Article Figures & Data
Figures
- Fig. 1.
Top and middle, Silique elongation of emasculated anthesis pistils after pollination (P), without pollination (UP), or treated with GA3 (10 μmol pistil−1), NAA (10 μmol pistil−1), or BA (1 μmol pistil−1) in the Ler (top) and Col-1 (middle) ecotypes. Bottom, Silique elongation in the gai background after emasculation of anthesis-stage pistils left unpollinated (UP) or after cross-pollination (P) or NAA treatment (10 μmol pistil−1). For estimates of error (±sd) refer to Table I.
- Fig. 2.
Siliques 7 DPA after treatment with IAA, NAA, GA3, or BA in the Ler background (top) or Columbia (bottom), with respective application levels in micromoles per pistil indicated in each panel. UP, Unpollinated; P, pollinated.
- Fig. 3.
Receptivity period for pollination- and GA3-induced silique elongation was determined by a single treatment of either GA3 (▴; 10 μmol pistil−1) or pollination (●) to emasculated pistils of Arabidopsis at various DPA in the Ler (top) and Col-1 (middle) ecotypes. Seed set (bottom) was also determined with respect to the DPA following pollination in Ler (black bars) and Col-1 (hatched bars).
- Fig. 4.
Ws-O siliques pollinated (P), unpollinated (UP), and GA3 treated (10 μmol pistil−1) compared with spy-4 unpollinated (UP), pollinated (P), and GA3-, NAA-, or BA-treated (10, 10, and 1 μmol pistil−1, respectively; top) siliques. gaiand ga5-1 unpollinated pistils and pollinated siliques (Ler; bottom) compared with GA3, NAA, and BA treatment (10, 10, and 1 μmol pistil−1, respectively), as described in “Materials and Methods.”
- Fig. 5.
Carpel wall cross-sections illustrating the degree of carpel expansion and development from an anthesis-stage pistil compared with 7-DPA unpollinated, pollinated, and PGR-treated siliques from the gai and Ler backgrounds. a, Anthesis-stage Ler pistil; b, unpollinated Ler pistil; c, pollinated Ler silique; d, Ler silique induced with 10 μmol GA3 pistil−1; e, Ler silique induced with 10 μmol NAA pistil−1; f, pollinatedgai silique. Unmarked arrowheads indicate dehiscence zones; X, exocarp; M, mesocarp; T, supportive sclerenchyma; N, endocarp; S, seed; O, ovule; P, septum; F, funiculus; R, replum. Scale bar = 250 μm.
- Fig. 6.
Longitudinal carpel wall sections of Ler at anthesis (a) and at 7 DPA for an unpollinated silique (b), a pollinated silique (c), and parthenocarpic siliques induced by 10 μmol GA3 pistil−1(d), 1 μmol BA pistil−1 (e), 10 μmol NAA pistil−1 (f). g to l, Silique wall sections of the respective Ler treatments in the gaibackground. Carpel wall sections of spy-4 anthesis pistil (m) and 7 at DPA for an unpollinated pistil (n), pollinated silique (o), and emasculated spy-4 pistil induced to grow with 10 μmol GA3 pistil−1(p). Rescue of carpel wall structure in thega5-1 biosynthetic mutant, 7-d pollinatedga5-1 silique (q), ga5-1parthenocarpic silique induced with 10 μmol GA3pistil−1 (r). X, Exocarp; M, mesocarp; T, supportive sclerenchyma; E, endocarp; O, ovule; F, funiculus. Scale bar = 100 μm.
- Fig. 7.
A model suggesting how GA biosynthesis and perception may determine silique structure in Arabidopsis. Signals from fertilization allow cell division, cell expansion, and differentiation during development. This may include activation of certain steps within the GA signal transduction cascade required for normal differentiation. Levels of active GAs (GA1, GA3, or GA4) would specifically limit cell division and the biosynthetic mutants (italics) would block or alter this process. One exception occurs at GA4, where other known 3β-hydrolyases may allow synthesis of active GAs. Based on mutant analysis described here, GAI may participate in GA perception by transducing signals that regulate cell division. a, At high GA levels cell differentiation occurs as for normal pollinated siliques; b, at low levels of active GA an auxin-like effect dominates with limited cellular division; and c, at very low levels of GA pistils cannot differentiate into siliques. The steps in GA biosynthesis between ent-copalyl diphosphate and GA19 or GA24 are abbreviated for simplicity. Other steps are detailed in Hedden and Kamiya (1997) and Sponsel et al. (1997). X, Exocarp; M, mesocarp; E, endocarp.
