Investigating inorganic carbon transport in globally important algal lineages

Lead Research Organisation: University of York
Department Name: Biology

Abstract

Algae are responsible for up to 30% of all global photosynthesis, the process whereby light and CO2 are converted into O2 and chemical energy, in the form of sugars. This process provides energy for the bottom of the global food web, produces the O2 we breathe and plays an important role in removing the greenhouse gas CO2 from the atmosphere. Algae have evolved a mechanism to boost their photosynthesis making it very efficient, this mechanism is known as the CO2 concentrating mechanism (CCM). The CCM functions by taking up both CO2 and HCO3- from the environment to fuel photosynthesis. Algae take up HCO3- as well as the necessary CO2 because: (1) it can easily be converted to the CO2 needed for photosynthesis; (2) it is more readily available than CO2 in the aquatic environments algae live in; and (3) it doesn't leak out the cell like CO2 is prone to. The HCO3- is transported through the algal cell to a compartment called the thylakoid, which is found in the chloroplast and is where the photosynthetic process occurs. In the thylakoid the HCO3- is converted to CO2. The CO2 then is readily available for an enzyme called Rubisco which uses it to drive the photosynthesis process. Although we know HCO3- transport is very important in the CCM, until now we did not know how it travelled into the thylakoid to be converted to CO2. My research has recently identified a protein channel that enables HCO3- transport into the thylakoid in a species of algae called Chlamydomonas reinhardtii. I have also identified similar protein channels in other environmentally important groups of algae. I hypothesise that these similar protein channels may be a shared mechanism of HCO3- transport across algal groups. The Fellowship research I have proposed will extensively investigate these potential HCO3- channels in different algal groups to fully understand their function. Many algae have a CCM, but we know there are differences in the specific mechanism between different groups. Therefore, it is important to explore CCM components, like HCO3- channels, in different groups to be able to inform the research community accurately on the shared components in the algal CCM. This research is important because it strengthens our understanding of a process responsible for approximately a third of all global photosynthesis, influencing all life on Earth. The data generated in this project also helps researchers I collaborate with closely who are attempting to engineer a CCM into crop plants. If the CCM is successfully inserted into crop plants, it has been modelled to significantly increase photosynthetic efficiency and therefore increase crop yields by up to 60%. This yield increase could directly alleviate issues surrounding global food supply which have been increasing as a result of population increase and climate change.

Technical Summary

Photosynthesis is fundamental to life on Earth. Up to 30% of global photosynthesis is conducted by algae, a diverse group of eukaryotes living in aquatic environments. Numerous lineages of algae have evolved CO2 concentrating mechanisms (CCMs) to enhance the efficiency of their photosynthesis. A crucial component of the CCM is HCO3- transport through the cell, but the protein mediated pathway the HCO3- takes remains unresolved. I have recently identified a bestrophin-like protein channel (BST1) in the green algae Chlamydomonas reinhardtii (hereafter Chlamydomonas). BST1 has been shown to localise to the thylakoid membrane; is involved in the CCM; and has been shown to be specifically permeable to HCO3- anions using a Xenopus expression system. The data conclude BST1 enables HCO3- transport across the thylakoid membrane in Chlamydomonas. I have subsequently identified BST1 homologues in broad algal lineages and hypothesise this may be a shared mechanism of inorganic carbon (Ci) transport. Although Chlamydomonas is the most well characterised algal CCM, the majority of algal primary productivity is conducted by marine algal outside the green lineage. Therefore, this project will characterise the bestrophin-like proteins in Chlamydomonas and wider algal lineages, including diatoms and coccolithophores, to fully understand potential shared components of HCO3- transport through the algal CCM and the environmental relevance of these channels. To study these proteins I will (1) conduct extensive bioinformatics analysis; (2) investigate the protein structure using biochemical and cryoEM approaches; (3) use a range of molecular biology techniques including fluorescent tagging for localisation studies and quantitative gene expression analysis to investigate the regulation of these proteins in response to CCM induction; (4) generation of CRISPR knock-out mutants and their characterisation; and (5) functional screening through a heterologous expression system.

Publications

10 25 50
 
Description Collaboration with Cornelia Spetea Wiklund's lab, Gothenburg, Sweden 
Organisation University of Gothenburg
Country Sweden 
Sector Academic/University 
PI Contribution Providing expertise, generating plasmids and algal transformation experiments.
Collaborator Contribution Providing expertise and conducting photosynthetic phenotyping experiments.
Impact Two publications, one lead by CEW and one lead by the PDRA in CSW's lab will be submitted in 2023.
Start Year 2022
 
Description Collaboration with Gilles Peltier's Lab, CEA Cadrache, France 
Organisation Alternative Energies and Atomic Energy Commission (CEA)
Country France 
Sector Public 
PI Contribution Providing mutant lines and antibodies generated by CEW.
Collaborator Contribution Gilles Peltier is providing expertise and conducting MIMs experiments that are aiding my fellowship project.
Impact One paper including Gilles' data is about the be submitted, a second is anticipated later this year.
Start Year 2022
 
Description Case Study at the Physics of Life ECR grant writing and career development bootcamp 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Recorded presentation and case study at the Physics of Life ECR grant writing and career development bootcamp.
Year(s) Of Engagement Activity 2022
 
Description Conference Presentation at CCM10 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Competitively selected speaker at CCM10 in Princeton, NJ, USA. CCM10 is the conference for my research field and I received positive feedback for my work and some ideas going forward. I have also been asked to be on the committee for the next meeting CCM11 to be held in York, UK.
Year(s) Of Engagement Activity 2022
URL https://www.princeton.edu/events/2022/ccm10-meeting-gathering-space-0
 
Description Fellowships workshop speaker 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Fellowships workshop at the University of York 2022. I was an invited speaker and I presented on my position as a BBSRC Discovery Fellow and the application process. I have been invited to speak again for 2023.
Year(s) Of Engagement Activity 2022
 
Description School Visit (Caversham, Reading) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Invited speaker to Queen Anne's School Caversham to talk at the Lower Sixth Enrichment Symposium. I presneted one of four talks by academics to 100 + pupils and a selection of staff. I have been invited back for 2024.
Year(s) Of Engagement Activity 2023