Biology subjects

Long, B. M.

Publications and source records attributed to Long, B. M..

4 recordsLinked to original sources

bioRxiv2026

Heterologous expression in E. coli reveals the bicarbonate transporter BicA2 drives carbon uptake in marine Prochlorococcus spp.

The widespread oceanic cyanobacterial Prochlorococcus genus is a major contributor to global carbon fixation, yet mechanisms enabling this lineage to elevate intracellular inorganic carbon as a substrate for photosynthesis remain unresolved. Cyanobacterial CO2 concentrating mechanisms typically rely on membrane-bound bicarbonate (HCO -) transporters SbtA1, SbtA2, BicA and BCT1, and CO2-to-HCO3- conversion uptake systems (CO2 pumps; NDH-I3 and NDH-I4), to elevate a cellular HCO3- pool for use by Rubisco-containing carboxysomes. Evidence suggests Prochlorococcus harbours carboxysomes with a low-CO2-specificity Rubisco, implying a functional CCM dependent on active HCO3- uptake. However, canonical CO2 pumps are absent, leaving distant HCO - transporter homologues, BicA2 and SbtA2, as prime candidates for HCO3- transport in this group. Yet these have not been functionally characterised. Here we demonstrate that BicA2 from P. marinus CCMP1375 mediates Na+-dependent HCO3- uptake in E. coli, while BicA2 from P. marinus CCMP1986 is inactive in its native form but acquired transport function through a single amino acid substitution during adaptive laboratory evolution. These findings confirm BicA2 as a low-affinity, Na+-dependent bicarbonate transporter with variable flux, revealing a previously uncharacterized CCM component in Prochlorococcus. This mechanistic insight reshapes our understanding of carbon acquisition strategies in the most abundant photosynthetic organism on Earth and highlights evolutionary plasticity in transporter function with implications for global biogeochemical cycles. HighlightThis study provides the first mechanistic evidence of bicarbonate transport in Prochlorococcus, revealing functional and evolutionary flexibility in its CO2-concentrating mechanism components and reshaping our understanding of carbon acquisition in the most abundant marine photoautotroph.

microbiology↗

bioRxiv2024

Engineering the cyanobacterial ATP-driven BCT1 bicarbonate transporter for functional targeting to C3 plant chloroplasts

The ATP-driven bicarbonate transporter 1 (BCT1), a four-component complex in the cyanobacterial CO2-concentrating mechanism, could enhance photosynthetic CO2 assimilation in plant chloroplasts. However, directing its subunits (CmpA, CmpB, CmpC and CmpD) to three chloroplast sub-compartments is highly complex. Investigating BCT1 integration into Nicotiana benthamiana chloroplasts revealed promising targeting strategies using transit peptides from the intermembrane space protein Tic22 for correct CmpA targeting, while the transit peptide of the chloroplastic ABCD2 transporter effectively targeted CmpB to the inner envelope membrane. CmpC and CmpD were targeted to the stroma by RecA and recruited to the inner envelope membrane by CmpB. Despite successful targeting, expression of this complex in CO2-dependent Escherichia coli failed to demonstrate bicarbonate uptake. We then used rational design and directed evolution to generate new BCT1 forms that were constitutively active. Several mutants were recovered, including a CmpCD fusion. Selected mutants were further characterized and stably expressed in Arabidopsis thaliana, but the transformed plants did not have higher carbon assimilation rates or decreased CO2 compensation points in mature leaves. While further analysis is required, this directed evolution and heterologous testing approach presents potential for iterative modification and assessment of CO2-concentrating mechanism components to improve plant photosynthesis. HighlightWe describe the directed evolution and rational design of a cyanobacterial four-component bicarbonate transporter and the localization of its subunits to various chloroplast sub-compartments for improving C3 plant photosynthesis.

plant biology↗

bioRxiv2023

Cyanobacterial α-carboxysome carbonic anhydrase is allosterically regulated by the Rubisco substrate RuBP

Cyanobacterial CO2 concentrating mechanisms (CCMs) sequester a globally significant proportion of carbon into the biosphere. Proteinaceous microcompartments, called carboxysomes, play a critical role in CCM function, housing two enzymes to enhance CO2 fixation: carbonic anhydrase (CA) and Rubisco. Despite its importance, our current understanding of the carboxysomal CAs found in [a]-cyanobacteria, CsoSCA, remains limited, particularly regarding the regulation of its activity. Here, we present the first structural and biochemical study of CsoSCA from the cyanobacterium Cyanobium PCC7001. Our results show that the Cyanobium CsoSCA is allosterically activated by the Rubisco substrate ribulose-1,5-bisphosphate (RuBP), and forms a hexameric trimer of dimers. Comprehensive phylogenetic and mutational analyses are consistent with this regulation appearing exclusively in cyanobacterial [a]-carboxysome CAs. These findings clarify the biologically relevant oligomeric state of -carboxysomal CAs and advance our understanding of the regulation of photosynthesis in this globally dominant lineage. One-Sentence SummaryThe carboxysomal carbonic anhydrase, CsoSCA, is allosterically activated by the Rubisco substrate RuBP, revealing a novel mechanism controlling key enzyme activity in cyanobacterial -carboxysomes.

molecular biology↗

bioRxiv2022

A cross-scale analysis to understand and quantify effects of photosynthetic enhancement on crop growth and yield

Photosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying effectively how the seasonal growth and yield dynamics of target crops might be affected over a wide range of environments is limited. Using a state-of-the-art cross-scale model we predicted crop-level impacts of a broad list of promising photosynthesis manipulation strategies for C3 wheat and C4 sorghum. The manipulation targets have varying effects on the enzyme-limited (Ac) and electron transport-limited (Aj) rates of photosynthesis. In the top decile of seasonal outcomes, yield gains with the list of manipulations were predicted to be modest, ranging between 0 and 8%, depending on the crop type and manipulation. To achieve the higher yield gains, large increases in both Ac and Aj are needed. This could likely be achieved by stacking Rubisco function and electron transport chain enhancements or installing a full CO2 concentrating system. However, photosynthetic enhancement influences the timing and severity of water and nitrogen stress on the crop, confounding yield outcomes. Strategies enhancing Ac alone offers more consistent but smaller yield gains across environments, Aj enhancement alone offers higher gains but is undesirable in less favourable environments. Understanding and quantifying complex cross-scale interactions between photosynthesis and crop yield will challenge and stimulate photosynthesis and crop research. Summary StatementLeaf-canopy-crop prediction using a state-of-the-art cross-scale model improves understanding of how photosynthetic manipulation alters wheat and sorghum growth and yield dynamics. This generates novel insights for quantifying impacts of photosynthetic enhancement on crop yield across environments.

plant biology↗