE DISTRIBUTION IN OVINE MATURED OOCYTES: PRELIMINARY RESULTS

In mammalian oocytes, the migration of cortical granules (CG) is an important step in cytoplasmic maturation and has been used as a criterion in the assessment of maturity and organelle organisation. With the use of fluorescent lectins, it is possible to identify specific sugars originating from the CG and to localise them to the oolemma, within the perivitelline space, or both. To our knowledge, no reports are available on fluorescence assessment of CG organisation in ovine oocytes. Therefore, the aim of this study was to describe the CG distribution of ovine oocytes after in vitro maturation (IVM). One hundred twenty-five oocytes from adults ewes were submitted to IVM in TCM-199 medium supplemented with 10% FBS for 24 h. The denuded oocytes were immersed in 0.1% pronase for 5 min to dissolve the zona pellucidae, fixed in 3% paraformaldehyde for 30 min, and incubated overnight in blocking solution at 4°C. Oocytes were placed into 0.1% Triton X-100 for 5 min for permeabilization and incubated in 10 µg mL–1 of fluorescent Lens culinaris agglutinin–fluorescein complex for 15 min at 37°C before being rinsed and mounted onto histological slides. The distribution of CG was evaluated with an Olympus fluorescence microscope (wavelength: 420 to 490 nm; Olympus, Tokyo, Japan), and oocytes were classified into three types according to the observed distributional pattern of the CG: (I) aggregates of CG distributed over the entire cytoplasm, (II) CG distributed in the cortex and forming a fluorescent halo around the plasma membrane, and (III) CG distributed uniformly over the entire cytoplasm without the presence of aggregates. Proportions of oocyte types were analysed by chi-square or, when appropriate, by Fisher’s exact test, using SAS version 8.2 (SAS Institute Inc., Cary, NC, USA). The proportion of type III oocytes (98/125, 78.4%) was significantly higher (P < 0.05) than those of types I (10/125, 8%) and II (17/125, 13.6%). No significant difference was observed between the proportions of type I and II oocytes. Analogous with the results described in the bovine, the type I distribution of CG in ovine oocytes has been considered a sign of a lack of maturation, even if the aggregates of CG are not as evident as in the bovine; types II and III were considered mature oocytes based on the cortical migration of CG. The cytoplasmic maturation is an essential process in directing and supporting the events of fertilization and early embryonic development. Therefore, describing the species-specific pattern of CG distribution is important for the assessment of oocyte maturation. More studies in the ovine are necessary to confirm the correlation between CG distribution and maturation status, as in bovine species.

Comprehensive mapping of the bull sperm surface proteome

While the mechanisms that underpin maturation, capacitation, and sperm-egg interactions remain elusive it is known that these essential fertilisation events are driven by the protein complement of the sperm surface. Understanding these processes is critical to the regulation of animal reproduction, but few studies have attempted to define the full repertoire of sperm surface proteins in animals of agricultural importance. Recent developments in proteomics technologies, subcellular fractionation, and optimised solubilisation strategies have enhanced the potential for the comprehensive characterisation of the sperm surface proteome. Here we report the identification of 419 proteins from a mature bull sperm plasma membrane fraction. Protein domain enrichment analyses indicate that 67% of all the proteins identified may be membrane associated. A large number of the proteins identified are conserved between mammalian species and are reported to play key roles in sperm-egg communication, capacitation and fertility. The major functional pathways identified were related to protein catabolism (26S proteasome complex), chaperonin-containing TCP-1 (CCT) complex and fundamental metabolic processes such as glycolysis and energy production. We have also identified 118 predicted transmembrane proteins, some of which are implicated in cell adhesion, acrosomal exocytosis, vesicle transport and immunity and fertilisation events, while others have not been reported in mammalian LC-MS-derived sperm proteomes to date. Comparative proteomics and functional network analyses of these proteins expand our system's level of understanding of the bull sperm proteome and provide important clues toward finding the essential conserved function of these proteins.

