Fig. 6: Cellular features and developmental processes of hairs and expression patterns of key candidate genes in Nigella integrifolia petals.

a The distribution of Type 1 hairs (T1Hs), Type 2 hairs (T2Hs), and pavement cells (PCs) on a mature petal under stereomicroscope and scanning electron microscope. Numbered regions (1–2) are magnified to show T1Hs/PCs and T2Hs, respectively. b, c Semi-thin sections of regions containing T1Hs/PCs (b) and T2Hs (c). d Total numbers of T1Hs and T2Hs on each petal. e Lengths of T1Hs and T2Hs. f, g Propidium iodide (PI) staining of T1Hs/PCs (f) and T2Hs (g). The white arrowhead points to the nucleus. h The largest PI fluorescence areas in T1Hs, T2Hs, and PCs. i Volumes of reconstructed three-dimensional nuclei in T1Hs, T2Hs, and PCs. In (d, e, h) and (i), violin outline width shows the density of the data; the thick bar represents the interquartile range (IQR) between the first and third quartiles, with the median marked by a white dot and labeled with the corresponding value; whiskers extend up to 1.5 times the IQR. ^**P < 0.01, ^***P < 0.001, n.s., not significant (two-sided Mann-Whitney U test). Source data are provided in Supplementary Data 5. j The development of T1Hs and T2Hs. The images below petals show the magnified views of the boxed regions containing T2Hs (dark blue). Pink and dark blue arrowheads point to the emerging T1H and T2H, respectively. For each stage, at least 3 petals were observed. k Expression profiles of key candidate genes across eight developmental stages of petals. Pink and dark blue bars indicate the stages when T1Hs and T2Hs arise, respectively. Source data are provided in Supplementary Data 6. l–o Results of mRNA in situ hybridization for NiinMYB5-1 (l), NiinGL3 (m), NiinGL2 (n), and NiinLMI1 (o) in N. integrifolia petals at different stages. All results are representative of at least two independently repeated experiments. See also Supplementary Fig. 14. Scale bars: (a left) 1 mm; (a right, b, c, f, g) 50 μm; (j, l–o) 100 μm. p A summary of gene expression patterns throughout petal development of N. integrifolia. The expression levels are determined based on the FPKM values and the intensities of in situ hybridization signals (the darker, the higher).