How Plants Protect Their DNA in Space 


The NASA Twins Study published in 2019 compared biological changes in identical twin astronauts Scott and Mark Kelly.1  The former spent a year on the International Space Station (ISS) and the latter remained Earthside. Among other differences, Scott’s telomeres grew longer while he was in space and shortened once he returned to Earth.

Like many researchers in the telomere field, Dorothy Shippen, who is a plant telomere biologist at Texas A&M University, was intrigued. Telomere changes in response to the environment can influence an organism’s survival under stress, and plant environmental stress resilience is an essential component of both future long-duration space travel and current agriculture challenges on Earth. Although plants have made the trip to the ISS many times, the effects of spaceflight on plant telomeres remained a mystery until recently. 

Dorothy Shippen (left) and Borja Barbero Barcenilla (right)

Dorothy Shippen and Borja Barbero Barcenilla investigated telomere maintenance in Arabidopsis thaliana grown aboard the ISS. 

Texas A&M University 

In their latest work published in Nature Communications, Shippen and postdoctoral researcher Borja Barbero Barcenilla investigated telomere maintenance in Arabidopsis thaliana grown aboard the ISS.2 Similar to spaceflight’s effects on humans, the space seedlings had increased telomerase activity, the enzyme that lengthens telomeres. However, unlike human astronauts, the ISS plants showed no change in telomere length. 

Q: How did you begin investigating plant telomeres from the ISS?

Shippen: The Twins Study was really inspirational for us, but I had no access to sending plants into space. It was just a curiosity. We contacted NASA and asked if there were any samples of plant material that we could analyze for telomere changes. It turned out that Sarah Wyatt, a plant molecular biologist studying gravity’s effects on plant growth at Ohio University, and her team had just had a flight and had some extra material. We collaborated with Wyatt and with Susan Bailey, a radiation cancer biologist at Colorado State University who led the telomere-related portion of the NASA Twins Study. We collected some data from the existing extra material and also got additional samples later because they had to rerun a flight. 

Q: Were there any unique logistical challenges to working with ISS samples?

Every experiment was a wonderful, unique opportunity. It was a mix of this divine wonder and making sure not to screw it up because there was no more of the sample.
-Borja Barbero Barcenilla, Texas A&M Universit

Barbero: There were many challenges. When the additional samples were about to be launched, there were around 60 Arabidopsis agar plates with around 18 seedlings per plates. It was a lot of plates to get ready in a span of three to four days. I helped Alexander Meyers, the postdoctoral researcher from Wyatt’s laboratory who currently works at NASA and is a coauthor of this article. 

Once the samples came back here to Earth, we wanted to separate the shoots from the roots because those different tissues could have different responses. Due to microgravity, the roots and the shoots really grow all over the place; they interlock. I was scared to dissect it because it was a unique tissue. We had to dissect the tissue very quickly after taking it out of the freezer. 

We invited Meyers to Texas A&M University to help us with the dissection, and as scary as it was, it was just a wonderful day. As we prepped the experiment and took the samples out of the freezer, I looked at the sample thinking, “This has been in space!” It was such a cool feeling. Every experiment was a wonderful, unique opportunity. It was a mix of this divine wonder and making sure not to screw it up because there was no more of the sample.

See Also “Whenever, Wherever: Taking DNA Amplification Outside the Lab”

Borja Barbero Barcenilla and Alexander Meyers, in front of NASA Headquarters (Kennedy Space Center)

Borja Barbero Barcenilla and Alexander Meyers prepared the seedlings sent to the ISS in June 2021 aboard the SpaceX CRS 22 resupply mission. 

Borja Barbero Barcenilla

Q: Did any of the findings surprise you?

Barbero: We had anticipated a telomere length increase. When the telomere length did not change, I was very puzzled. But this is actually much cooler than what we expected. Every other organism that has flown to space has these changes in telomere length, and plants do not.

Shippen: Caenorhabditis elegans went to space before, and its telomeres also got longer, just like human telomeres. Human telomeres are very dynamic; they get longer and shorter in response to a variety of different environmental assaults or physiological changes. When we put plants in different kinds of stress conditions, we see that their telomeres often do not change, so we didn’t really know what was going to happen in space. It wasn’t completely surprising that there was no change in telomere length. The surprise was how much telomerase was induced. 

Q: Why was it surprising to see telomerase induction without telomere lengthening?

Shippen: It means that telomere length and telomerase activity are uncoupled, which was not expected because in human cells, it is completely coupled. We started thinking more broadly about the activation of telomerase in response to stress. We conducted additional experiments to look at the response of telomerase in different kinds of stress conditions, which we could do on Earth in our own lab, and we still saw this induction of telomerase.

It led us to think that maybe telomerase has additional roles, which is a controversial idea in the field. Many scientists are not sure what to think about potential extra-telomeric functions for telomerase. But it is hard to understand why the enzyme activity would go up so dramatically, and in our case, not result in any change in telomeres. We plan to follow up on that.

See Also “Illuminating the Plant Gene Map”

This interview has been condensed and edited for clarity.

References

  1. Garrett-Bakelman FE, et al. The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight. Science. 2019;364(6436):eaau8650.
  2. Barcenilla BB, et al. Arabidopsis telomerase takes off by uncoupling enzyme activity from telomere length maintenance in space. Nat Commun. 2023;14(1):7854.

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