Developmental Phenotypes of the teb Mutant.
(A) Ten-day-old seedlings of wild-type Col-0 (left) and teb-1 (right) plants. Bar = 2 cm.
(B) and (C) Root tips of Col-0 (B) and teb-1 (C) plants. Arrowheads indicate the bottom of differentiated cells with root hairs. Bars = 2 mm.
(D) and (E) Propidium iodide–stained root tips of Col-0 (D) and teb-1 (E) plants viewed by confocal laser scanning microscopy. Bars = 25 μm.
(F) and (G) Shoots of 20-d-old Col-0 (F) and teb-1 (G) plants. Bars = 1 cm.
(H) and (I) Stem of Col-0 (H) and fasciated stem of teb-1 (I). Bars = 1 cm.
(J) to (L) Toluidine blue–stained sections of the SAM from 8-d-old Col-0 (J) and teb-1 ([K] and [L]) plants. Bars = 100 μm.
(M) and (N) Higher magnification of the SAMs shown in (J) and (K), respectively. L1 and L2 layers are indicated in Col-0 (M), but the structure is disorganized in teb-1 (N).

Embryo Phenotypes of the teb Mutant.
Developing embryos of Col-0 ([A], [D], and [G]) and teb-1 ([B], [C], [E], [F], [H], and [I]).
(A) to (C) Sixteen-cell to early globular stage embryos.
(D) to (F) Mid to late globular stage embryos.
(G) to (I) Heart stage embryos. Insets show magnified views of hypophysis cell descendants.
Arrowheads in (C), (E), and (F) indicate abnormal cell division in the teb-1 embryo. Asterisks indicate lens-shaped cells or their descendents, which give rise to QC cells of the root. h, hypophysis; p, protoderm; s, suspensor. Bars = 25 μm.

Differentiation States in Roots of the teb Mutant.
(A) to (C) Lugol-stained root caps from Col-0 (A) and teb-1 ([B] and [C]) plants. Starch granules in columella root caps were stained dark purple.
(D) to (F) SCR:GFP expression in root tips of Col-0 (D) and teb-1 ([E] and [F]) plants.
(G) to (I) DR5:GUS expression in root tips of Col-0 (G) and teb-1 ([H] and [I]) plants.
Bars = 50 μm.

Molecular Characterization of the TEB Gene.
(A) Structure and mutant alleles of the TEB gene. Top, intron–exon structure of TEB and sites of mutation in the alleles. Rectangles represent exons. Black rectangles represent the coding region, and white rectangles represent 5′ and 3′ untranslated regions. Bottom, domain structure of the TEB protein. Predicted functional domains are indicated by dark gray boxes (helicase domain) and white boxes (DNA polymerase domain). The thick line below the intron–exon structure indicates the region covered by the cDNA clone in the cDNA library of the Kazusa DNA Research Institute.
(B) Structures of MUS308 and its homologs in higher eukaryotes. Dark gray rectangles represent helicase domains, and white rectangles represent DNA polymerase domains. Dotted lines separate the proteins into regions of highest conservation, with the least conserved region in the center and the N terminus. The percentage sequence identity between each pair is indicated in parentheses. A.t., Arabidopsis thaliana; D.m., Drosophila melanogaster; M.m., Mus musculus; H.s., Homo sapiens.
(C) RT-PCR analysis of TEB transcription in Col-0 and the teb-1 mutant. At left, fragment lengths of the size marker (SM) are indicated. The negative control lacking reverse transcriptase is indicated by –RT, and the reactions containing reverse transcriptase are indicated by +RT.
(D) and (E) Morphological phenotypes in root (D) and shoot (E) of the alleles for TEB. The marks in (D) indicate the tips of the roots.
(F) Real-time RT-PCR analysis of TEB and CycB1;1 gene expression in several organs. RNAs from flower buds (FB), flowers (Fl), stems (St), rosette leaves (RL), and roots (Ro) from 4-week-old Col-0 plants, 7-d-old seedlings (Se), and siliques (Si) were examined. Levels of 18S rRNA were used as a reference, and the values are expressed as ratios to the values in the flower buds. The values shown represent averages of three separate biological replicates ± sd.

DNA Damage in teb Mutants.
(A) and (B) Sensitivity of root growth to the DNA-damaging agents MMC (A) and MMS (B). Relative root elongation is the ratio of root elongation in medium containing the DNA-damaging agents to root elongation in control medium. Each point represents the average of the results from 40 to ∼60 plants, and error bars represent sd.
(C) Shoot phenotypes of Col-0, teb-1, and teb-3 on medium containing various concentrations of MMS.
(D) Real-time RT-PCR analysis of the expression of DSB-inducible genes in Col-0 and teb plants. The levels of 18S rRNA were used as a reference, and the values are expressed as ratios to the values in Col-0. The values shown represent averages of three separate biological replicates ± sd.

Intrachromosomal Recombination in the teb-1 Mutant.
(A) Structure of T-DNA pBI-F used to monitor homologous recombination events (). The top diagram shows the structure of the T-DNA region in pBI-F, and the bottom diagram shows the intact GUS gene reconstituted by intrachromosomal homologous recombination. Hyg^R, hygromycin resistance gene; LB, left border; RB, right border.
(B) Homologous recombination frequency determined by histochemical staining of leaves from 3-week-old plants. The graphs at left show the distribution of plants with the indicated number of GUS spots on leaves, and the graphs at right show the average number of GUS spots per individual plant. Two individual transgenic lines, F25 and F40, were tested in the wild-type backgrounds (TEB/TEB and TEB/teb-1) and the teb-1 background (teb-1/teb-1).

TGS in teb Mutants.
Semiquantitative RT-PCR analysis of TSI expression in the teb-1 and teb-3 mutants. Expression of TSI in Col-0 and fas1-1 plants was measured as negative and positive controls, respectively. Expression of the ACTIN2 gene was used as a reference.

Defective Cell Cycle Progression in the teb, tsk/mgo3/bru1, and fas2 Mutants.
(A) Mitotic index in the RAM of 5-d-old Col-0 and teb-1 seedlings. The mitotic index is the number of mitotic figures (metaphase, anaphase, and telophase cells) within 150 μm of the QC cells. The cortex and endodermis cell layer in one section of this region contains ∼80 cells in both Col-0 and teb-1 plants. Approximately 10 plants for each line were tested in one experiment. Error bars represent sd.
(B) to (M) Expression of cyclin-GUS in the RAM ([B] to [E]), young leaves ([F] to [I]), and the SAM ([J] to [M]) of Col-0 ([B], [D], [F], and [J]), teb-1 ([C], [G], and [K]), fas2-2 ([E], [H], and [L]), and tsk-3 ([I] and [M]) plants. Tissues from plants of the following ages were analyzed: RAM, 5 d old; young leaves, 14 d old; SAM, 7 d old.
(N) Real-time RT-PCR analysis of levels of mRNAs for cell cycle–regulated genes in Col-0 and teb-1 plants. The levels of 18S rRNA were used as a reference, and the values are expressed as ratios to the values in Col-0. The values shown represent averages of three separate biological replicates ± sd.