Thermotolerant photosynthetic organisms endure worsening climate conditions such as increased temperatures and higher levels of CO2. These novel organisms maintain photosynthetic activity and growth under a wide temperature range (15-45oC) as opposed to their wild-type counterparts.
Thermotolerant organisms also exhibit higher transparency to light. Photosynthetic efficiency is maintained even though they produce and utilize less chlorophyll molecules; therefore less surface area is required for optimal cultivation. Furthermore, increased CO2 concentrations are preferable for thermotolerant organisms efficient photosynthesis.
The innovative solution discovered at The Weizmann Institute, involves replacement of 1-2 amino acid residues in a protein motif within the D1 protein subunit of Photosystem II (the protein complex responsible for the conversion of solar energy to a useful form of energy by photosynthesis). Such a solution has the potential to provide platforms for food production and sustainable energy in regions with harsh climate conditions that until today, were deemed unfit for cultivation.
- Bacterial platform to produce biomass or materials (e.g. nutraceuticals) in higher temperatures and higher CO2.
- Food and biofuel production: adaptation of crops to harsh climates.
- Enhanced Thermal stability and plasticity of the modified organisms to a much broader range than observed for the native organisms.
- Greater Light penetration (e.g. in ponds) without losing photosynthetic efficiency - thermotolerant organisms maintain efficient activity with less chlorophylls thus allowing greater transmission of light to deeper spaces.
- Thermotolerant organisms withstand high CO2 concentrations.
Professor Avigdor Scherz and his team focused on the sequences of the two major protein subunits D1 and D2 found in all purple bacteria PSII reaction centers. Two sites, D1-209 and D1-212, were found to show consistent changes between mesophilic, thermotolerant and thermophilic organisms including cyanobacteria, algae and green plants.
The sites are positioned in a GXXXG-like structural motif (where G denotes small residues such as Gly, Ala, Ser, Cys and Thr) typical of helix-helix interactions. The motif was found at the points of closest contact between the two major protein subunits, D1 and D2. It was shown that mutations in the amino acids within the identified GXXXG-like motif result in modification of the local flexibility of the reaction center and, consequently, in the induction of thermophilic behavior.