Fig. 5: Localized expression of triterpenoid biosynthetic genes in response to GMI1000.

a A simplified pathway shows the key enzymes catabolizing the biosynthesis of two triterpenoid products (thalianin and arabidin). b Several triterpenoid biosynthetic genes are strongly induced by GMI1000 but not WCS417. c The expression pattern of pTHAS1::YFP-NLS in root maturation zone, Maximum projections of transverse sections are shown. Yellow arrows indicate atrichoblast cells or cortex cells. Scale bars, 20 μm. The experiment was repeated 3 times with similar results. d–f Z-score normalized expression heatmap illustration of the expression patterns of THAR1, THAR2, THAH, and THAS1. g Validation of the maturation cell-specific induction pattern of THAS1 using its promoter-driven reporter line (pTHAS1::YFP-NLS), roots were inoculated with mock (10 mM MgSO₄) or GMI1000 (OD₆₀₀ = 0.05) for 6 h. Images correspond to the meristematic zone (MZ), elongation zone (EZ), and maturation zone (MZ). The scale bar represents 50 μm. h Quantitative analysis of YFP signal intensities of the THAS1 reporter line after different treatments and from different regions. n = 6 from two independent experiments. Results are presented as mean ± standard error of the mean (SEM). Different letters indicate statistically significant differences (P < 0.05) between means by ANOVA and Tukey’s test. Box plots show the median (horizontal bar), 25th (bottoms of boxes), and 75th (tops of boxes) quartile range (QR), and non-outlier data value (upper and lower whiskers) of each index.