Cytosolic calcium, hydrogen peroxide and related gene expression and protein modulation in A rabidopsis thaliana cell cultures respond immediately to altered gravitation: parabolic flight data

Callus cell cultures of A rabidopsis thaliana (cv. C olumbia) were exposed to parabolic flights in order to assess molecular, short‐term responses to altered gravity fields. Using transgenic cell lines, hydrogen peroxide ( H 2 O 2 ) and cytosolic C a 2+ were continuously monitored. In parallel, the metabolism of samples was chemically quenched ( RNA later, A mbion for RNA ; acid/base for NADPH , NADP ) at typical stages of a parabola [1  g before pull up; end of pull up (1.8  g ), end of microgravity (20 s) and end of pull out (1.8  g )]. Cells exhibited an increase in both C a 2+ and H 2 O 2 with the onset of microgravity, and a decline thereafter. This behaviour was accompanied by a decrease of the NADPH / NADP redox ratio, indicating C a 2+ ‐dependent activation of a NADPH oxidase. Microarray analyses revealed concomitant expression profiles. At the end of the microgravity phase, 396 transcripts were specifically up‐, while 485 were down‐regulated. Up‐regulation was dominated by C a 2+ ‐ and ROS ‐related gene products. The same material was also used for analysis of phosphopeptides with 2‐ D SDS PAGE . Relevant spots were identified by liquid chromatography– MS . With the exception of a chaperone ( HSP 70‐3), hypergravity (1.8  g ) and microgravity modified different sets of proteins. These are partly involved in primary metabolism (glycolysis, gluconeogenesis, citrate cycle) and detoxification of ROS . Taken together, these data show that both gene expression and protein modulation jointly respond within seconds to alterations in the gravity field, with a focus on metabolic adaptation, signalling and control of ROS .