Land application of compost has been a promising remediation strategy for soil health and environmental quality, but substantial emissions of greenhouse gases, especially N2O, need to be controlled ...during making and using compost of high N-load wastes, such as chicken manure. Biochar as a bulking agent for composting has been proposed as a novel approach to solve this issue, due to large surface area and porosity, and thus high ion exchange and adsorption capacity. Here, we compared the impacts of biochar-chicken manure co-compost (BM) and chicken manure compost (M) on soil biological properties and processes in a 120-d microcosm experiment at the soil moisture of 60% water-filled pore space. Our results showed that BM and M addition significantly enhanced soil total C and N, inorganic and KCl-extractable organic N, microbial biomass C and N, cellulase enzyme activity, abundance of N2O-producing bacteria and fungi, and gas emissions of N2O and CO2. However, compared to the M treatment, BM significantly reduced soil CO2 and N2O emissions by 35% and 27%, respectively, over the experimental period. The 15N-N2O site preference, i.e., difference between 15N-N2O in the center position (δ15Nα) and the end position (δ15Nβ), was ∼17‰ for M and ∼26‰ for BM during the first week of incubation, suggesting that BM suppressed N2O from bacterial denitrification and/or nitrifier denitrification. This inference was well aligned with the observation that soil glucosaminidase activity and nirK gene abundance were lower in BM than M treatment. Further, soil peroxidase activity was greater in BM than M treatment, implying soil organic C was more stable in BM treatment. Our data demonstrated that the biochar-chicken manure co-compost could substantially reduce soil N2O emissions compared to chicken manure compost, via controls on soil organic C stabilization and the activities of microbial functional groups, especially bacterial denitrifiers.
•Impacts of biochar-manure (BM) compost on soil N processes were studied.•BM significantly reduced soil CO2 and N2O emissions compared to manure compost.•15N-N2O site preference suggested N2O reduction from bacterial denitrification.•This correlated to lower nirK gene abundance but higher peroxidase activity in BM.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Stomata are specialized epidermal structures that regulate gas (CO₂ and O₂) and water vapor exchange between plants and their environment. In Arabidopsis thaliana, stomatal development is preceded by ...asymmetric cell divisions, and stomatal distribution follows the one-cell spacing rule, reflecting the coordination of cell fate specification. Stomatal development and patterning are regulated by both genetic and environmental signals. Here, we report that Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) and MPK6, two environmentally responsive mitogen-activated protein kinases (MAPKs), and their upstream MAPK kinases, MKK4 and MKK5, are key regulators of stomatal development and patterning. Loss of function of MKK4/MKK5 or MPK3/MPK6 disrupts the coordinated cell fate specification of stomata versus pavement cells, resulting in the formation of clustered stomata. Conversely, activation of MKK4/MKK5-MPK3/MPK6 causes the suppression of asymmetric cell divisions and stomatal cell fate specification, resulting in a lack of stomatal differentiation. We further establish that the MKK4/MKK5-MPK3/MPK6 module is downstream of YODA, a MAPKKK. The establishment of a complete MAPK signaling cascade as a key regulator of stomatal development and patterning advances our understanding of the regulatory mechanisms of intercellular signaling events that coordinate cell fate specification during stomatal development.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The structure has been determined by electron cryomicroscopy of the adenosine triphosphate (ATP) synthase from
This analysis confirms features in a prior description of the structure of the enzyme, ...but it also describes other highly significant attributes not recognized before that are crucial for understanding the mechanism and regulation of the mycobacterial enzyme. First, we resolved not only the three main states in the catalytic cycle described before but also eight substates that portray structural and mechanistic changes occurring during a 360° catalytic cycle. Second, a mechanism of auto-inhibition of ATP hydrolysis involves not only the engagement of the C-terminal region of an α-subunit in a loop in the γ-subunit, as proposed before, but also a "fail-safe" mechanism involving the b'-subunit in the peripheral stalk that enhances engagement. A third unreported characteristic is that the fused bδ-subunit contains a duplicated domain in its N-terminal region where the two copies of the domain participate in similar modes of attachment of the two of three N-terminal regions of the α-subunits. The auto-inhibitory plus the associated "fail-safe" mechanisms and the modes of attachment of the α-subunits provide targets for development of innovative antitubercular drugs. The structure also provides support for an observation made in the bovine ATP synthase that the transmembrane proton-motive force that provides the energy to drive the rotary mechanism is delivered directly and tangentially to the rotor via a Grotthuss water chain in a polar L-shaped tunnel.
