Fig. 1

H1 depletion relaxes the epigenetic control of several developmental and cellular transitions. 3h1 mutant plants show a relaxed control of seed dormancy (a), flowering time (b), lateral root formation (c), root hair density (d), root hair fate (e), stomatal spacing (f), and are impaired in callus production in vitro. 3h1 shows, compared to wild-type a prolonged dormancy, i.e., lower germination rate 1 day post-harvest but alleviated 3 weeks post-harvest, b early flowering measured by the number of rosette leaves at bolting (n = number of plants analyzed in this replicate; more experiment replicates are shown in Additional file 1: Figure S1), c increased number of lateral roots (eight DAG seedlings), d increased root hair density (scale bar, 200 μm), e occasional multi-cellular root hairs showing visible cell walls (arrows) in Renaissance staining (i, iii) compared to in wild-type and additional nuclei in DAPI counterstaining (ii: arrows, red; additional examples and comments are presented in Additional file 1: Figure S2; scale bar, 10 μm), f stomatal complexes with reduced spacing (adaxial cotyledon epidermis; see Additional file 1: Figure S2 for additional examples and quantifications; scale bar, 20 μm), and g decreased callus size produced from excised cotyledons in vitro (scale bar, 1 cm). Wild-type segregants (wt) were compared with triple mutant tissues/seedlings (3h1) and, whenever indicated, with complemented lines expressing H1.1 and H1.2 variants only (3h1; H1) or all three H1 variants (3h1; H1*). Statistical tests (a, b Welch t test; c Fisher exact test) were performed against wt replicates, ***p < 0.001; ns, not significant