About This Project

Enhancing photosynthesis can help mitigate greenhouse gases, but plants and algae use only visible light (400-700 nm), leaving much of the light spectrum untapped. This project introduces chlorophyll f, a pigment that absorbs far-red light (700-800 nm), into a plant, enabling greater photosynthetic efficiency that boosts biomass growth and CO2 sequestration. This bioengineering approach supports the Homeworld Collective’s mission to develop synthetic biology solutions for CO2 removal.

Ask the Scientists

Motivating Factor

Photosynthesis forms the basis for higher life on Earth and is the primary mechanism for global carbon sequestration, converting atmospheric CO₂ into biomass. Photosynthetic efficiency, however, is limited by the range of light wavelengths that photosynthetic organisms can use for energy conversion [1], thus limiting natural carbon sequestration. Most photosynthetic organisms use visible light (400-700 nm) which accounts for ~50% of solar energy. Therefore, a significant portion of available light remains unused, especially when visible light is attenuated due to shading [2]. This reduces the potential for carbon sequestration and biomass production, which in turn constrains efforts to address rising CO₂ levels and global energy demands. Expanding and tuning the spectral range of light absorption in photosynthetic organisms could significantly enhance photosynthetic efficiency [3, 4], contributing to scalable greenhouse gas removal strategies.

Specific Bottleneck

At the heart of photosynthesis are two protein complexes that harvest light and convert it to chemical energy, called photosystems I and II (PSI and PSII) [5]. A key bottleneck in improving photosynthetic efficiency is the competition between the two for the same range of visible light photons [4]. This competition results in inefficient energy utilization and limits overall photosynthetic output. In plant canopies where lower levels receive minimal light, this inefficiency is exacerbated. Recent discoveries have shown that some photosynthetic microorganisms, called cyanobacteria, have evolved mechanisms to overcome this limitation by altering their photosystems to additionally use light between 700 and 800 nm [6], called far-red light, but this adaptation is not observed in any plants. Our challenge lies in engineering plants to exhibit properties similar to those allowing for far-red light absorption in the unique cyanobacteria, which would improve overall photosynthesis.

Actionable Goals

To address this bottleneck, we aim to engineer plants with expanded light absorbance capabilities by leveraging known known far-red light photoacclimation mechanisms in cyanobacteria. This involves:

• Introducing and optimizing the biosynthetic pathway for a far-red light-absorbing chlorophyll (chlorophyll f) into a plant.
• Testing whether and where chlorophyll f binds nonspecifically to the photosystems and if it leads to far-red light absorption.
• Engineering the plant photosystems to bind chlorophyll f at specific locations that allows for photochemistry.
• Evaluating the impact of these modifications on photosynthetic efficiency and biomass yield in controlled conditions.

By achieving these goals, we can significantly enhance the capacity of plants to capture and convert light energy, providing a viable pathway for improving biological CO₂ sequestration.