Fig. 1: KOIN functions to restrict root meristem size and is localized to the inner lateral domain in endodermal cells.

a Confocal images of the median longitudinal sections of root tips with cells highlighted: quiescent center (QC, cyan), meristematic cortex (orange), and T-junctions (pink arrowheads). Quantification of b cortex cell number and c distance to the uppermost T-junction over time 5–7 days post-stratification (d.p.s.). Box plots show data from a single biological replicate representative of three with similar results (n = 20 per genotype). Boxes delimit upper and lower quartiles, median values are indicated with a line, and single values are shown as dots. Bars indicate max/min values and **** statistical significance P value < 0.001 (two-way ANOVA using Turkey’s multiple comparison test). d, e Confocal images of WT root meristems at 6 d.p.s. Adjacent panels show merged images of green fluorescent protein (GFP, fluorescence intensity color scale) and stained with propidium iodide (PI, gray scale) followed by GFP alone. d Median longitudinal and e transverse sections showing accumulation of KOIN-GFP driven by KOINp. Inset in (d) KOIN-GFP accumulation in the CEI. f Schematics summarizing endogenously expressed IRK-GFP localization (green) and KOIN-GFP (purple). g Quantification of cortex cell number and distance to the uppermost T-junction at 7 d.p.s. in koin-1 expressing KOIN-GFP driven by KOINp or SCRp normalized to Col-0. Data from n = 20 per genotype for a single biological replicate representative of 3 with similar results. Boxes delimit upper and lower quartiles, median values are indicated with a line, and single values are shown as dots. Bars indicate max/min values and **** statistical significance P value < 0.001 (one-way ANOVA using Dunnett’s multiple comparisons test). h Median longitudinal sections of WT roots with KOIN-GFP driven by SCRp. Cellular abbreviations: CEI cortex/endodermal initial, CEID CEI daughter, E endodermis, C cortex, Ep epidermis, X xylem axis, P pericycle. White arrowheads highlight KOIN-GFP localization to the inner lateral domain in the endodermis. Images displayed in this figure are representative of observations in experiments replicated at least 3 times with each replicate containing at least ≥15 plants/genotype. Scale bars: a 50 µm; d, e, g 20 µm.