Fertilization affects severity of disease caused by fungal plant pathogens

Commercial fertilizers are commonly applied in farming to maximize crop yield. Lifting nutrient limitation to plant growth when water and light conditions are sufficient may permit plants to grow to the maximum of their ability; however, plant ability to resist pathogen infections is also modified. A meta‐analysis was conducted on 57 articles to identify the way plant disease severity of fungal pathogen‐induced infection is modified following fertilization, and the key regulators of such an effect. The analysis largely focused on N fertilization events in order to minimize the effect of heterogeneity that could result from differences in the way different nutrient fertilizers are able to modify plant disease severity. Fungal pathogen identity and fungal pathogen lifestyle were the main significant regulators affecting the extent of the modification of plant disease resistance following N fertilization, whereas contradictory results were obtained with the susceptibility of plant species. No differences were detected between pot or field experiments and following artificial or natural infection. Although in the vast majority of instances N fertilization increased disease severity, characteristic plant species and fungal pathogens could be identified for which disease severity following N fertilization declined. It is concluded that the potential of some plant species such as Solanum spp. to show reduced disease severity following N fertilization requires further investigation, as in such cases N fertilization could potentially be used as an additional means of suppressing fungal pathogens.

Soil Greenhouse Gas Emissions Affected by Irrigation, Tillage, Crop Rotation, and Nitrogen Fertilization

Management practices, such as irrigation, tillage, cropping system, and N fertilization, may influence soil greenhouse gas (GHG) emissions. We quantified the effects of irrigation, tillage, crop rotation, and N fertilization on soil CO, NO, and CH emissions from March to November, 2008 to 2011 in a Lihen sandy loam in western North Dakota. Treatments were two irrigation practices (irrigated and nonirrigated) and five cropping systems (conventional-tilled malt barley [ L.] with N fertilizer [CT-N], conventional-tilled malt barley with no N fertilizer [CT-C], no-tilled malt barley-pea [ L.] with N fertilizer [NT-PN], no-tilled malt barley with N fertilizer [NT-N], and no-tilled malt barley with no N fertilizer [NT-C]). The GHG fluxes varied with date of sampling and peaked immediately after precipitation, irrigation, and/or N fertilization events during increased soil temperature. Both CO and NO fluxes were greater in CT-N under the irrigated condition, but CH uptake was greater in NT-PN under the nonirrigated condition than in other treatments. Although tillage and N fertilization increased CO and NO fluxes by 8 to 30%, N fertilization and monocropping reduced CH uptake by 39 to 40%. The NT-PN, regardless of irrigation, might mitigate GHG emissions by reducing CO and NO emissions and increasing CH uptake relative to other treatments. To account for global warming potential for such a practice, information on productions associated with CO emissions along with NO and CH fluxes is needed.

Progesterone through progesterone receptors affects survival and metabolism of pig sperm

Progesterone receptors (PR) through interaction with the specific ligand progesterone (PRG), play a central coordinate role in different reproductive events. In this study conventional PR were identified in boar spermatozoa by Western blotting. Immunofluorescence techniques indicate that PR are located at sperm acrosomal region, suggesting a possible role in the oocyte fertilization events. Treatment with 17-hydroxyprogesterone (17-OHP) enhanced viability and induced cholesterol efflux, serine and tyrosine phosphorylation, p-Bcl2, p-Akt that are known hallmarks of capacitation in sperm. The analysis of the triglyceride contents, lipase and acyl-CoA dehydrogenase activities, as well as the G6PDH activity, was conducted so as to address whether there was an increase in energy expenditure via 17-OHP through the PR.Taken together these results, particularly the 17-OHP action on boar sperm lipid and glucose metabolism, give emphasis to the role of PR in sperm physiology within the oviductal environment. Moreover the present study highlights, the effect of PRG via PR on boar sperm survival, renewing the role of this hormone in male reproduction as candidate for boar fertility. Thus the present research contributes to further elucidating the role of progesterone on the physiological regulation of the most relevant spermatozoa functions for a successful fertilization.