Fig. 3: HAN is required for QC and CSC identity in the columella stem cell niche.
a–e, Representative DIC images of root tips of the indicated genotypes. QC184 signal after GUS staining is shown in blue and starch granules labelled by lugol staining in purple. Dashed lines mark QC cells (white), columella stem cells (yellow) and upper layers of differentiated CCs (red). In a, d and e, images are representative of n > 20 independent roots measured and producing similar results. In b and c, images are representative of n = 69 independent roots measured; of these, 30 roots expressed QC184 and 39 roots did not. f, Representative confocal images showing ectopic starch grains at the CSC position (yellow arrowheads) of the indicated genotypes after mPS-PI staining of 6-day-old roots. The position of the QC is indicated (white arrowheads). g, Representative confocal images showing cell walls indicative of QC divisions (red arrowheads) of the indicated genotypes after mPS-PI staining of 6-day-old roots. The position of the QC is indicated (white arrowheads). h, Percentages of roots with different numbers of starch-free layers below the QC in 6-day-old WT (n = 83), han-30 (n = 110), wox5-1 (n = 105) and wox5-1 han-30 (n = 51) roots. P values comparing presence vs absence of starch-free CSC layers using a two-sided Fisher’s exact test with Bonferroni correction for multiple testing: ****PCol-0 vs han-30 = 0.00004, ****PCol-0 vs wox5-1 = 0.00004, ****PCol-0 vs wox5-1 han-30 = 0.00004, **Phan-30 vs wox5-1 = 0.0064, NSPhan-30 vs wox5-1 han-30 = 0.126. i, Percentages of QC division in 6-day-old WT (n = 80), han-30 (n = 89), wox5-1 (n = 96) and wox5-1 han-30 (n = 48) roots. ***PCol-0 vs han-30 = 0.0004, ***PCol-0 vs wox5-1 = 0.0004, ***PCol-0 vs wox5-1 han-30 = 0.0004, NSPhan-30 vs wox5-1 = 0.2122, NSPhan-30 vs wox5-1 han-30 = 0.0556 using a two-sided Fisher’s exact test with Bonferroni correction for multiple testing. j,k, Representative confocal images showing expression of the CSC marker J2341:GFP in WT (j) and han-30 (k). Images are representative of n = 28 (Col-0) and n = 25 (han-30) independent roots measured and producing similar results. Scale bars, 20 μm.
