Comparison of low water potential (drought) regulated gene expression in wild type (Col-0) and egr1-1egr2-1 (At3g05640/At5g27930) mutant.

Two Clade E Growth Regulating PP2Cs EGR1 and EGR2 (EGR1, At3g05640; EGR2, At5g27930) are strongly up regulated by low water but much less affected by ABA. EGR mutants maintained higher seedling root elongation and dry weight at low water potential and higher levels of stress protective metabolite proline. Phosphoproteomics of egr1egr2 double mutant showed an increased phosphopeptide abundance of several cytoskeleton and plasma membrane-associated proteins, and consistent to this, egr mutants had more extensive microtubules recovery during low water potential acclimation. Microarray experiments were used to identify genes differentially expressed in egr1-1egr1-2 (SALK_011589/salk_048861) versus wild type under both unstress control conditions and after low water potential (ie: drought, water deficit). A relatively long term (96 h) low water potential treatment was used as phenotypes of egr1-1egr2-1 were most apparent after this longer term low water potential treatment. Seven-day-old seedlings of wild type (Col-0) or egr1-1egr1-2 were transferred from agar plates of control media to low water potential stress (PEG-infused agar plates at -1.2 MPa) or to fresh control media (-0.25 Mpa). Samples (whole seedlings) were collected 96 h after transfer. Three independent experiments were conducted with one sample of each treatment (wild type stress and control, egr1-1egr2-1 stress and control) collected from each experiment. Gene expression data of Col-0 samples were the same set of samples which were previously (GSE35258) compared with the gene expression of Clade A PP2C, Highly ABA Induced 1 (HAI1). Microarray experiments of Col-0, hai1-2 and egr1-1egr2-1 were performed at the same time. Here, we are using same set of Col-0 expression profile to compare with the expression profile of egr1egr2.