Text by Julia Quintana González and photo by María Sanz Arnal
Photosynthesis is the evolutionary mechanism that sustains life on Earth as we know it. We breathe and eat thanks to photosynthesis. It’s that simple. Basically, photosynthesis is the process by which light is used to generate energy in the form of carbohydrates. Only plants, green algae, and some bacteria can do this. To do so, they need light, water, and carbon dioxide. And, for photosynthesis to continue, water is transformed into oxygen, which we breathe. In the first step of photosynthesis, energy is produced from light, and in the second step, that energy is used to make glucose. Since glucose needs carbon to form, carbon dioxide is used to obtain the necessary molecules to produce glucose in a process called the Calvin Cycle, which uses a molecular machine called RuBisCo. When oxygen and carbon dioxide are present inside the cell, RubisCo can divide its work between these two molecules. This division of labour results in a lower amount of glucose being generated, and therefore, photosynthesis is less efficient.
There are many fascinating aspects of photosynthesis. In fact, it can be studied from any disciplinary angle: biochemical, physiological, biophysical, environmental, taxonomic, molecular, botanical… You’ll understand, then, why we as researchers and teachers are so passionate about this topic. Today, there are significant efforts underway to increase crop yield and resilience through improvements aimed at boosting their photosynthetic capacity. To get the most out of this strategy, we need to understand and characterize this metabolic process in depth. However, this task is not easy. In fact, the more we learn about photosynthesis, the less we know. This often happens in science.
Photosynthesis is a flexible metabolic process. That is, not all plants use the same strategy or regulate their photosynthetic machinery in the same way. On the one hand, we have the plants known as C3 plants, the majority (85%). Plants like wheat, soya bean, and rice. These plants have a photosynthetic mechanism that works well in temperate and humid climates. Basically, all photosynthesis occurs within the same cell. While this is very efficient, it doesn’t work for all plants. Those that live in warmer or drier environments need to make adjustments because their RuBisCo enzyme works more efficiently for oxygen than for carbon dioxide. These adjustments involve concentrating the carbon to separate it from the oxygen. This way, RuBisCo works only with carbon dioxide, and photosynthesis becomes more efficient. Species with these adjustments can be divided into two main groups: C4 and CAM. C4 plants, like corn or tiger nut, perform part of their photosynthesis in other cells. CAM plants, like agave, perform part of their photosynthesis at night. Adjusting such a crucial process has been an evolutionary step that has taken millions of years.
For three days, scientists from around the world gathered to discuss and reflect on the evolution of C4 photosynthesis. Thanks to the sponsorship of the Global Change Research Institute, we brought together experts from many countries to share their groundbreaking and disruptive ideas. We also asked them to help us envision new horizons in the field of C4 photosynthesis research. We wanted our team to be representative of all stages of the research career and ensured cultural and gender diversity. Thanks to this approach, we were able to establish professional synergies, prepare a draft of a scientific review on this topic, and promote multilateral training projects for young researchers. Finally, we sat down and disconnected from the daily rush and multitasking to enjoy talking about science in the historic setting of Aranjuez.