Biology subjects

Lawson, T.

Publications and source records attributed to Lawson, T..

16 recordsLinked to original sources

bioRxiv2026

Can small reductions in Rubisco content improve nitrogen use in wheat without negatively impacting biomass or grain yield?

In this study, the level of Rubisco protein was reduced in wheat using RNAi, to test the hypothesis that photosynthesis, growth, and grain yield could be maintained whilst improving nitrogen use efficiency. The RNAi Rubisco wheat plants, with a Rubisco activity of less than 70% of wild type (WT) plant levels, had reduced photosynthesis, reductions in leaf and stem biomass and decreased seed yield. Interestingly, in the wheat RNAi Rubisco lines that had a small (<30%) reduction in Rubisco activity, the seed number, total seed weight and harvest index were comparable to that of WT type plants. However, no improvement in photosynthetic nitrogen use efficiency (PNUE) was evident in any of the RNAi Rubisco lines. Notably, PNUE was lower than for WT wheat plants in the RNAi lines with more than a 30% reduction in Rubisco activity. This result was unexpected and caused by an accumulation of N in both the leaves and seeds. At present we do not have an explanation for this but one possible hypothesis is that it could be due to slower growth caused by a reduction in source strength in the RNAi plants, which in turn resulted in changes to carbon and nitrogen allocation. HighlightWheat RNAi plants with small reductions in the amount and activity of Rubisco had a similar biomass and total seed weight to that of untransformed controls but no improvement in nitrogen use efficiency was evident.

plant biology↗

bioRxiv2025

Extensive photophysiological variation in wild barley is linked to environmental origin

O_LIIntraspecific variation between crop wild relatives (CWRs) represents a source of untapped genetic diversity for crop improvement. At the same time, improving photosynthesis in crops has the potential to enhance yield. Thus, exploring variation for photophysiology within CWRs is an important, yet underexplored, research area. C_LIO_LIWe describe a common garden experiment where 320 wild barley accessions were grown across two seasons. A photophysiology phenotyping pipeline was employed to quantify >30 traits within this diversity panel. Population genetics, genome-wide association analyses (GWAS) and deep phenotyping were performed to address local adaptation hypotheses. C_LIO_LIHeritable variation was detected across this photophysiological spectrum, with genotype-by-environment (GxE) interactions being prevalent. Evidence for local adaptation was observed in the form of subpopulation differences, signals of selection, and allele frequency variation associated to markers identified via GWAS. Phenotyping of representative accessions across distinct water availabilities highlighted a role for stomatal conductance (gs) in adaptation to dry environments. C_LIO_LIWe identified substantial variation in key photosynthesis-associated traits in a CWR closely related to barley, an economically important crop species. Our results demonstrate that this variation is partially due to local adaptation, where plasticity in gs appears important for maintaining photosynthesis and biomass accumulation in water restricted conditions. C_LI

plant biology↗

bioRxiv2025

Guard cell photorespiration has a major impact on photosynthesis, growth and stomatal behavior in Arabidopsis

Photorespiration is a mandatory metabolic repair shunt of carbon fixation by the Calvin-Benson (CB) cycle in oxygenic phototrophs. Its extent depends mainly on the CO2/O2 ratio in chloroplasts, which is regulated via stomatal movements. However, despite comprehensive understanding on the role of photorespiration in mesophyll cells (MC), its role in guard cells (GC) is yet unknown. To analyze this issue, the key enzyme of photorespiration, glycine decarboxylase (GDC), was manipulated through overexpression and antisense suppression of the GDC H-protein gene. A positive correlation of GDC-H expression with growth, photosynthesis and carbohydrate biosynthesis was observed in the transgenic lines, demonstrating active photorespiration is involved in stomatal regulation. This view is supported by gas exchange measurements showing that optimized GC photorespiration improves plant acclimation towards conditions requiring a high photorespiratory capacity, including high light. Microscopic analysis revealed that altered photorespiratory flux also affected starch accumulation patterns in GC, eventually serving as the underlying mechanistic for altered stomatal behavior. Collectively, our data suggest that photorespiration is a key component of the regulatory circuit that coordinates stomatal movements with external and internal CO2 availability. Thus, manipulation of photorespiration in GC has the potential to engineer crops maintaining growth and photosynthesis under future climates. One-sentence summaryGuard-cell-specific manipulation of photorespiratory glycine decarboxylase reveals photorespiration is active in guard cells and makes a major contribution to stomatal metabolism and movements.

plant biology↗

bioRxiv2024

Simultaneous Overexpression of Three Enzymes of Chloroplast Metabolism Fails to Improve CO2 Assimilation or Biomass.

