Posted on 3 October 2017
The scourge of swimming pool owners and freshwater ponds, green algae are able to siphon carbon dioxide from the air for use in photosynthesis, a key factor in the speed of their growth. Understanding this process may someday help researchers improve the growth rate of crops such as wheat and rice.
In two studies, published in the journal Cell, the team reported the first detailed inventory of the cellular machinery - located in an organelle known as the pyrenoid - that algae use to collect and concentrate carbon dioxide.
Furthermore, they found that the pyrenoid, long thought to be a solid structure, actually behaves like a liquid droplet that can dissolve into the surrounding cellular medium when the algal cells divide.
“We believe the liquid-like nature of the pyrenoid allows it to rapidly change from a condensed state to a dissolved state in response to a changing environment, further explaining why pyrenoid containing algae have become so efficient at photosynthesis”, said Dr Luke Mackinder, the lead author of one of the papers and a former postdoctoral researcher at the Carnegie Institution who now leads a team of researchers at the University of York.
Aquatic algae and a handful of other plants have developed carbon-concentrating mechanisms that boost the rate of photosynthesis - the process by which plants turn carbon dioxide and sunlight into sugars for growth. All plants use an enzyme called Rubisco to "fix" carbon dioxide into sugar that can be used or stored by the plant.
Algae have an advantage over many land plants because they cluster the Rubisco enzymes inside the pyrenoid, where the enzymes encounter high concentrations of carbon dioxide pumped in from the air. Having more carbon dioxide around allows the Rubisco enzymes to work faster.
The researchers identified the locations and functions of each protein, detailing the physical interactions between the proteins to create a pyrenoid "interactome".
The research revealed 89 new pyrenoid proteins, including ones that the researchers think usher carbon into the pyrenoid and others that are required for formation of the pyrenoid.
They also identified three previously unknown layers of the pyrenoid that surround the organelle like the layers of an onion.
"The information represents the best assessment yet of how this essential carbon-concentrating machinery is organized and suggests new avenues for exploring how it works," said Dr Mackinder.
“With additional studies, these findings may guide us in improving crop yields to feed an expanding global population”.
- Martin Jonikas (Project Leader, Princeton University)
- Elizabeth S Freeman Rosenzweig (Carnegie Institution/Stanford University)
- Ned Wingreen (Princeton University)
- Benjamin Engel (Max Planck Institute of Biochemistry)
"A spatial interactome reveals the protein organization of the algal CO2-concentrating mechanism" by Luke C M Mackinder, Chris Chen, Ryan D Leib, Weronika Patena, Sean R Blum, Matthew Rodman, Silvia Ramundo, Christopher M Adams and Martin C Jonikas, was published in the journal Cell.
The work was supported by the National Institutes of Health (grants S10RR027425 and 7DP2GM119137-02), the National Science Foundation (grants EF-1105617 and IOS-1359682), the Simons Foundation and Howard Hughes Medical Institute (grant 55108535), Princeton University, the University of York and the Carnegie Institution for Science.
"The eukaryotic CO2-concentrating organelle is liquid-like and exhibits dynamic reorganization" by Elizabeth S Freeman Rosenzweig, Bin Xu, Luis Kuhn Cuellar, Antonio Martinez-Sanchez, Miroslava Schaffer, Mike Strauss, Heather N Cartwright, Pierre Ronceray, Jürgen M Plitzko, Friedrich Förster, Ned S Wingreen, Benjamin D Engel, Luke C M Mackinder and Martin C Jonikas, was published in the journal Cell.
The study was supported by National Science Foundation (grants EF-1105617, IOS-1359682 and PHY-1305525), the Carnegie Institution for Science, the National Institutes of Health (grant T32GM007276), the Simons Foundation and Howard Hughes Medical Institute (grant #55108535), Princeton University, a CONACyT-DAAD Graduate Scholarship, a Fundación Séneca Postdoctoral Fellowship, an Alexander von Humboldt Foundation Postdoctoral Fellowship and Deutsche Forschungsgemeinschaft (grant FO 716/4-1).