Figure 2.

Ectopic Nondegradable Cyclin B1 Expression Affects N. tabacum Seedling Development.

(A) and (C) Appearance of 20-d-old seedlings germinated on plant agar deriving from lines CycBMut6-I. C, cotyledon; L, leaf.

(B), (D), and (E) Environmental scanning electron micrographs showing abnormalities in cotyledon of weakly affected offsprings from line CycB1Mut6-I (B) and in the epidermal cell layer of a bulging hypocotyl of severely affected 10-d-old offspring from line CycB1Mut6-I (D) compared with a normal growing pBI:GUS transgenic N. tabacum seedling (E).

(F) and (G) Longitudinal sections through a paraffin-embedded seedling from line CycB1Mut6-III (F), which has a similar phenotype like that shown in (C) and from the pBI:GUS transgenic control line (G). LP, leaf primordial; SAM, shoot apical meristem; VT, vascular tissue.

(H) to (O) Sections of seedlings deriving from line CycB1Mut6-I, which are similar to that shown in (C) (see [H], [J], [L], and [N]), and of a transgenic control seedling harboring a pBI:GUS construct (see [I], [K], [M], and [O]). Young leaves ([H] and [I]), petioles ([J] and [K]), hypocotyls ([L] and [M]), and roots ([N] and [O]) are shown.

(P) and (Q) Histograms of the DNA distribution in CycB1Mut6-I transgenic T2 seedlings 20 d after germination (P) compared with the pBI:GUS transgenic N. tabacum seedling from the same age (Q). Percentage of cell cycle distribution of the nuclei is mentioned below. Bars = 100 μM in (B) and (D) to (G), and 200 μM in (H) to (O).