Using phytohormones and genotype selection to enhance biological nitrogen fixation in soybean

Soybean is the most important plant-based protein source and may be vital to sustainable agricultural intensification, required to support an ever-growing global population. Soybean, however, has a high nitrogen (N) demand which often limits yield. Biological nitrogen fixation (BNF), through symbiosis with rhizobia, is a natural process through which legumes can derive much of their N requirement, with many environmental benefits over chemical fertiliser application. Enhancement of BNF therefore offers an opportunity to sustainably increase yield. Nodules are root organs that form following legume perception of nod factors (NF) produced by compatible rhizobia species, leading to expression of NF response genes, including ENOD40. They are the sites of BNF, providing a highly controlled optimal environment for rhizobia to fix N. Primarily, work on symbiosis has focused on the signalling events that coordinate nodule initiation and development, with a key role of phytohormones tightly controlling this process. However, the effect of varying nodule morphologies on BNF capacity is little studied. This thesis uses two approaches, genotypic variation and phytohormone application, to enhance BNF and seeks to understand if differences in nodule traits (such as size, number or distribution) can explain differences in BNF. To better quantify nodule traits, a novel image analysis protocol was developed. To determine whether genotypic variation in nodule traits could explain differences in BNF capacity, six soybean genotypes with contrasting BNF capacities (based on previous literature) were studied. Although BNF and nodule traits varied between genotypes by up to 60%, there was no simple relationship between nodule formation and BNF as hypothesised. Instead, both genotype and growth stage interacted to affect BNF capacity, with different nodule traits influencing BNF to different extents across the soybean genotypes when measured at different stages. Nodule traits (nodule area or diameter) derived from novel image analysis techniques were better correlated with BNF than traditional assessment methods (nodule number or weight). To establish if phytohormone application could enhance BNF, three positive regulators (cytokinin, auxin and gibberellic acid) were applied at various concentrations via different application methods (seed coat, seed soak, root application and foliar spray). Of the phytohormones tested, only cytokinin (kinetin) gave promising results and was most effective when applied as a seed soak treatment (10-9 mol L-1). This treatment increased total nodule area (32%), doubling BNF. Interestingly, cytokinin treatments led to the nodules being more tightly clustered near the root crown (81% decrease in distance from root crown) suggesting that early nodule development was promoted. Indeed, cytokinin seed treatment increased the expression of ENOD40 by 52% after 72 hours. This suggests that cytokinin seed soaking primes the seeds by promoting the symbiotic pathway. As both genotype and cytokinin application changed nodule development and BNF in controlled environments, their agronomic potential was assessed in field trials in Argentina with early and conventional sowing dates. Low root zone temperature is a key limiting factor of nodule formation but is little studied despite growing interest in European grown soybean and early sowing dates elsewhere, where crops often experience cool growing conditions. Cytokinin treatment had limited positive effects on BNF but did not increase yield or total N uptake. Genotypic differences in yield were not explained by overall BNF across the growth period and were better associated with differences in soil N uptake, with 21% increase in higher yielding DM50I17. Interestingly, DM50I17 showed increased early nodule development (18% increase in nodule number) and correspondingly greater (52%) early BNF which might have improved yield through greater canopy N accumulation (9%), available for remobilisation. These field trials indicate BNF is an important N source during cold conditions, maintaining N supply leading to more consistent yield. In contrast to previous literature, soil N uptake was more sensitive to low root zone temperature than BNF. Taken together, this thesis is the first detailed examination of whether nodule traits affect BNF in soybean. It explored the potential of genotype selection and phytohormone application to enhance BNF by altering the number or size of nodules. Differences in nodule morphologies, particularly nodules with 4 mm diameter, influence BNF with increased nodule development positively correlated with BNF. Cytokinin seed priming enhances root ENOD40 expression and thus nodule formation and BNF. However, future work should further examine the effect of cytokinin priming on the symbiotic pathway to fully understand the mechanism(s) behind this treatment. Equally, greater understanding of changes in endogenous phytohormone concentration across genotypes and following cytokinin treatment may explain nodule variation seen in this study. Although genotype selection and phytohormone treatments did not always enhance BNF sufficiently to increase soybean yield, cytokinin application altered important nodule traits that may provide greater N (and yield) benefits in specific agronomic circumstances with limited N inputs

ReFOLD: a server for the refinement of 3D protein models guided by accurate quality estimates

ReFOLD is a novel hybrid refinement server with integrated high performance global and local Accuracy Self Estimates (ASEs). The server attempts to identify and to fix likely errors in user supplied 3D models of proteins via successive rounds of refinement. The server is unique in providing output for multiple alternative refined models in a way that allows users to quickly visualize the key residue locations, which are likely to have been improved. This is important, as global refinement of a full chain model may not always be possible, whereas local regions, or individual domains, can often be much improved. Thus, users may easily compare the specific regions of the alternative refined models in which they are most interested e.g. key interaction sites or domains. ReFOLD was used to generate hundreds of alternative refined models for the CASP12 experiment, boosting our group's performance in the main tertiary structure prediction category. Our successful refinement of initial server models combined with our built-in ASEs were instrumental to our second place ranking on Template Based Modeling (TBM) and Free Modeling (FM)/TBM targets. The ReFOLD server is freely available at: http://www.reading.ac.uk/bioinf/ReFOLD/

