ORCID Profile
0000-0002-7255-872X
Current Organisation
The University of Edinburgh
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Publisher: Oxford University Press (OUP)
Date: 06-07-2020
DOI: 10.1093/JXB/ERAA316
Abstract: The primary CO2-fixing enzyme Rubisco limits the productivity of plants. The small subunit of Rubisco (SSU) can influence overall Rubisco levels and catalytic efficiency, and is now receiving increasing attention as a potential engineering target to improve the performance of Rubisco. However, SSUs are encoded by a family of nuclear rbcS genes in plants, which makes them challenging to engineer and study. Here we have used CRISPR/Cas9 [clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9] and T-DNA insertion lines to generate a suite of single and multiple gene knockout mutants for the four members of the rbcS family in Arabidopsis, including two novel mutants 2b3b and 1a2b3b. 1a2b3b contained very low levels of Rubisco (~3% relative to the wild-type) and is the first ex le of a mutant with a homogenous Rubisco pool consisting of a single SSU isoform (1B). Growth under near-outdoor levels of light demonstrated Rubisco-limited growth phenotypes for several SSU mutants and the importance of the 1A and 3B isoforms. We also identified 1a1b as a likely lethal mutation, suggesting a key contributory role for the least expressed 1B isoform during early development. The successful use of CRISPR/Cas here suggests that this is a viable approach for exploring the functional roles of SSU isoforms in plants.
Publisher: Cold Spring Harbor Laboratory
Date: 06-08-2023
DOI: 10.1101/2023.08.04.552009
Abstract: Synechococcus sp. PCC 11901 (PCC 11901) is a fast-growing marine cyanobacterial strain that has a capacity for sustained biomass accumulation to very high cell densities, comparable to that achieved by commercially relevant heterotrophic organisms. However, genetic tools to engineer PCC 11901 for biotechnology applications are limited. Here we describe a suite of tools based on the CyanoGate MoClo system to unlock the engineering potential of PCC 11901. First, we characterised neutral sites suitable for stable genomic integration that do not affect growth even at high cell densities. Second, we tested a suite of constitutive promoters, terminators, and inducible promoters including a 2,4-diacetylphloroglucinol (DAPG)-inducible PhlF repressor system, which has not previously been demonstrated in cyanobacteria and showed tight regulation and a 228-fold dynamic range of induction. Lastly, we developed a DAPG-inducible dCas9-based CRISPR interference (CRISPRi) system and a modular method to generate markerless mutants using CRISPR-Cas12a. Based on our findings, PCC 11901 is highly responsive to CRISPRi-based repression and showed high efficiencies for single insertion (31-81%) and multiplex double insertion (25%) genome editing with Cas12a. We envision that these tools will lay the foundations for the adoption of PCC 11901 as a robust model strain for engineering biology and green biotechnology. Genetic parts were characterised in Synechococcus sp. PCC 11901, including a tightly regulated inducible promoter system, efficient CRISPRi and a novel markerless Cas12a genome editing approach.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3EE40491A
Publisher: Oxford University Press (OUP)
Date: 24-04-2017
DOI: 10.1093/JXB/ERX133
Abstract: Growth and productivity in important crop plants is limited by the inefficiencies of the C3 photosynthetic pathway. Introducing CO2-concentrating mechanisms (CCMs) into C3 plants could overcome these limitations and lead to increased yields. Many unicellular microautotrophs, such as cyanobacteria and green algae, possess highly efficient biophysical CCMs that increase CO2 concentrations around the primary carboxylase enzyme, Rubisco, to enhance CO2 assimilation rates. Algal and cyanobacterial CCMs utilize distinct molecular components, but share several functional commonalities. Here we outline the recent progress and current challenges of engineering biophysical CCMs into C3 plants. We review the predicted requirements for a functional biophysical CCM based on current knowledge of cyanobacterial and algal CCMs, the molecular engineering tools and research pipelines required to translate our theoretical knowledge into practice, and the current challenges to achieving these goals.