Ensuring an adequate food supply amidst a growing global population and climate change challenges, necessitates innovative strategies to enhance crop productivity. Previous studies have demonstrated that the simultaneous stimulation of different photosynthesis-related processes can increase the rate of photosynthetic carbon assimilation and plant biomass. This study evaluates an approach based on modelling aimed at simultaneously increasing photosynthetic and sink capacities in Nicotiana tabacum by overexpressing three key enzymes: Sedoheptulose-1,7-bisphosphatase (SBPase), Fructose-1,6-bisphosphate aldolase (FBP Aldolase), and ADP-glucose pyrophosphorylase (AGPase). Our results showed that this strategy does not significantly improve growth or carbon assimilation in Nicotiana tabacum under the tested conditions. This suggests that while the model informing our work offers a valuable framework, its application may require adjustments based on species and environmental conditions. Future research should explore these genetic modifications in species with larger sink capacities and under a range of growth conditions to fully realize the potential of photosynthetic optimization.

plant biology↗

bioRxiv2024

Engineering Rubisco Condensation in Chloroplasts to Manipulate Plant Photosynthesis

Although Rubisco is the most abundant enzyme globally, it is inefficient for carbon fixation because of its low turnover rate and limited ability to distinguish CO2 and O2, especially under high O2 conditions. To address these limitations, phytoplankton, including cyanobacteria and algae, have evolved CO2-concentrating mechanisms (CCM) that involve compartmentalizing Rubisco within specific structures, such as carboxysomes in cyanobacteria or pyrenoids in algae. Engineering plant chloroplasts to establish similar structures for compartmentalizing Rubisco has attracted increasing interest for improving photosynthesis and carbon assimilation in crop plants. Here, we present a method to effectively induce the condensation of endogenous Rubisco within tobacco (Nicotiana tabacum) chloroplasts by genetically fusing superfolder green fluorescent protein (sfGFP) to the tobacco Rubisco large subunit (RbcL). By leveraging the intrinsic oligomerization feature of sfGFP, we successfully created pyrenoid-like Rubisco condensates that display dynamic, liquid-like properties within chloroplasts without affecting Rubisco assembly and catalytic function. The transgenic tobacco plants demonstrated comparable autotrophic growth rates and full life cycles in ambient air relative to the wild-type plants. Our study offers a promising strategy for modulating endogenous Rubisco assembly and spatial organization in plant chloroplasts via phase separation, which provides the foundation for generating synthetic organelle-like structures for carbon fixation, such as carboxysomes and pyrenoids, to optimize photosynthetic efficiency.

plant biology↗

bioRxiv2024

Green Conversations: Harnessing Plant Communication to control growth light intensity.

Controlled Environment Agriculture (CEA) delivers increased crop production per unit land, contributing to resilient food systems amidst challenges of climate change, population growth and urbanization. However, high energy costs associated with lighting impose substantial barriers to the widespread adoption of CEA. While light is indispensable for growth, critically its utilization by crops throughout the photoperiod remains sub-optimal, reducing photosynthetic efficiency and wasting energy. Here we have developed and demonstrated a novel real-time plant bio-feedback system that enables crops to directly communicate optimal lighting requirements. Continuous non- invasive monitoring of photochemistry elicited decreased demand for light by basil at the end of the photoperiod. Our innovative approach increased yield by 10% and reduced energy consumption per unit fresh mass by 18%, delivering a 201gCO2 gFW-1 reduction in carbon footprint. Application of this technique at scale can revolutionise resource management of CEA, reinvigorating the productivity, profitability and sustainability of this food industry. Author ContributionsJS & TL: designed the experiments; JS, PD and PK: performed all physiology experiments and data acquisition and carried out data analyses. TL, JS, PD and TH wrote the MS and all authors commented on the MS. One-sentence summaryChlorophyll fluorescence measurements of photosynthetic efficiency can be used to control growth light intensity in real time, optimising crop performance and energy use.

