Dynamics of chromatin accessibility in Arabidopsis flower development. (A) Quantitative changes in DHSs between IM and day 2, 4, and 8 after flower induction for genomic regions detected as open chromatin at any time point and located nearby genes (3 kb upstream to 1 kb downstream of a gene). (B) K-means cluster analysis of differentially expressed genes. All the genes detected as differentially expressed (BH <0.05 and FC >1.8) in at least one time point comparison (IM vs. 2d, 2d vs. 4d, and 4d vs. 8d) are represented. (C) Percentage of genes in vicinity of AP1 or SEP3 and different classes of DHS, classified according to their expression change between days. Numbers above the bars show the total number of genes in the group. In all four cases there is a significant change of fractions across categories of DHS (χ2 test, P <0.001). (D) Confocal images of expression patterns of pGRF::GRF-GFP fusions in inflorescence meristems and during flower development. Expression patterns are summarized in schematic drawings on the right. Numbers indicate floral stage according to Smyth et al. , IM: inflorescence meristem, se: sepal, pe: petal, an: anther and ca: carpel. (E) Examples of TF gene loci that have DHSs with decreasing accessibility (top) and increasing accessibility (center) after flower induction. Genes involved in meristem identity like STM, BREVIPEDICELLUS (BP) and CAL show decreasing DHS peaks. On the other side, genes involved in flower organ initiation and determination like SEP3, PHV, and ALC show increased DHSs. In the bottom part of the figure are shown the accessibility profiles for AtGRF2, AtGRF5, and AtGRF8 loci are shown. DNase I hypersensitivity profiles at AtGRF2 and AtGRF5 loci do not change during time while an increase in accessibility is found for AtGRF8 locus between day 4 and 8.