Analysis of dynamic gene expression responses to altered gravity in the wildtype and auxin efflux carrier mutants of the model plant Arabidopsis thaliana

Plant roots are among most intensively studied biological systems in gravity research. Altered gravity induces asymmetric cell growth leading to root bending. Differential distribution of the phytohormone auxin underlies root's responses to gravity being coordinated by auxin efflux transporters from the PIN family. The objective of this study was to compare early transcriptomic changes in roots of Arabidopsis thaliana using experiments on board of parabolic flights, suborbital and orbital flights, and ground-based facilities for simulated microgravity conditions to correlate these changes to auxin distribution. By comparing immediate and initial responses of the gene expression to the different gravitational forces identified primary gravity regulated genes and resolved time-effects in gene expression leading to an understanding of the underlying physiological responses and adaptive processes. High-resolution imaging in combination with computational approaches further resolved phenotypic changes initiated by altered gravity at the cellular level. Our study provides important insights towards understanding signal transduction processes in altered gravity conditions by combining experimental platforms with the analysis of different genetic mutants in the model Arabidopsis.