plant biology↗

bioRxiv2024

DNA methylation contributes to plant acclimation to naturally fluctuating light

Plants in the natural environment experience continuous dynamic changes in light intensity. We have limited understanding on how plants adapt to such variable conditions. Here, we exposed Arabidopsis thaliana plants to naturally fluctuating light regimes alongside traditional square light regimes such as those often found in control environment growth chambers. The physiological response was highly consistent across experiments, indicating the involvement of an epigenetic mechanism, leading us to investigated differences in DNA methylation. Our results identified a large number of alterations in DNA methylation patterns between fluctuating light acclimated plants, and square light acclimated plants, demonstrating natural fluctuations in light impacts the plant epigenetic mechanisms. Most importantly, there are more differences in DNA methylation patterns between different light pattern regimes than between different light intensities. These differences in DNA methylation were accompanied by significant changes in gene expression, some of which correlated with altered DNA methylation. Interestingly, several transposable elements which displayed differential methylation were found to be differentially expressed between light regimes. Our data suggests DNA methylation plays a role in acclimation to natural light which may directly regulate gene expression and impact transposable element activation.

genomics↗

bioRxiv2023

The genetic basis of dynamic non-photochemical quenching and photosystem II efficiency in fluctuating light reveals novel molecular targets for maize (Zea mays) improvement

Maize (Zea mays L.) is a major global crop species which uses C4 photosynthesis. Although C4 is typically considered to be more efficient than C3 photosynthesis, especially under warmer and drier conditions, there is substantial evidence that its efficiency can still be further improved, which may benefit crop performance. Improving photosynthetic efficiency via targeted manipulation of non-photochemical quenching has focused on a limited set of genes that are known to be important determinants of the NPQ response in C3 plants. The C4 pathway may alter NPQ responses but only relatively few studies have explored genetic variation in NPQ kinetics in species that perform C4 photosynthesis. In addition, studies of NPQ responses in field-grown plants of either C3 or C4 species are especially limited. Here we apply high-definition phenotyping of NPQ responses and photosynthetic efficiency and quantitative trait locus (QTL) mapping using a field-grown maize Multi-parent Advanced Generation Inter-Cross (MAGIC) population, which combines the allelic diversity of eight contrasting inbred lines. We find substantial and consistent variation for dynamic NPQ and PSII efficiency for two subsequent field seasons. Further exploration of candidate genes within three major QTL regions identified a strong impact of allelic variation in expression of the minor PSII antenna protein CP24 (LHCB6) on a major QTL for NPQ and efficiency of PSII photochemistry on chromosome 10.

plant biology↗

bioRxiv2023

Leaf excision has minimal impact on photosynthetic parameters across crop functional types

Photosynthesis is increasingly becoming a recognised target for crop improvement. Phenotyping photosynthesis-related traits on field-grown material is a key bottleneck to progress here due to logistical barriers and short measurement days. Many studies attempt to overcome these challenges by phenotyping excised leaf material in the laboratory. To date there are no demonstrated examples of the representative nature of photosynthesis measurements performed on excised leaves relative to intact leaves in crops. Here, we tested whether standardised leaf excision on the day prior to phenotyping impacted a range of common photosynthesis-related traits across crop functional types using tomato (C3-dicot), barley (C3-monocot), and maize (C4-monocot). Potentially constraining aspects of leaf physiology that could be forecasted to impair photosynthesis in excised leaves, namely leaf water potential and abscisic acid accumulation, were not different between intact and excised leaves. We also observed non-significant differences in spectral reflectance and chlorophyll fluorescence traits between the treatments across the three species. However, we did observe some significant differences between gas exchange and photosynthetic capacity associated traits across all three species. This study represents a useful reference for those who perform measurements of this nature and the differences reported should be considered in associated experimental design and statistical analyses. HighlightAcross the main photosynthesis functional types (C3-dicot, C3-monot, and C4-monot) of major crops (tomato, barley, and maize), measurements of photosynthetic parameters demonstrate few, but important, differences when measured on excised relative to intact leaves.

plant biology↗

bioRxiv2020

Time series transcriptomics reveals a BBX32-directed control of dynamic acclimation to high light in mature Arabidopsis leaves

