Biology subjects

Lawrence, J. M.

Publications and source records attributed to Lawrence, J. M..

6 recordsLinked to original sources

bioRxiv2026

A conserved photosynthetic cytochrome enhances growth in fluctuating light

Having at least one of the small soluble electron carriers cytochrome c6 (c6) and plastocyanin is indispensable for photosynthesis. It was believed that c6 had been lost from plants until a ubiquitous and highly conserved homologue, now named cytochrome c6A (c6A), was found in Arabidopsis thaliana. In spite of an early suggestion that c6A functioned like c6 in the photosynthetic electron transport chain it was soon shown to be unable to do so despite the strong structural homology between the two proteins. The function of c6A, and why it is apparently universal in plants and green algae, therefore remained unknown. Here, we show that, in the green alga Chlamydomonas reinhardtii, c6A confers a growth advantage under fluctuating light and is crucial for maintaining the light harvesting balance between photosystems I and II in photomixotrophic conditions. We show that in the absence of c6A, the light harvesting balance shifts towards PSII, leading to a more reduced plastoquinone pool and increased photooxidative stress. This study provides insights into how photosynthetic organisms acclimatize to stressful light conditions, indicating that c6A is important for this adaptation. These findings provide a basis for further mechanistic studies on a hypothesized role for c6A in thiol-based redox regulation in the thylakoid lumen, with implications for photoprotection mechanisms such as state transitions.

plant biology↗

bioRxiv2025

Bioelectricity generation by Symbiodinium microadriaticum: a symbiont-forming photosynthetic dinoflagellate alga from coral reefs

Climate change is intensifying the phenomenon of coral bleaching, a highly ecologically damaging process that stems from the breakdown in the symbiotic relationship between photosynthetic dinoflagellate algae and Cnidaria (animals). Currently, little is understood about bleaching at the molecular level, since changes in metabolic and redox interactions between the dinoflagellate algae and Cnidaria are challenging to study. Here, we developed electrochemical approaches to measure extracellular electron transfer (EET, a type of bioelectricity) in Symbiodinium microadriaticum, a model species of symbiont-forming dinoflagellate algae, and show how this can be used to assess intracellular bioenergetic fluctuations within the alga. We show that EET is dependent on two major intracellular pathways - photosynthesis and respiration - and reveal that expelled electrons exit the cell via diffusible electron carriers. We confirm that EET activity can be affected by environmental stressors linked to coral bleaching, such as changes in temperature, pH and light intensity. Overall, this is a direct and non-invasive approach to provide quantitative measurements of S. microadriaticums bioenergetics and redox exchanges with the environment in stress conditions. This platform can aid our understanding of the coral-dinoflagellate symbiosis and the molecular mechanisms of bleaching.

microbiology↗

bioRxiv2025

Dissecting a biological electron transport network with electrochemistry

Photosynthetic membranes contain complex networks of redox proteins and molecules which direct electrons along various energy-to-chemical interconversion reactions important for sustaining life on Earth. Analysing and disentangling the mechanisms, regulation and interdependencies of these electron transfer pathways is extremely difficult, owing to the large number of interacting components in the native membrane environment. Whilst electrochemistry is well established for studying electron transfer in purified proteins, it has proven difficult to directly wire into proteins within their native membrane environments, and even harder to probe on a systems-level the electron transfer networks they are entangled within. Here, we show how photosynthetic membranes from cyanobacteria can be directly wired to electrodes to access their complex electron transfer networks. Measurements of native membranes with structured electrodes revealed distinctive electrochemical signatures, enabling analysis from the scale of individual proteins to entire biochemical pathways, as well as their interplay. This includes measurements of overlapping photosynthetic and respiratory pathways, the redox activities of membrane-bound quinones, along with validation using in operando spectroscopic measurements. Importantly, we further demonstrated direct extraction of electrons from native membrane-bound Photosystem I at -600 mV, which is [~]1 V more negative than from purified photosystems. This finding opens up opportunities for biotechnologies for solar electricity, fuel and chemical generation. We foresee this electrochemical method being adapted to analyze other photosynthetic and non-photosynthetic membranes, as well as aiding the development of new biocatalytic, biohybrid and biomimetic systems.

biochemistry↗

bioRxiv2021

A modular toolset for electrogenetics

Synthetic biology research and its industrial applications rely on the deterministic spatiotemporal control of gene expression. Recently, electrochemical control of gene expression has been demonstrated in electrogenetic systems (redox-responsive promoters used alongside redox inducers and an electrode), allowing for the direct integration of electronics with complex biological processes for a variety of new applications. However, the use of electrogenetic systems is limited by poor activity, tunability and standardisation. Here, we have developed a variety of genetic and electrochemical tools that facilitate the design and vastly improve the performance of electrogenetic systems. We developed a strong, unidirectional, redox-responsive promoter before deriving a mutant promoter library with a spectrum of strengths. We then constructed genetic circuits with these parts and demonstrated their activation by multiple classes of redox molecules. Finally, we demonstrated electrochemical activation of gene expression in aerobic conditions utilising a novel, modular bioelectrochemical device. This toolset provides researchers with all the elements needed to design and build optimised electrogenetic systems for specific applications.

synthetic biology↗

bioRxiv2021

A biophotoelectrochemical approach to unravelling the role of cyanobacterial cell structures in exoelectrogenesis

Photosynthetic microorganisms can export electrons outside their cells, a phenomenon called exoelectrogenesis, which can be harnessed for solar energy conversion. However, the route electrons take from thylakoid membranes to the cell exterior is not understood. Electrochemistry is a powerful analytical technique for studying electron transfer pathways. Here, we show how photoelectrochemistry can be used to compare electron flux from cyanobacterial cells of different growth stages, species and with the outer layers systematically removed. We show that the periplasmic space contributes significantly to the photocurrent profile complexity of whole cells, indicating that it gates electron transfer in exoelectrogenesis. We found that although components of the type IV pili machinery do not have a role in exoelectrogenesis, they contribute significantly to cell-electrode adherence. This study establishes that analytical photoelectrochemistry and molecular microbiology provide a powerful combination to study exoelectrogenesis, enabling future studies to answer biological questions and advance solar energy conversion applications.

biochemistry↗

bioRxiv2020

Fine-mapping, trans-ancestral and genomic analyses identify causal variants, cells, genes and drug targets for type 1 diabetes

We report the largest and most ancestrally diverse genetic study of type 1 diabetes (T1D) to date (61,427 participants), yielding 152 regions associated to false discovery rate < 0.01, including 36 regions associated to genome-wide significance for the first time. Credible sets of disease-associated variants are specifically enriched in immune cell accessible chromatin, particularly in CD4+ effector T cells. Colocalization with chromatin accessibility quantitative trait loci (QTL) in CD4+ T cells identified five regions where differences in T1D risk and chromatin accessibility are potentially driven by the same causal variant. Allele-specific chromatin accessibility further refined the set of putative causal variants with functional relevance in CD4+ T cells and integration of whole blood expression QTLs identified candidate T1D genes, providing high-yield targets for mechanistic follow-up. We highlight rs72938038 in BACH2 as a candidate causal T1D variant, where the T1D risk allele leads to decreased enhancer accessibility and BACH2 expression in T cells. Finally, we prioritise potential drug targets by integrating genetic evidence, functional genomic maps, and immune protein-protein interactions, identifying 12 genes implicated in T1D that have been targeted in clinical trials for autoimmune diseases. These findings provide an expanded genomic landscape for T1D, including proposed genetic regulatory mechanisms of T1D-associated variants and genetic support for therapeutic targets for immune intervention.

genetics↗