How Many Peas in a Pod? Legume Genes Responsible for Mutualistic Symbioses Underground

The nitrogen-fixing symbiosis between legume plants and Rhizobium bacteria is the most prominent plant–microbe endosymbiotic system and, together with mycorrhizal fungi, has critical importance in agriculture. The introduction of two model legume species, Lotus japonicus and Medicago truncatula, has enabled us to identify a number of host legume genes required for symbiosis. A total of 26 genes have so far been cloned from various symbiotic mutants of these model legumes, which are involved in recognition of rhizobial nodulation signals, early symbiotic signaling cascades, infection and nodulation processes, and regulation of nitrogen fixation. These accomplishments during the past decade provide important clues to understanding not only the molecular mechanisms underlying plant–microbe endosymbiotic associations but also the evolutionary aspects of nitrogen-fixing symbiosis between legume plants and Rhizobium bacteria. In this review we survey recent progress in molecular genetic studies using these model legumes

In Silico Insights into the Symbiotic Nitrogen Fixation in Sinorhizobium meliloti via Metabolic Reconstruction

BACKGROUND: Sinorhizobium meliloti is a soil bacterium, known for its capability to establish symbiotic nitrogen fixation (SNF) with leguminous plants such as alfalfa. S. meliloti 1021 is the most extensively studied strain to understand the mechanism of SNF and further to study the legume-microbe interaction. In order to provide insight into the metabolic characteristics underlying the SNF mechanism of S. meliloti 1021, there is an increasing demand to reconstruct a metabolic network for the stage of SNF in S. meliloti 1021. RESULTS: Through an iterative reconstruction process, a metabolic network during the stage of SNF in S. meliloti 1021 was presented, named as iHZ565, which accounts for 565 genes, 503 internal reactions, and 522 metabolites. Subjected to a novelly defined objective function, the in silico predicted flux distribution was highly consistent with the in vivo evidences reported previously, which proves the robustness of the model. Based on the model, refinement of genome annotation of S. meliloti 1021 was performed and 15 genes were re-annotated properly. There were 19.8% (112) of the 565 metabolic genes included in iHZ565 predicted to be essential for efficient SNF in bacteroids under the in silico microaerobic and nutrient sharing condition. CONCLUSIONS: As the first metabolic network during the stage of SNF in S. meliloti 1021, the manually curated model iHZ565 provides an overview of the major metabolic properties of the SNF bioprocess in S. meliloti 1021. The predicted SNF-required essential genes will facilitate understanding of the key functions in SNF and help identify key genes and design experiments for further validation. The model iHZ565 can be used as a knowledge-based framework for better understanding the symbiotic relationship between rhizobia and legumes, ultimately, uncovering the mechanism of nitrogen fixation in bacteroids and providing new strategies to efficiently improve biological nitrogen fixation

Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio

Effect of the determination method of the material parameters on the accuracy of forming limit analyses for 5000 series aluminum alloy

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Material modeling of 6016-O and 6016-T4 aluminum alloy sheets and application to hole expansion forming simulation

This study investigates the influence of heat treatment on the anisotropic plastic deformation behaviors of 6016-O and 6016-T4 aluminum alloy sheets. The two material samples were fabricated from the same lot and, therefore, have the same grain size and crystallographic texture. Biaxial tensile tests using both cruciform and tubular specimens are performed for many proportional stress paths in the first quadrant of stress space. The test results reveal that the degree of differential hardening (DH) is much larger in 6016-T4 than in 6016-O. It is shown that the work contour shape of 6016-O is controlled by crystallographic texture, whereas that of 6016-T4 presumably depends on GP-zones as well. From the biaxial stress test data, an appropriate yield function for each material is determined and employed in the finite element analysis of the hole expansion forming process. It was found that the Yld2000-2d yield function provides proper material representations of the plastic behavior of both material samples in the sense that it correctly predicts the fracture or localized neck locations, which occurs in the hole edge vicinity. For 6016-O, the thickness strain profile predicted with the Yld2000-2d yield function, which accounts for the DH of the material, is in better agreement with the experimental results than that obtained with the isotropic hardening model. For 6016-T4, the Yld2000-2d yield function with an exponent of 8 with the isotropic hardening assumption leads to a fair prediction of the experimental data. In order to enhance the accuracy of forming simulations for 6016-T4, it is necessary to develop a material model that is capable of reproducing the significant DH resulting from the GP-zones. ? 2016 Elsevier Ltd.1111Nsciescopu

Evaluation methods for drought tolerance of cowpeas

Cowpea (Vigna unguiculata [L.| Wulp.) is primarily grown in dry regions in the tropics, particularly in sub-Saharan Africa. Drought is important among several yield-reducing factors. Nine hundred cowpea accessions from the Genetic Resources Unit of IITA were evaluated for drought tolerance in a field during the dry season at the IITA Kano Station in northern Nigeria. Some of them were retested three times in greenhouses, once in Nigeria and twice in Japan, using seedlings planted in small pots with a soil moisture level of 3% wt. Tolerance scores to drought correlated highly significantly in repeated evaluations. Two of the accessions, TVu 11979 and TVu 14914, were always highly tolerant. Merits and demerits of the two methods, a field evaluation method and a pot evaluation method, are discussed