The photosynthetic capacity of mature leaves increases after several days exposure to constant or intermittent episodes of high light (HL) and is manifested primarily as changes in chloroplast physiology. This is termed dynamic acclimation but how it is initiated and controlled is unknown. From fully expanded Arabidopsis leaves, we determined HL-dependent changes in transcript abundance of 3844 genes in a 0-6h time-series transcriptomics experiment. It was hypothesised that among such genes were those that contribute to the initiation of dynamic acclimation. By focussing on HL differentially expressed transcription (co-)factor (TF) genes and applying dynamic statistical modelling to the temporal transcriptomics data, a gene regulatory network (GRN) of 47 predominantly photoreceptor-regulated (co)-TF genes was inferred. The most connected gene in this network was B-BOX DOMAIN CONTAINING PROTEIN32 (BBX32). Plants over-expressing BBX32 were strongly impaired in dynamic acclimation and displayed perturbed expression of genes involved in its initiation. These observations led to demonstrating that as well as regulation of dynamic acclimation by BBX32, CRYPTOCHROME1, LONG HYPOCOTYL5, CONSTITUTIVELY PHOTOMORPHOGENIC1 and SUPPRESSOR OF PHYA-105 are also important regulators of this process. Additionally, the BBX32-centric GRN provides a view of the transcriptional control of dynamic acclimation distinct from other photoreceptor-regulated processes, such as seedling photomorphogenesis.

plant biology↗

bioRxiv2020

SARS-CoV-2 RNA quantification using droplet digital RT-PCR

Quantitative viral load assays have transformed our understanding of - and ability to manage - viral diseases. They hold similar potential to advance COVID-19 control and prevention, but SARS-CoV-2 viral load tests are not yet widely available. SARS-CoV-2 molecular diagnostic tests, which typically employ real-time reverse transcriptase-polymerase chain reaction (RT-PCR), yield semi-quantitative results only. Reverse transcriptase droplet digital PCR (RT-ddPCR), a technology that partitions each reaction into 20,000 nanolitre-sized droplets prior to amplification, offers an attractive platform for SARS-CoV-2 RNA quantification. We evaluated eight primer/probe sets originally developed for real-time RT-PCR-based SARS-CoV-2 diagnostic tests for use in RT-ddPCR, and identified three (Charite-Berlin E-Sarbeco and Pasteur Institute IP2 and IP4) as the most efficient, precise and sensitive for RT-ddPCR-based SARS-CoV-2 RNA quantification. Analytical efficiency of the E-Sarbeco primer/probe set, for example, was ~83%, while assay precision, as measured by the coefficient of variation, was ~2% at 1000 input copies/reaction. Lower limits of quantification and detection for this primer/probe set were 18.6 and 4.4 input SARS-CoV-2 RNA copies/reaction, respectively. SARS-CoV-2 RNA viral loads in a convenience panel of 48 COVID-19-positive diagnostic specimens spanned a 6.2log10 range, confirming substantial viral load variation in vivo. We further calibrated RT-ddPCR-derived SARS-CoV-2 E gene copy numbers against cycle threshold (Ct) values from a commercial real-time RT-PCR diagnostic platform. The resulting log-linear relationship can be used to mathematically derive SARS-CoV-2 RNA copy numbers from Ct values, allowing the wealth of available diagnostic test data to be harnessed to address foundational questions in SARS-CoV-2 biology.

molecular biology↗

bioRxiv2020

The impact of stomatal kinetics on diurnal photosynthesis and water use efficiency under fluctuating light

Dynamic light conditions require continuous adjustments of stomatal aperture. As stomatal conductance (gs) kinetics are a magnitude slower than photosynthesis (A), they are hypothesized to be key to plant productivity and water use efficiency. Using step-changes in light intensity, we studied the diversity of light-induced gs kinetics in relation to stomatal anatomy in five banana genotypes (Musa spp.) and modelled the impact on A and intrinsic water use efficiency (iWUE). Banana generally exhibited a strong limitation of A by gs, indicating a priority for water saving. Significant genotypic differences in gs kinetics and gs-based limitations of A were observed. For two contrasting genotypes the impact of differential gs kinetics on A and iWUE was further investigated under realistic diurnally fluctuating light conditions and at whole-plant level. Genotype-specific stomatal kinetics observed at the leaf level were corroborated at whole-plant level, suggesting that despite differences in gs control at different locations in the leaf and across leaves, genotype-specific responses are still maintained. However, under diurnally fluctuating light conditions gs speediness had only a momentary impact on the diurnal iWUE and carbon gain. During the afternoon there was a setback in kinetics: the absolute gs and the gs responses to light were damped, strongly limiting A and the diurnal iWUE. We conclude that the impact of the differential gs kinetics on the limitation of A was dependent on the target light intensity, the magnitude of change, the gs prior to the intensity change and particularly the time of the day. One sentence summaryGenotype-specific stomatal rapidity is for the first time validated at whole-plant level, but under fluctuating light the impact of stomatal dynamics depends on other factors like the time of the day.

