Drying without dying: Desert moss holds the key to drought tolerance

Deep in the desert, where water is rare and plants fight to stay alive, a tiny moss called Syntrichia ruralis holds on. Unlike other plants, this moss can survive without water for a long time. 

Syntrichia ruralis dries up completely, but when it rains again, it comes back to life. This amazing ability to survive tough conditions made scientists from Cornell University curious to learn about it. 

Drying without dying

Plants, especially mosses and some other species, have a remarkable ability to withstand extreme dryness, almost losing all of their water content. This doesn’t kill them, but puts them in a kind of dormant state where they barely function. 

When water becomes available again, the plants wake up and start growing and functioning normally as if nothing ever happened. This ability, called “drying without dying,” is not just a quirk but a crucial survival strategy that allows some plants to live in very dry places where water is scarce and unpredictable. 

Two special proteins

The researchers discovered two crucial sets of genes in the moss Syntrichia ruralis that enable it to adapt to weather dry spells. These genes code for proteins that play a vital role in the moss’s survival during dehydration.

LEA proteins, found in many plants, act as cellular protectors against drying. They function by stabilizing essential cellular components like proteins, membranes, and even DNA. This ensures these elements remain operational even when water is limited.

The other group, ELIP proteins, are typically associated with response to bright light. However, in S. ruralis, they offer an additional layer of protection during dry periods. These proteins shield the delicate machinery of photosynthesis from damage caused by excessive light, especially under water scarcity conditions.

Transcription factor

Joining the moss’s defense team in this drought survival strategy is a protein aptly named R2R3 MYB transcription factor. This protein acts like the master conductor, controlling the genes vital for the moss’s resilience against dehydration.

Similar to protein supervisors, transcription factors dictate which “instructions” are followed in the cell. They do this by attaching to specific regions of the moss’s DNA, essentially turning “on” or “off” the production of proteins encoded by those genes. By orchestrating a response to the stress of drought, the proteins allow S. ruralis to adapt.

A novel discovery 

The experts discovered a protein named MYB55 in the moss. This protein plays a crucial role in how the moss manages stress, particularly during dry periods. MYB55 acts as a regulator, similar to a brake, on other genes that become active when the moss experiences dryness. This helps the moss maintain a balanced response, effectively dealing with the dry conditions without causing harm to itself.

MYB55 has a fine-tuning mechanism, preventing the moss from overreacting to drought. This ensures the moss doesn’t waste energy or damage its cells by attempting an overly aggressive response. Moreover, it helps the moss avoid overreaction to stress. In plants, an excessive stress response can be detrimental, and MYB55 helps ensure the defensive mechanisms are proportionate to the level of stress encountered.

According to Cornell University’s postdoctoral researcher Xiaodan Zhang, the discovery of MYB55 “provides insights into the evolution of plant stress responses and how certain key genes have been preserved and repurposed throughout evolutionary time.”

Broader implications

Understanding how mosses cope with drought could help us develop crops with similar tolerance, improving food security and sustainability, especially in regions facing increasing drought due to climate change. While the idea of learning from mosses for hardier crops might raise eyebrows, 

Dr. Melvin Oliver is a retired USDA researcher and current adjunct professor at the University of Missouri-Columbia who has studied these mosses for 40 years.

“I’d take this dried up little piece of moss and put it in their hand and then squirt a bit of water on it, and thirty seconds later you’ve got this bright little green plant that’s perfectly alive… It’s basically, how do plants survive drying?” said Dr. Oliver.

Furthermore, the research also aids in developing strategies to adapt to climate change. It emphasizes the importance of biological research in mitigating the impact of environmental changes.

The research is published in the journal New Phytologist.

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