The common weed may be a ‘super plant’ that holds the key to drought-tolerant crops

A common weed holds important clues on how to create drought-tolerant crops in a world beset by climate change.

Yale scientists describe how Portulaca oleraceacommonly known as purslane, integrates two distinct metabolic pathways to create a new type of photosynthesis that allows the weed to withstand drought while remaining highly productive, they report Aug. 5 in the journal Science Advances.

It’s a very rare combination of traits and has created a sort of ‘super plant’ – which could potentially be useful in endeavors such as crop engineering,” said Yale professor Erika Edwards. ecology and evolutionary biology and senior author of the article. .

Plants have independently evolved a variety of distinct mechanisms to enhance photosynthesis, the process by which green plants use sunlight to synthesize nutrients from carbon dioxide and water. For example, corn and sugar cane have developed what is called C4 photosynthesis, which allows the plant to remain productive at high temperatures. Succulents such as cacti and agaves have another type called CAM photosynthesis, which helps them survive in deserts and other areas with little water. C4 and CAM perform different functions but recruit the same biochemical pathway to act as “add-ons” to regular photosynthesis.

What makes weed purslane unique is that it has both of these evolutionary adaptations – allowing it to be both highly productive and highly drought tolerant, an unlikely combination for a plant. Most scientists thought that C4 and CAM worked independently in purslane leaves.

But the Yale team, led by co-corresponding authors and postdoctoral researchers Jose Moreno-Villena and Haoran Zhou, conducted a spatial analysis of gene expression in purslane leaves and found that C4 activity and CAM are fully integrated. They operate in the same cells, with the products of CAM reactions being processed through the C4 pathway. This system provides unusual levels of protection for a C4 plant in times of drought.

The researchers also constructed metabolic flux models that predicted the emergence of an integrated C4+CAM system that mirrors their experimental results.

Understanding this new metabolic pathway could help scientists design new ways to engineer crops such as corn to help withstand prolonged drought, the authors say.

In terms of engineering a CAM cycle in a C4 crop, like maize, there is still a lot of work to do before this becomes a reality, Edwards said. “But what we’ve shown is that both paths can be effectively integrated and share products. C4 and CAM are more compatible than we thought, leading us to suspect that there are many other C4+CAM species out there, waiting to be discovered.

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