plant biology↗

bioRxiv2020

A biophysical and structural analysis of DNA binding by oligomeric hSSB1 (NABP2/OBFC2B)

The oxidative modification of DNA can result in the loss of genome integrity and must be repaired to maintain overall genomic stability. We have recently demonstrated that human single stranded DNA binding protein 1 (hSSB1/NABP2/OBFC2B) plays a crucial role in the removal of 8-oxo-7,8-dihydro- guanine (8-oxoG), the most common form of oxidative DNA damage. The ability of hSSB1 to form disulphide-bonded tetramers and higher oligomers in an oxidative environment is critical for this process. In this study, we have used nuclear magnetic resonance (NMR) spectroscopy and surface plasmon resonance (SPR) experiments to determine the molecular details of ssDNA binding by oligomeric hSSB1. We reveal that hSSB1 oligomers interact with single DNA strands containing damaged DNA bases; however, our data also show that oxidised bases are recognised in the same manner as undamaged DNA bases. We further demonstrate that oxidised hSSB1 interacts with ssDNA with a significantly higher affinity than its monomeric form confirming that oligomeric proteins such as tetramers can bind directly to ssDNA. NMR experiments provide evidence that oligomeric hSSB1 is able to bind longer ssDNA in both binding polarities using a distinct set of residues different to those of the related SSB from Escherichia coli.

biochemistry↗

bioRxiv2020

Simultaneous stimulation of RuBP regeneration and electron transport increases productivity and water use efficiency under field conditions

Previous studies have demonstrated that independent stimulation of either electron transport or RuBP regeneration can increase the rate of photosynthetic carbon assimilation and plant biomass. In this paper, we present evidence that a multi-gene approach to simultaneously manipulate these two processes provides a further stimulation of photosynthesis. We report on the introduction of the cyanobacterial bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase or overexpression of the plant enzyme sedoheptulose-1,7-bisphosphatase, together with expression of the red algal protein cytochrome c6, and show that a further increase in biomass accumulation under both glasshouse and field conditions can be achieved. Furthermore, we provide evidence that the simultaneous stimulation of electron transport and RuBP regeneration can lead to enhanced intrinsic water use efficiency under field conditions. One sentence summarySimultaneous stimulation of RuBP regeneration and electron transport results in improvements in biomass yield in glasshouse and field grown tobacco.

plant biology↗

bioRxiv2019

Photosynthesis and crop productivity is enhanced by glucose-functionalized fluorescent carbon dots

From global food security to textile production and biofuels, the demands currently made on plant photosynthetic productivity will continue to increase. Enhancing photosynthesis using designer, green and sustainable materials offers an attractive alternative to current genetic-based strategies and promising work with nanomaterials has recently started to emerge. Here we describe in planta use of carbon-based nanoparticles produced by low-cost renewable routes that are bioavailable to mature plants. Uptake of these functionalised nanoparticles from the soil improves photosynthesis and also increases crop production. We show for the first time that glucose-functionalization enhances nanoparticle uptake, photoprotection and pigment production, unlocking enhanced yields. This is demonstrated in Triticum aestivum Apogee (dwarf bread wheat) and results in an 18% increase in grain yield. This establishes the viability of a functional nanomaterial to augment photosynthesis as a route to increased crop productivity.

plant biology↗

bioRxiv2017

Over-Expression Of The RieskeFeS Protein Increases Electron Transport Rates And Yield In Arabidopsis

In this study we have generated transgenic Arabidopsis plants over-expressing the Rieske FeS protein (PetC), a component of the cytochrome b6f (cyt b6f) complex. Increasing the levels of this protein, resulted in the concomitant increase in the levels of cyt f (PetA) and cyt b6 (PetB), core proteins of the cyt b6f complex. Interestingly, an increase in the levels of proteins in both the PSI and PSII complexes was also seen in the Rieske FeS ox plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, the overexpression of the Rieske FeS protein resulted in a substantial and significant impact on the quantum efficiency of PSI and PSII, electron transport, biomass and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity.\n\nOne-sentence summaryOver-expression of the Rieske FeS protein results in significant increases in the quantum efficiencies or PSI and PSII, increases in Amax and has the potential to increase crop productivity

plant biology↗