Publisher: MDPI AG
Date: 23-06-2022
DOI: 10.3390/BIOM12070872
Abstract: Synechococcus sp. PCC 11901 reportedly demonstrates the highest, most sustained growth of any known cyanobacterium under optimized conditions. Due to its recent discovery, our knowledge of its biology, including the factors underlying sustained, fast growth, is limited. Furthermore, tools specific for genetic manipulation of PCC 11901 are not established. Here, we demonstrate that PCC 11901 shows faster growth than other model cyanobacteria, including the fast-growing species Synechococcuselongatus UTEX 2973, under optimal growth conditions for UTEX 2973. Comparative genomics between PCC 11901 and Synechocystis sp. PCC 6803 reveal conservation of most metabolic pathways but PCC 11901 has a simplified electron transport chain and reduced light harvesting complex. This may underlie its superior light use, reduced photoinhibition, and higher photosynthetic and respiratory rates. To aid biotechnology applications, we developed a vitamin B12 auxotrophic mutant but were unable to generate unmarked knockouts using two negative selectable markers, suggesting that recombinase- or CRISPR-based approaches may be required for repeated genetic manipulation. Overall, this study establishes PCC 11901 as one of the most promising species currently available for cyanobacterial biotechnology and provides a useful set of bioinformatics tools and strains for advancing this field, in addition to insights into the factors underlying its fast growth phenotype.
Publisher: Wiley
Date: 13-01-2017
DOI: 10.1111/NPH.14414
Abstract: Introducing components of algal carbon concentrating mechanisms ( CCM s) into higher plant chloroplasts could increase photosynthetic productivity. A key component is the Rubisco‐containing pyrenoid that is needed to minimise CO 2 retro‐diffusion for CCM operating efficiency. Rubisco in Arabidopsis was re‐engineered to incorporate sequence elements that are thought to be essential for recruitment of Rubisco to the pyrenoid, namely the algal Rubisco small subunit ( SSU , encoded by rbcS ) or only the surface‐exposed algal SSU α‐helices. Leaves of Arabidopsis rbcs mutants expressing ‘pyrenoid‐competent’ chimeric Arabidopsis SSU s containing the SSU α‐helices from Chlamydomonas reinhardtii can form hybrid Rubisco complexes with catalytic properties similar to those of native Rubisco, suggesting that the α‐helices are catalytically neutral. The growth and photosynthetic performance of complemented Arabidopsis rbcs mutants producing near wild‐type levels of the hybrid Rubisco were similar to those of wild‐type controls. Arabidopsis rbcs mutants expressing a Chlamydomonas SSU differed from wild‐type plants with respect to Rubisco catalysis, photosynthesis and growth. This confirms a role for the SSU in influencing Rubisco catalytic properties.
Publisher: MDPI AG
Date: 26-05-2022
DOI: 10.20944/PREPRINTS202205.0362.V1
Abstract: Synechococcus sp. PCC 11901 reportedly demonstrates the highest, sustained growth of any known cyanobacterium under optimized conditions. Due to its recent discovery our knowledge of its biology, including the factors underlying sustained, fast growth, is limited. Furthermore, tools specific for genetic manipulation of PCC 11901 are not established. Here, we demonstrate that PCC 11901 shows faster growth than other model cyanobacteria, including the fast-growing species Synechococcus elongatus UTEX 2973, under optimal growth conditions for UTEX 2973. Comparative genomics between PCC 11901 and Synechocystis sp. PCC 6803 reveal conservation of most metabolic pathways but PCC 11901 has a simplified electron transport chain and reduced light-harvesting complex. This may underlie its superior light utilization, reduced photoinhibition and higher photosynthetic and respiratory rates. To aid biotechnology applications we developed a vitamin B12 auxotrophic mutant but were unable to generate unmarked knockouts using two negative selectable markers, suggesting that recombinase- or CRISPR-based approaches may be required for repeated genetic manipulation. Overall, this study establishes PCC 11901 as one of the most promising species currently available for cyanobacterial biotechnology and provides a useful set of bioinformatics tools and strains for advancing this field, in addition to insights into the factors underlying its fast growth phenotype.
Publisher: MDPI AG
Date: 29-09-2019
DOI: 10.3390/MICROORGANISMS7100409
Abstract: Recent advances in synthetic biology and an emerging algal biotechnology market have spurred a prolific increase in the availability of molecular tools for cyanobacterial research. Nevertheless, work to date has focused primarily on only a small subset of model species, which arguably limits fundamental discovery and applied research towards wider commercialisation. Here, we review the requirements for uptake of new strains, including several recently characterised fast-growing species and promising non-model species. Furthermore, we discuss the potential applications of new techniques available for transformation, genetic engineering and regulation, including an up-to-date appraisal of current Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR associated protein (CRISPR/Cas) and CRISPR interference (CRISPRi) research in cyanobacteria. We also provide an overview of several exciting molecular tools that could be ported to cyanobacteria for more advanced metabolic engineering approaches (e.g., genetic circuit design). Lastly, we introduce a forthcoming mutant library for the model species Synechocystis sp. PCC 6803 that promises to provide a further powerful resource for the cyanobacterial research community.
Publisher: Oxford University Press (OUP)
Date: 28-02-2019
DOI: 10.1104/PP.18.01401
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Alistair McCormick.