Tables
Stage and Treatment Ecotype/Mutant Ler LER Col-1er2 Col-1 Ws-O spy-4 gai1-a ga5-1 mm Anthesis pistils 2.8 ± 0.2 3.2 ± 0.2 2.9 ± 0.3 3.2 ± 0.4 3.2 ± 0.2 2.8 ± 0.3 2.9 ± 0.3 3.2 ± 0.3 Emasculated without pollination 4.1 ± 0.4b 4.8 ± 0.4a 3.7 ± 0.2c 4.1 ± 0.3b 4.5 ± 0.1ab 4.9 ± 0.4a 4.5 ± 0.4a 5.0 ± 0.2a Emasculated with pollination 11.5 ± 1.0c (6.7) 16.7 ± 1.5a (8.3) 11.3 ± 0.6c (10.6) 16.0 ± 1.7a (15.3) 17.3 ± 1.1a (10.6) 14.6 ± 0.8b (5.7) 9.5 ± 1.2d (4.1) 10.5 ± 1.0cd (4.2) IAA, 10 μmol pistil−1 7.5 ± 0.9 (3.7) 7.9 ± 2.4 (2.9) 6.9 ± 0.7 (5.0) 5.2 ± 0.4 (2.3) NAA, 10 μmol pistil−1 6.8 ± 0.8 (3.1) 8.9 ± 3.5 (3.6) 4.0 ± 1.7ns (1.4)1-b 5.9 ± 1.4 (3.2) 8.7 ± 1.4 (2.8) 7.6 ± 1.2 (2.9) BA, 0.1 μmol pistil−1 5.9 ± 0.8 (2.4) 7.9 ± 0.5 (2.9) 5.3 ± 0.6 (3.0) 4.5 ± 1.3ns (1.5)1-b BA, 1 μmol pistil−1 5.7 ± 0.4 (2.2) 6.2 ± 1.1 (1.9)1-b 2.9 ± 0.3ns (0)1-b 5.1 ± 0.7 (2.2) 5.4 ± 1.1ns (1.3)1-b 6.1 ± 0.2 (2.0) GA3, 0.1 μmol pistil−1 8.2 ± 0.8 (4.2) 11.0 ± 3.2 (4.8) 5.9 ± 0.9 (3.8) 7.4 ± 0.4 (4.9) GA3, 1 μmol pistil−1 9.5 ± 1.5 (5.2) 12.2 ± 1.6 (5.6) 7.6 ± 0.2 (6.0) 9.2 ± 1.1 (7.2) GA3, 10 μmol pistil−1 10.0 ± 1.1 (5.6) 14.5 ± 1.9 (7.0) 9.2 ± 0.5 (7.9) 10.6 ± 1.4 (8.9) 9.8 ± 0.8 (4.9) 8.4 ± 1.1 (2.7) 5.3 ± 0.7 (1.5)1-b 10.0 ± 1.1 (3.9) Results are means ± sd. Numbers in parentheses represent the fold increase in silique length as described in “Results.” ns indicates that the mean silique lengths are not significantly different from unpollinated pistils harvested at 7 DPA.
- Table II.
Comparison of cell number in cross-sections of different Arabidopsis carpels at anthesis and 7 DPA
Treatment DPA Carpel Cell No. per Tissue Type Exocarp Mesocarp Endocarp Anthesis 0 81 ± 18.5 177 ± 5.0 25.3 ± 5.0 Ler unpollinated 7 82 ± 10.6 171 ± 33 28.0 ± 8.7 Ler + pollination 7 79 ± 10.6 167 ± 7.0 32.7 ± 12.2 Ler + 10 μmol−1 pistil GA3 7 69 ± 2.3 154 ± 6.9 23.3 ± 4.2 Ler + 10 μmol−1 pistil NAA 7 67 ± 8.1 180 ± 17.8 24.0 ± 6.9 gai + pollination 7 67 ± 11.7 149 ± 7.6 20.7 ± 1.2 ga5-1 + pollination 7 67 ± 10.0 131 ± 18.1 20.0 ± 4.3 Results are means ± sd.
- Table III.
Comparison of the mean cell length, normal to the silique elongation axis, in Arabidopsis carpel tissue layers from anthesis and 7-DPA pollinated or PGR-treated pistils
Stage of Silique Development and Treatment Type Tissue Anthesis (2.8 ± 0.2) LerUP3-a (4.1 ± 0.4) Ler+P3-b (11.5 ± 1.0) Ler+GA33-c (10.0 ± 1.1) Ler+NAA3-d (6.8 ± 0.8) gai+P3-b (9.5 ± 1.2) ga5-1+P3-b (10.5 ± 1.0) ga5-1+GA33-c (10.0 ± 1.1) μm Exocarp 15 ± 8 28 ± 15 49 ± 32 82 ± 48 59 ± 24 46 ± 41 67 ± 42 60 ± 33 Mesocarp 1 10 ± 4 11 ± 4 13 ± 5 13 ± 3 16 ± 6 20 ± 6 19 ± 5 20 ± 6 Mesocarp 2 11 ± 3 11 ± 3 12 ± 3 17 ± 4 13 ± 5 20 ± 6 23 ± 6 18 ± 7 Mesocarp 3 11 ± 4 14 ± 5 21 ± 8 17 ± 7 17 ± 6 29 ± 10 26 ± 8 30 ± 10 Endocarp 7 ± 2 13 ± 3 22 ± 6 20 ± 7 20 ± 7 28 ± 7 28 ± 8 24 ± 8 - Table IV.
Comparison of the mean cell number, in longitudinal sections of Arabidopsis carpel tissues from anthesis and 7-DPA pollinated or PGR-treated pistils
Stage of Silique Development and Treatment Type Tissue Anthesis (2.8 ± 0.2) Ler UP4-a (4.1 ± 0.4) Ler +P4-b (11.5 ± 1.0) Ler +GA34-c (10.0 ± 1.1) Ler +NAA4-d (6.8 ± 0.8) gai +P4-b (9.5 ± 1.2) ga5-1 +P4-b (10.5 ± 1.0) ga5-1 +GA34-c (10.0 ± 1.1) Exocarp 227 ± 20 196 ± 23 277 ± 26 176 ± 38 133 ± 13 241 ± 33 223 ± 26 232 ± 29 Mesocarp 1 315 ± 17 396 ± 15 951 ± 41 788 ± 28 494 ± 25 440 ± 28 609 ± 18 567 ± 35 Mesocarp 2 287 ± 12 389 ± 11 983 ± 34 642 ± 24 601 ± 28 437 ± 23 489 ± 14 623 ± 21 Mesocarp 3 289 ± 19 326 ± 17 617 ± 30 664 ± 34 493 ± 22 306 ± 13 446 ± 16 440 ± 20 Endocarp 420 ± 19 351 ± 14 556 ± 28 560 ± 25 420 ± 35 303 ± 16 415 ± 18 450 ± 20
