Title : Spaceflight and microgravity response of plant telomeres and telomerase
Abstract:
To realize NASA’s goal of human colonization of Mars and the Moon by 2050, plants will be required for food production, carbon dioxide removal, oxygen production and water purification. Understanding plant adaptation to spaceflight is therefore essential for human space expansion. While little is known about plant responses to spaceflight, transcriptomic data showed the upregulation of multiple stress response pathways, including genomic and oxidative stress. Telomeres are essential structures that safeguard genome stability and are an important biological marker of survivability. Prior studies revealed that astronauts aboard the International Space Station (ISS) experienced increased telomere length and oxidative damage to their genomes during spaceflight. Here we set out to investigate telomere length homeostasis in relationship with cellular stress in Arabidopsis thaliana seedlings grown for 12 days either in orbit aboard the ISS, or under simulated microgravity conditions produced by a Random Positioning Machine. We report a substantial increase in telomerase enzyme activity in seedlings grown under spaceflight conditions as compared to both 1g ground controls and simulated microgravity. Despite the dramatic increase in telomerase activity we did not detect a significant change in telomere length. However, we found elevated levels of 8-oxoguanine in the DNA of seedlings grown aboard the ISS, as well as increased mitochondrial DNA, consistent with oxidative damage. These findings support previous omics analyses predicting spaceflight-induced oxidative stress in Arabidopsis. We postulate that increased telomerase activity in space-flown Arabidopsis is a response to excess ROS generated from the ionizing radiation environment of low Earth orbit, and may reflect a broader role for telomerase in the stress response. Altogether, our data indicate that plants have a robust mechanism of telomere maintenance, resulting in negligible telomere length fluctuations during spaceflight and microgravity conditions. These observations suggest that plants may be well-equipped to survive the stresses imposed by interstellar colonization.
