Abstract
Understanding the effects of space radiation and microgravity on DNA is critical to assessing the impact of long-term spaceflight. While experiments performed in space constitute the most effective means of examining these effects, opportunities are limited and costly. As this bottleneck will likely continue for the foreseeable future, data from past experiments represent a particularly valuable source of information for continuing studies. To this end, NASA created GeneLab, a public Omics database for spaceflight-related data. We used data from GeneLab to examine the effect of spaceflight on DNA mutation rates. Optimally, mutation rates are estimated using DNA sequence data directly. Unfortunately, to date, few DNA-based datasets appear in GeneLab. Transcript data, however, is abundant. Here we used RNA-Seq data to examine DNA sequence variation in Arabidopsis thaliana seedlings grown aboard the International Space Station (ISS) vs. on the ground. ISS-based samples were grown under two conditions: spaceflight under microgravity, and, by using a specialized onboard centrifuge under induced gravity. This powerful experimental design allowed us to separate the effects of microgravity from non-microgravity spaceflight stress, such as space radiation. More mutations were observed in spaceflight samples than in ground control samples, with transversion mutations being overly represented. Mutation rates identified in samples grown under artificial gravity in space were similar to that of microgravity spaceflight samples, indicating that microgravity exposure played a limited role. This work demonstrates that RNA-Seq data is useful for evaluating DNA damage from spaceflight and provides insight into the types of mutations that occur.