The role of women in United Kingdom farm businesses

The global empowerment of women has been, and remains to be, a continuing issue, especially within the workplace. The agribusiness industry is no exception, where continuation of gender bias and stereotypes positions women as under-represented. This qualitative study examines the self-identified roles of women in United Kingdom (UK) farm businesses through interviewing individual participants in the sector (n=8). The literature highlights four roles: which form a theoretical framework to structure the interviews. Findings show five emergent self-identification of role characterisations. Thus, while externally identified roles consider women’s status and contribution in a siloed job role structure, the multiplicity of roles that women undertake are much more nuanced and contiguous. The research contribution is an understanding of the variance and multiplicity of tasks undertaken which indicate the extensive work and contributory efforts that women instinctively provide to the farming business and the farm household structure. Findings contribute by establishing a new conceptualisation of the contributions of women to farm businesses informing rural policymakers, to consider the roles of women at farm household level rather than simply focussing on the gender characteristics of the principal farmer

‘It's the organization that is wrong’:Exploring disengagement from organizations through leadership development

This research explores the relationship between participation in leadership development programmes and disengagement from the employing organization. Based on repeated interviews with 10 managers participating in an open leadership development programme, our analysis shows that half of the participants reflected a sense of distancing themselves from how their organizations practiced leadership, and for some, an emotional disengagement with their home organization which we see as analogous to changes in social identity. We problematize the role of management and leadership development programmes with regard to the relationship between organizations and employees. A series of paradoxes are reflected in our critique of this relationship. The most prominent in terms of implications is that a successful management and leadership development programme – recognized by employees and employers – can generate dissatisfaction with the home organization as a consequence of the purpose of the programme: to increase confidence and enhanced agency. This paradox has significant implication to the leadership development industry and we explore these implications

The effect of underwater sounds on shark behaviour

The effect of sound on the behaviour of sharks has not been investigated since the 1970s. Sound is, however, an important sensory stimulus underwater, as it can spread in all directions quickly and propagate further than any other sensory cue. We used a baited underwater camera rig to record the behavioural responses of eight species of sharks (seven reef and coastal shark species and the white shark, Carcharodon carcharias) to the playback of two distinct sound stimuli in the wild: an orca call sequence and an artificially generated sound. When sounds were playing, reef and coastal sharks were less numerous in the area, were responsible for fewer interactions with the baited test rigs, and displayed less ‘inquisitive’ behaviour, compared to during silent control trials. White sharks spent less time around the baited camera rig when the artificial sound was presented, but showed no significant difference in behaviour in response to orca calls. The use of the presented acoustic stimuli alone is not an effective deterrent for C. carcharias. The behavioural response of reef sharks to sound raises concern about the effects of anthropogenic noise on these taxa

Genotype and cytokinin effects on soybean yield and biological nitrogen fixation across soil temperatures

High nitrogen (N) supply is required for high‐yielding soybean, but low soil temperatures in either early production systems or cool environments delay nodulation and limit biological nitrogen fixation (BNF). Because cytokinins are key signalling hormones in mediating nodule formation and our initial controlled environment experiment indicated that seed cytokinin treatment increased early BNF and total nodule area, it was used in field trials. Cytokinin was applied (seed or foliar) to two commercial soybean genotypes (DM50I17 and DM40R16) in field trials with early (September and early November) and conventional (late November) sowing dates in Argentina. In the field, DMR50I7 achieved consistent yields across sowing dates because increased BNF compensated for limited soil N uptake in early sowing dates, also leading to 25% higher nitrogen use efficiency (NUE). Surprisingly, soil N uptake was more cold‐sensitive than BNF with greater and prolonged N fixation in early sowing, perhaps through delayed nodulation, leading to improved N harvest index. Cytokinin seed treatment increased BNF (26%) in DM40R16 especially in early sowing dates. Although cytokinin improved cold tolerance of BNF, this was not explained by altered nodulation and did not increase yield. Here we show genetic differences in N supply in commercial soybean genotypes and the importance of BNF to maintain yield in early sown soybean

Search for light long-lived neutral particles that decay to collimated pairs of leptons or light hadrons in pp collisions at √s = 13 TeV with the ATLAS detector

A search for light long-lived neutral particles with masses in the O(MeV-GeV) range is presented. The analysis targets the production of long-lived dark photons in the decay of a Higgs boson produced via gluon-gluon fusion or in association with a W boson. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are selected in 139 fb−1 of √s = 13 TeV pp collision data collected by the ATLAS detector at the LHC. Background estimates for contributions from Standard Model processes and instrumental effects are extracted from data. The observed event yields are consistent with the expected background. Exclusion limits are reported on the production cross-section times branching fraction as a function of the mean proper decay length cτ of the dark photon, or as a function of the dark-photon mass and kinetic mixing parameter that quantifies the coupling between the Standard Model and potential hidden (dark) sectors. A Higgs boson branching fraction above 1% is excluded at 95% CL for a Higgs boson decaying into two dark photons for dark-photon mean proper decay lengths between 10 mm and 250 mm and dark photons with masses between 0.4 GeV and 2 GeV