PHOTOTRANS

Evolvability and drivers of photosynthetic transitions in flowering plants

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 Obiettivo del progetto (Objective)

'Several carbon concentrating mechanisms (CCM) have evolved to counteract the deficiencies of the classical photosynthetic pathway (C3 photosynthesis). Their multiple origins represent one of the most striking examples of convergent evolution and make them especially suitable for comparative evolutionary studies. In land plants, the two main CCM are CAM and C4 photosynthesis, which confer an advantage in arid and warm environments. These CCM are ecologically and economically very important, but their evolutionary history remains poorly understood. In particular, the number of transitions between the different photosynthetic types and their directions are still unknown. In this project, a multi-scale phylogenetic approach will be used to address the evolvability and reversibility of the different photosynthetic types together with the factors that influence the probability of a given plant group evolving one or the other CCM. Using two plant groups with a high variability in the photosynthetic types (Poaceae and core Caryophyllales), the genetic changes on an enyzme involved in both CAM and C4 pathways will be identified and, in combination with species phylogenies, will serve to retrace past photosynthetic transitions. The effect of different plant characteristics on CCM evolvability will be tested through comparative analyses in the generated phylogenetic framework. This approach will finally be transferred to a grass genus extremely variable in its photosynthetic characteristics, to shed light on CCM microevolutionary processes. Overall, this project will bring important insights about the causes and consequences of one of the greatest ecological and evolutionary successes in plant history.'

Introduzione (Teaser)

Plants in hot and arid climates have evolved multiple times, one of two different mechanisms to concentrate carbon for photosynthesis. Researchers are now investigating the underlying causes of this striking example of convergent evolution.

Descrizione progetto (Article)

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.