Determination of the amount of reactive nitrogen (Nr) deposition in excess of the ecosystem critical load (CL) requires an estimate of total deposition. Because the CL exceedance is used to inform ...policy decisions, uncertainty in both the CL and the exceedance itself must be understood. In this paper we review the state of the science with respect to the sources of uncertainty in total Nr deposition budgets used for CL assessments in North America and put forth recommendations for research and monitoring to improve deposition measurements and models. In the absence of methods to rigorously quantify uncertainty in total Nr deposition, a simple weighted deposition uncertainty metric (WDUM) is introduced as a tool for scientists and decision makers to use in assessing CL exceedances. Maps of the WDUM applied to National Atmospheric Deposition Program (NADP) Total Deposition (TDep) estimates show greater uncertainty in areas of the U.S. where dry deposition makes a larger contribution to the deposition budget, particularly ammonia (NH3) in agricultural areas and oxidized nitrogen (NOx) in urban areas. Organic N deposition is an important source of uncertainty over much of the U.S. Our analysis illustrates how the WDUM can be used to assess spatial patterns of deposition uncertainty and inform actions to improve deposition budgets for CL assessments at the local scale.
Display omitted
•Aspects of uncertainty in North American Nr deposition budgets are reviewed.•A simple metric of uncertainty (WDUM) for total Nr deposition is introduced.•Maps of WDUM show more uncertainty in areas of the U.S. where dry deposition dominates.•Long-term sites for Nr flux measurements are needed to improve dry deposition models.•Heterogeneity of land use is an important source of uncertainty in downscaling modeled deposition.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abscission is the process by which plants shed unwanted organs, either as part of a natural developmental program or in response to environmental stimuli. Studies in Arabidopsis thaliana have ...elucidated a number of the genetic components that regulate abscission of floral organs, including a pair of related receptor-like protein kinases, HAESA and HAESA -like 2 ( HAE / HSL2 ) that regulate a MAP kinase cascade that is required for abscission. HAE is transcriptionally up-regulated in the floral abscission zone just before cell separation. Here, we identify AGAMOUS-like 15 (AGL15; a MADS-domain transcription factor) as a putative regulator of HAE expression. Overexpression of AGL15 results in decreased expression of HAE as well as a delayed abscission phenotype. Chromatin immunoprecipitation experiments indicate that AGL15 binds the HAE promoter in floral receptacles. AGL15 is then differentially phosphorylated through development in floral receptacles in a MITOGEN-ACTIVATED PROTEIN KINASE KINASE 4/5-dependent manner. MAP kinase phosphorylation of AGL15 is necessary for full HAE expression, thus completing a positive feedback loop controlling HAE expression. Together, the network components in this positive feedback loop constitute an emergent property that regulates the large dynamic range of gene expression (27-fold increase in HAE ) observed in flowers when the abscission program is initiated. This study helps define the mechanisms and regulatory networks involved in a receptor-mediated signaling pathway that controls floral organ abscission.
Significance Dramatic changes in gene expression occur in abscission zones immediately prior to abscission. This study helps explain the mechanisms and emergent properties of a regulatory network that controls abscission. Two important connections are made that help explain the observed dynamic range of abscission gene expression. First, it connects a MAP kinase cascade that positively regulates abscission to a MADS-domain transcription factor, AGAMOUS-like 15 (AGL15). Second, it connects AGL15 to the expression of a receptor kinase known to control abscission. All together, the findings define a positive feedback loop that provides exponential signal amplification that starts with a receptor, goes through a MAP kinase cascade and a transcription factor, and then returns to the receptor.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Neuroplasticity is a robust mechanism by which the central nervous system attempts to adapt to a structural or chemical disruption of functional connections between neurons. Mechanical damage from ...spinal cord injury potentiates via neuroinflammation and can cause aberrant changes in neural circuitry known as maladaptive plasticity. Together, these alterations greatly diminish function and quality of life. This review discusses contemporary efforts to harness neuroplasticity through rehabilitation and neuromodulation to restore function with a focus on motor recovery following cervical spinal cord injury. Background information on the general mechanisms of plasticity and long-term potentiation of the nervous system, most well studied in the learning and memory fields, will be reviewed. Spontaneous plasticity of the nervous system, both maladaptive and during natural recovery following spinal cord injury is outlined to provide a baseline from which rehabilitation builds. Previous research has focused on the impact of descending motor commands in driving spinal plasticity. However, this review focuses on the influence of physical therapy and primary afferent input and interneuron modulation in driving plasticity within the spinal cord. Finally, future directions into previously untargeted primary afferent populations are presented.