Numerical biaxial tensile test for sheet metal forming simulation of aluminium alloy sheets based on the homogenized crystal plasticity finite element method

The simulation of the stretch forming of A5182-O aluminum alloy sheet with a spherical punch is performed using the crystal plasticity (CP) finite element method based on the mathematical homogenization theory. In the simulation, the CP constitutive equations and their parameters calibrated by the numerical and experimental biaxial tensile tests with a cruciform specimen are used. The results demonstrate that the variation of the sheet thickness distribution simulated show a relatively good agreement with the experimental results.status: publishe

Agrophysiological constarints in intercropped cowpea: an analysis

Factors affecting cowpea growth in millet/cowpea intercropping were investigated in northern Nigeria. Ecological studies showed that cowpea received from 75% of incident light inside the intercropped canopy. In these light-limited conditions, cowpea varieties with a spreading growth habit can harvest more light than those with an erect growth habit by producing more leaves, as well as expanding their leaf area. However, the local spreading type has a low yield potential because of its low harvest index and inadequate root system (compared to the shoot system). Improvement of these two points in the local spreading variety without reducing its adaptability to shade ill produce a variety that is better adapted to intercropping. The effect of shade is most serious in the branch initiation stage, about 3—4 weeks after sowing, which inhibits branching significantly. Since leaves, which become source, as Well as pods, which become sink, grow on each branch and the main stem, the final grain yield in non branched cowpea is significantly reduced. Shade in the grain-filling stage also reduces final seed yield, but the effect is not as pronounced as shading during the branch-initiation stage. Root competition between cowpea and millet was greatest when cowpea was planted simultaneously with millet in the low rainfall environment. In alternate row intercropping With 75 cm row width, millet roots run horizontally and turn deep under the cowpea plants, while cowpea roots are distributed under the cowpea plant itself. This creates high root competition because roots of both species share the same root zone. In these conditions, if cowpea is planted simultaneously, millet roots are reduced in the deep zone. Consequently, early onset of drought reduces millet yield because millet does not have deep roots if planted simultaneously with cowpea

Investigation on Stress Relaxation Behavior of High-Strength Steel Sheets Based on Elasto-viscoplasticity

NUMISHEET 2018: 11th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes. 30 July to 3 August 2018, Tokyo, Japan.Stress relaxation is the phenomenon where stress of materials decreases under constant strain. In several previous studies, it was found that the stress relaxation makes uniform elongation larger, showing a possibility that this phenomenon can be utilized to increase the forming limit in combination with the flexible slide motion of a servo press. However, the stress relaxation phenomenon has not yet been sufficiently clarified. Authors previously investigated the stress relaxation behavior by applying several models where stress relaxation was described as an elasto-viscoplasticity behavior. However, a unified and quantitative description of strain rate sensitivity of flow stress and stress relaxation has not been sufficiently studied. In this study, we investigated the influence of strain, strain rate and relaxation time on stress relaxation phenomena of high strength steel sheets. Strain rate sensitivity of flow stress was modelled with m-power law. Stress relaxation behavior was also successfully approximated by a model derived from the m-power law with the parameters obtained by strain rate sensitivity tests, which suggests that both the strain rate sensitivity and the stress relaxation were based on a unified elasto-viscoplasticity. The mechanisms of stress relaxation was also discussed through numerical analyses

Nicotianamine synthase specifically expressed in root nodules of Lotus japonicus

In dicotyledonous plants, nicotianamine synthase (NAS) is thought to play a role in the intercellular transport of iron (Fe). Fe is an essential metal for nitrogen-fixing root nodules of legumes, prompting us to characterize the role of the NAS gene in detail. We previously compared gene-expression profiles in ineffective nodules formed on a Lotus japonicus Fix– mutant, sen1, with those in wild-type effective nodules, and showed that expression of an expressed sequence tag (EST) clone encoding an NAS (EC 2.5.1.43) homologue was repressed in the ineffective nodules. In the present study, two EST clones encoding NAS homologues were found in the EST database. We named them LjNAS1 and LjNAS2. Both were detected as single-copy genes in the L. japonicus genome, and conferred NAS activities in transformed Saccharomyces cerevisiae. LjNAS2 was expressed only in nodules, but LjNAS1 was expressed mainly in leaves, stems, and cotyledons. The level of LjNAS2 transcripts was highest in the nodules 24 days after inoculation with Mesorhizobium loti, and was localized in vascular bundles within the nodules. Expression of LjNAS2 was suppressed in ineffective nodules formed on Fix– mutants other than sen1. By contrast, nitrogenase activities of nodules were not influenced in LjNAS2-suppressed plants. We discuss the role of LjNAS2 from the aspect of Fe translocation in nodules