Engineered Increase in Mesophyll Conductance Improves Photosynthetic Efficiency in Field Trial

It is possible to engineer increased mesophyll conductance in plants according to new research from the University of Illinois. Mesophyll conductance plays a key role in photosynthesis and refers to the ease with which CO₂ can diffuse through a leaf's cells before reaching the location where it is ultimately turned into sugar to feed the plant (carbon fixation).

CO₂ faces barriers as it moves through the leaf, including its own cell walls. Researchers from the Long Lab found that by increasing permeability and slightly reducing the thickness of cell walls, they could increase CO₂ diffusion and uptake in a model crop.

"This is one of the few successful tests of concept showing that we can engineer an increase in mesophyll conductance and have it result in increased photosynthesis in the field," said Coralie Salesse-Smith, a postdoctoral researcher in Long Lab and lead author on a paper about the research, published in the Plant Biotechnology Journal.

"Theory shows us that increasing mesophyll conductance to increase photosynthesis can be achieved without the cost of more water. This is important considering the urgent need for increased crop production and sustainable water use."

Photosynthesis is the natural process all plants use to convert sunlight, water, and carbon dioxide into energy and yields. CO₂'s journey to becoming useful sugar (energy) for the plant, begins when it passes through tiny holes in the leaves known as stomata.

In order for the CO₂ to reach the chloroplast, (where it is turned into sugar), it must travel through a number of barriers, including the cell wall. The team hypothesized that if they could improve CO₂ diffusion across the cell wall by making these barriers easier to cross, it would improve mesophyll conductance and in turn photosynthetic efficiency. Increasing mesophyll conductance means that more CO₂ will be available for the plant to turn into food.