Spatiotemporal-specific cell proliferation and cell differentiation are critical to the formation of normal tissues, organs, and organisms. The highly coordinated cell differentiation and ...proliferation events illustrate the importance of cell-cell communication during growth and development. In Arabidopsis thaliana, ERECTA (ER), a receptor-like protein kinase, plays important roles in promoting localized cell proliferation, which determines inflorescence architecture, organ shape, and size. However, the downstream signaling components remain unidentified. Here, we report a mitogen-activated protein kinase (MAPK; or MPK) cascade that functions downstream of ER in regulating localized cell proliferation. Similar to an er mutant, loss of function of MPK3/MPK6 or their upstream MAPK kinases (MAPKKs; or MKKs), MKK4/MKK5, resulted in shortened pedicels and clustered inflorescences. Epistasis analysis demonstrated that the gain of function of MKK4 and MKK5 transgenes could rescue the loss-of-function er mutant phenotype at both morphological and cellular levels, suggesting that the MPK3/MPK6 cascade functions downstream of the ER receptor. Furthermore, YODA (YDA), a MAPKK kinase, was shown to be upstream of MKK4/MKK5 and downstream of ER in regulating inflorescence architecture based on both gain-and loss-of-function data. Taken together, these results suggest that the YDA-MKK4/MKK5-MPK3/MPK6 cascade functions downstream of the ER receptor in regulating localized cell proliferation, which further shapes the morphology of plant organs.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Display omitted
•Shedding (abscission) along with growth determine a plant’s shape.•Similarities between abscission and dehiscence predict cell separation regulation.•Connections between abscission ...and linked processes clarify abscission.•PAD4 links abscission to senescence, pathogen defense, and drought tolerance.•A set of predictive rules regulating cell separation is presented.
This review focuses on relationships between the abscission process (organ shedding) and other related processes like shattering, senescence, pathogen defense, and drought stress with emphasis on how the relationships might be exploited to advance their respective fields. Shared molecular components provide a means for cross-talk between processes as well as a means for knowledge transfer between fields. The review briefly covers how fundamental abscission molecular mechanisms can be used for crop improvement. We cover seed abscission and shattering in rice, cereals, and beans as well as abscission in Arabidopsis and tomato. The review provides a set of five guidelines that can be used to direct future cell separation research. Finally, we give our perspective on methods and technologies that are likely to advance the abscission field.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Researchers and managers need effective tools for monitoring the use of forages by large herbivores. Since 2000, the number of herbivore diet studies has nearly doubled. In this review, we determine ...trends in the field; assess the utility of key techniques against five criteria (cost, accuracy and precision, resolution, utility for long-term monitoring programs, and appropriateness for browsers and grazers); and make recommendations to give managers appropriate tools. Three techniques stand out: microhistology, near infrared reflectance spectroscopy, and deoxyribonucleic acid (DNA) barcoding. Microhistology has a long history of use in rangelands and is often considered the gold standard for understanding diet composition, albeit at a high cost of labor. Near infrared reflectance spectroscopy can resolve the presence of target groups or species more quickly than microhistology, especially for grazers. DNA barcoding provides the greatest resolution of dietary items with less quantitative certainty than microhistology. The costs associated with DNA barcoding come primarily from technology and sequencing, while in microhistology they are associated with labor. Therefore, an improved, streamlined microhistology method could provide rangeland managers a rapid and cost-effective method for diet monitoring. Ultimately, the complex challenges facing rangeland managers today may require the use of more than one method to achieve acceptable resolution within actionable time frames.
PDF
