PMC

Schematic diagram of the Arath;CDC25 gene (to scale) with exons (encoding the C-terminal catalytic domain), introns and 3′- and 5′-UTRs, as indicated. The relative positions of the two arath;cdc25 insertions are shown.

Expression of Arath;CDC25 in insertion and over-expression lines: (A) expression of Arath;CDC25 in Arath;CDC25^oe line 18 and WT is absent in SALK and GABI-Kat with primers for the full-length gene Atcdc25F and Atcdc25R; (B) Arath;CDC25 transcript level as a percentage of maximum in the over-expressing lines, Arath;CDC25^oe (18 and 22) compared with WT (±s.e.) with primers Atcdc25F and Atcdc25R (n = 3).

Transcript levels of Arath;CDC25 in seedlings challenged with HU. Mean (±s.e.) percentage of maximum transcript level of Arath;CDC25 in WT plants grown for 10 d in M&S medium, without HU (0) or with 1 or 2 mm HU. The tool used was semi-quantitative RT-PCR and transcript levels were normalized as percentage of maximum (n = 3).

All genotypes are equally sensitive to zeocin. (A and B) WT, Arath;CDC25^oe lines 18 and 22, arath;cdc25 SALK and GABI-Kat T-DNA insertion seedlings grown on M&S medium supplemented with (A) 10 µm zeocin for 10 d (scale bar = 1 mm) or (B) 50 µm zeocin for 10 d. (C) Mean primary root length (±s.e.) of 10-d-old arabidopsis seedlings (n = 16). Levels of significance (P) are indicated by Student's t-test (*** < 0·001).

Similar root growth of lines in which Arath;CDC25 expression has been perturbed: (A) WT, Arath;CDC25^oe 18 and 22, arath;cdc25 T-DNA insertion SALK and GABI-Kat seedlings grown on M&S medium, in a vertical position, for 10 d (scale bar = 1 mm); (B) mean (± s.e.) of the sum of lateral root (LR) and lateral root primordia (LRP) (±s.e.) as a function of the mean (±s.e.) primary root length for WT, Arath;CDC25^oe lines 18 and 22, arath;cdc25 T-DNA SALK and GABI-Kat lines (n = 20). Rates of lateral root initiation per millimetre primary root (y divided by x) are mean (±s.e.): WT, 0·21 ± 0·04; SALK, 0·21 ± 0 .09; GABI, 0·15 ± 0·06; Arath;CDC25^oe #18, 0·18 ± 0·03; Arath;CDC25^oe #22, 0·27 ± 0·06.

All genotypes are equally sensitive to 50 mm NaCl. (A) Effect of increasing NaCL concentration (mm) on mean (±s.e.) on root length of 20-d-old WT seedlings grown on M&S medium. LD₅₀ (arrow) (n = 20). Primary root growth LD₅₀ (arrow) for WT at increasing NaCl molarities for 20 d (n = 20). (B) Mean number of lateral roots (LR) and lateral root primordia (LRP) as a function of mean ± s.e.r primary root length in the 10-d-old seedlings supplemented with 0 (closed symbols) or 50 mm (open symbols) NaCl (n = 20). Mean (±s.e.) rate of lateral root initiation per millimetre of primary root of control: WT, 0·22 ± 0·03; GABI, 0·31 ± 0·04; Arath;CDC25^oe #18 (0·22 ± 0·03); and with 50 mm NaCl: WT, 0·03; GABI, 0·11; Arath;CDC25^oe #18, 0·09.

(A, B) Differential root growth on HU of lines in which Arath;cdc25 expression has been perturbed. Root phenotype of arabidopsis 35S::Arath;CDC25^oe over-expressing lines, arath;cdc25 T-DNA lines and WT treated with (A) 1 mm or (B) 2 mm HU for 10 d (scale bar = 1 mm). (C, D) Mean number of lateral roots (LR) and lateral root primordia (LRP) as a function of mean ± s.e. primary root length in 10-d-old seedlings grown on M&S medium supplemented with (C) 1 mm or (D) 2 mm HU (n = 20). Mean (±s.e.) rate of lateral root initiation per millimetre of primary root for 1 mm HU: WT, 0·10 ± 0·01; GABI, 0·15 ± 0·02; SALK, 0·19 ± 0·02; #18, 0·25 ± 0·03; #22, 0·22 ±0·01; and for 2 mm HU: WT, 0·11 ± 0·01; GABI, 0·12 ± 0·01; SALK, 0·10 ± 0·01; #18, 0·26 ± 0·01; #22, 0·26 ± 0·01.

T-DNA insertion lines hypersensitive to 1 mm HU over a 17-d period. Top panel: seedling phenotypes (scale bar = 10 mm). (A–D) Primary root length as a function of time after the start of germination (days). Linear regressions (P < 0·001 in all cases) are given for each of the genotypes perturbed in Arath;CDC25 expression (open symbols, dashed lines), compared with WT (closed symbols, continuous line). The regression equations are as follows. WT: y = 2·69x – 5·68; Arath;CDC25^oe line 22: y = 3·17x – 7·99; Arath;CDC25^oe line 18: y =3·38x – 9·5; arath;cdc25 GABI-Kat: y = 2·11x – 4·58; arath;cdc25 SALK y = 2·26x – 5·01. (E) Mean number of lateral roots (LR) and lateral root primordia (LRP) as a function of mean ± s.e. primary root length (n = 20). Mean (± s.e.) rate of lateral root initiation per millimetre of primary root: WT, 0·49 ± 0·06; GABI, 0·43 ± 0·06; SALK, 0·40 ± 0·05; #18, 0·76 ± 0·05; #22, 0·64 ± 0·09.