A plant’s survival is largely impacted by its ability to sense and respond to gravitational changes, such as the changes that occur in spaceflight. However, the gravitropic signaling pathway is not fully understood. In the BRIC-20 experiment aboard the International Space Station, the Arabidopsis proton pump AHA2 was found to be differentially phosphorylated in microgravity compared to ground controls. AHA2 is hypothesized to be involved between plant hormone movement and differential growth during gravity signaling. When subject to reorientation, aha2 mutant seedlings had increased root curvature compared to wild type. Furthermore, wild type seedlings treated with fusicoccin, a phytotoxin that increases AHA2 phosphorylation and activity, had increased root curvature compared to untreated plants. To determine the role of AHA2 phosphorylation in gravitropic signaling, several lines of transgenic Arabidopsis with modifications in phosphorylation sites are being developed. The transformants will then be phenotyped for altered gravity response, showing if the phosphorylation of the AHA2 protein is involved in a plant’s gravity response. These findings will further knowledge on the molecular mechanisms of gravitropism to develop space-tolerant plants for life support in spaceflight and for habitation of the moon, Mars, and beyond.