CBI, ORNL and CABBI researchers ID poplar tree gene that boosts photosynthesis

In Tennessee, a team of scientists with two Department of Energy Bioenergy Research Centers — the Center for Bioenergy Innovation, or CBI, at Oak Ridge National Laboratory and the Center for Advanced Bioenergy and Bioproducts Innovation, or CABBI, at the University of Illinois Urbana-Champaign — identified a gene in a poplar tree that enhances photosynthesis and can boost tree height by about 30% in the field and by as much as 200% in the greenhouse. 

The gene, which scientists named Booster, also increased the biomass of another plant species, Arabidopsis, or thale cress, indicating the potential for higher yields from other crops if successful on a larger scale. 

Booster was identified in Populus trichocarpa, or the black cottonwood tree, a species that thrives from Baja California in Mexico into northern Canada. This tree is recognized as a leading candidate as a feedstock for making biofuels and bioproducts.

Booster is a chimeric gene that contains sequences from three originally separated genes, and has been preserved in poplar with minimal changes over evolutionary time. The gene plays an important role in photosynthesis, the process plants use to convert sunlight, carbon dioxide and water into glucose ­— the building block for cellulose, starch and other macromolecules related to food and fuel production. 

Chimeric genes have unique origins and are thought to enable evolutionary changes that help plants adapt to new environments. In the case of Booster, the ORNL team determined that it contains three different DNA origins. One segment is from a bacteria found in the poplar tree’s root system; one segment is from an ant that farms a fungus known to infect poplar; and one segment is from the large subunit of Rubisco, an abundant protein found in plant chloroplasts.

Chloroplasts are the principal cell structures that house the photosynthetic apparatus converting light energy into the chemical energy that fuels plant growth. The Rubisco protein functions as the plant’s “carbon-grabber,” capturing carbon dioxide from the atmosphere. Scientists have for years been working on ways to boost the amount of Rubisco in plants for greater crop yield and absorption of atmospheric CO2.
When researchers created poplar trees with greater expression of the Booster gene, their Rubisco content and subsequent photosynthetic activity soared, resulting in plants that were as much as 200% taller when grown in greenhouse conditions, as described in the journal Developmental Cell. The trees demonstrated up to 62% more Rubisco content and about a 25% increase in net leaf CO2 uptake. In field conditions, scientists found that higher expression of Booster resulted in poplar trees up to 37% taller, with as much as 88% more stem volume, increasing biomass per plant.

Scientists inserted Booster in a different plant, Arabidopsis, resulting in a similar increase in biomass and a 50% increase in seed production. This finding indicates the wider applicability of Booster to potentially trigger higher yields in other plants.