Scientists advance understanding of C4 photosynthesis

Discovery about the evolution of C4 photosynthesis could pave the way for the development of more resilient and productive agricultural crops, especially in a context of climate change.

The research reveals how plants that use C4 photosynthesis have evolved to achieve superior efficiency. And how this natural technology can be adapted to benefit plants that still rely on C3 photosynthesis, such as rice, wheat and soybeans.

C4 photosynthesis: an evolutionary leap

Most plants, about 95%, use the C3 photosynthesis method. This process has important deficiencies, such as loss of energy and water, which makes them more vulnerable in hot and dry climates.

On the other hand, C4 photosynthesis, which emerged about 30 million years ago, is 50% more efficient, conserving energy and reducing water loss.

This efficiency is achieved with the involvement of bundle sheath cells, which take over part of the photosynthesis process alongside the mesophyll cells. However, the molecular mechanism that enabled this transition in C4 plants has always been a mystery, until now.

The key is in the regulatory factors

Using single-cell genomics technology, the researchers analyzed C3 (rice) and C4 (sorghum) plants. They found that the evolution of C4 photosynthesis did not depend on the emergence of new genes, but on changes in the regulatory elements that control gene expression.

A group of proteins known as DOF ​​transcription factors have been identified as crucial for activating genes required for photosynthesis in bundle sheath cells.

These regulatory elements already existed in ancestral C3 plants, but were "co-opted" during evolution to expand their functions in C4 plants. This suggests that the potential for C4 photosynthesis is already embedded in C3 plants, offering a promising opportunity for genetic manipulation.

Applications in agriculture

Scientists are now exploring how to apply these discoveries to transform essential crops into more resilient plants. The C4 Rice Project is a global effort to introduce C4 photosynthesis traits into rice, aiming to increase its productivity and water efficiency.

In the short term, the study strengthens the Salk Institute's initiative to create optimized plants that can better withstand climate change and help capture carbon.

More information can be found at doi.org/10.1038/s41586-024-08204-3