Fig. 1. Activation of the cytosolic kinase domain of MIK2 induces SCOOP expression.
a Diagram of the RLK7ECD-MIK2TK chimeric receptor gene. RLK7ECD-MIK2TK chimeric gene encoding RLK7 extracellular domain (RLK7ECD) and MIK2 transmembrane and cytoplasmic kinase domains (MIK2TK) and the full-length RLK7 (RLK7ECD-RLK7TK) driven by the CaMV35S promoter were transformed into rlk7. b, c RLK7ECD-MIK2TK/rlk7 transgenic seedlings show more severe root growth inhibition to PIP1 treatment than RLK7/rlk7 seedlings. Images of 10-day-old seedlings of Arabidopsis WT (Col-0), rlk7, two representative lines (L9 and L16) of RLK7ECD-MIK2TK/rlk7, and two lines (L4 and L5) of RLK7/rlk7 grown on ½MS plates with or without 1 µM PIP1: red stars indicate the root tips, scale bar, 4 mm (b; quantification of root length of seedlings (c)). d PIP1 treatment induces a more pronounced ROS production in RLK7ECD-MIK2TK/rlk7 than that in RLK7/rlk7 transgenic seedlings. One-week-old seedlings grown on ½MS plates were treated with H2O or 100 nM PIP1, and ROS production was calculated as the total relative luminescence units (RLU) (see “Methods” for details). e PIP1 treatment induces the expression of SCOOP genes in RLK7ECD-MIK2TK/rlk7 transgenic plants but not in WT plants. Ten-day-old seedlings grown on ½MS plates were treated with 1 µM PIP1 for 0, 1, and 6 h for RNA-Seq analysis. Heatmap represents adjusted log2-transformed transcript levels of SCOOPs and STMPs (see “Methods” for details). The box plots in (c) and (d) show the first and third quartiles as bounds of box, split by the medians (lines), with whiskers extending 1.5-fold interquartile range beyond the box, and minima and maxima as error bar. Different letters indicate a significant difference with others (P < 0.05, one-way ANOVA followed by Tukey’s test, n = 28, 26, 15, 15, 15, 13, 15, 16, 15, 14, 15, 15 for plots from left to right in (c), n = 3, 4, 3, 4, 3, 5, 3, 5 for plots from left to right in (d)). The experiments in (b–d) were repeated three times with similar results.