The evolution of photosynthesis
Certain groups of plants have evolved carbon concentrating mechanisms (CCMs) to account for deficiencies in the conventional photosynthetic pathway known as 'C3 photosynthesis'. This has resulted in alternative forms of photosynthesis, called 'CAM' and 'C4 photosynthesis'. Interestingly, the same CCMs have evolved independently in different groups, indicating that there are common environmental or plant traits driving this convergence.The EU-funded 'Evolvability and drivers of photosynthetic transitions in flowering plants' (PHOTOTRANS) project aimed to use phylogenetic analysis to understand the evolutionary driving factors of C4 and crassulacean acid metabolism (CAM). They achieved this by studying the genetic changes in an enzyme important for photosynthesis in these CCMs.The research confirmed that these evolutionary changes happened independently in different plant groups multiple times over the last 35 million years. PHOTOTRANS revealed that identical groups of genes were co-opted for C4 photosynthesis in separate groups of plants; this group of genes is also involved with CAM.Sophisticated statistical analysis showed that decreased atmospheric carbon dioxide was a precondition for the evolution of C4. Researchers further found that C4 and CAM photosynthesis could only evolve in plants with a particular leaf anatomy.PHOTOTRANS has shown that this unusually common convergent evolution is a result of both physiological and environmental conditions. This knowledge has improved our understanding of how convergent evolution of important plant features occurs.
