Figure 2.

The Organization of Chromatin States on Chromosomes and within Nuclei.

(A) Oe. elata ssp hookeri strain hookeri de Vries. Giemsa C-banding; arrowheads indicate C-band-positive NOR-heterochromatin.

(B) Oe. elata ssp hookeri strain hookeri de Vries. Sequential C-banding/DAPI (top) and FISH with 45S rDNA (green) and 5S rDNA (red, arrowed) probes (bottom) on early metaphase chromosomes. Note that the subtelomeric regions are still slightly diffuse; arrowheads indicate NOR-heterochromatin.

(C) Oe. villosa ssp villosa strain bauri Standard. C-banding/DAPI on late metaphase chromosomes; arrowheads indicate NOR-heterochromatin.

(D) Oe. biennis strain suaveolens Grado. Immunodetection of H3K9me2 (top, red) and DAPI-stained chromosomes (bottom).

(E) and (F) Oe. elata ssp hookeri strain johansen Standard. On metaphase chromosomes, euchromatin indexed by H3K4me2 (E) or H3K27me3 (F) occupies small distal regions, that is, satellites and segments comparable in size to satellites (merged images, red signals). Arrowheads indicate satellites; arrows indicate regions where NOR-heterochromatin is located.

(G) Oe. biennis strain suaveolens Standard. A fragment of DAPI-stained early prophase from root tip, disturbed by strong squashing. The relative position of centromere-containing early-condensing chromatin blocks (not marked), NOR-heterochromatin blocks (arrows, three of them are marked), and terminal heterochromatin (arrowheads, only two of them are marked) is clearly visible.

(H) to (J) Oe. elata ssp hookeri strain johansen Standard. Distribution of H3K4me2 (H) and H3K27me3 ([I] and [J]) on prophase chromosomes ([H] and [I]) or early metaphase chromosome (J). Until late metaphase, the late-condensing chromatin in Oenothera is not fully condensed. Top, DAPI images; bottom, immunosignals (red) merged with DAPI (blue). Arrowheads indicate DAPI-positive terminal heterochromatin.

(K) and (L) Oe. glazioviana strain r/r-lamarckiana Sweden. Immunodetection of H3K27me2 (red, merged images).

(K) Metaphase plate with H3K27me2-enriched chromosome termini.

(L) DAPI-bright terminal heterochromatin (DAPI staining, blue, top) strictly colocalizes with H3K27me2 immunosignals (red, merged, bottom).

(M) Oe. biennis strain suaveolens Grado. A metaphase chromosome (left, DAPI staining) with secondary constriction and its H3K27me2 pattern (right). Arrowhead indicates the satellite; arrow indicate region where NOR-heterochromatin is located.

(N) Oe. elata ssp hookeri strain hookeri de Vries. Nuclei stained with DAPI (left and right) or CMA₃ (middle) with facultative chromocenters and minute blocks of terminal heterochromatin (arrowed in [M], left).

(O) Oe. biennis strain suaveolens Grado. Nucleus with facultative chromocenters (DAPI staining, top) that are negative for H3K4me2 (red, bottom).

(P) Oe. elata ssp hookeri strain johansen Standard. In the nuclei of mature parenchyma, facultative chromocenters are lacking (DAPI staining, top). DAPI-bright terminal heterochromatin is also detectable as spots enriched in H3K27me2 (red, bottom).

(Q) Oe. elata ssp hookeri strain hookeri de Vries. In nuclei from root epidermis, chromocenters are partially decondensed.

(R) Graphical interpretation of how the main chromatin states are organized in cycling nuclei (top), noncycling nuclei deprived of the facultative chromocenters (middle), and noncycling nuclei with facultative chromocenters partially decondensed (bottom). Polarization of nuclear architecture and NOR-heterochromatin were not included in the graphical interpretations.

Bars = 5 μm.