Fruit development is actively restricted in the absence of fertilization in Arabidopsis
Adam Vivian-Smith1,2,
Ming Luo3,
Abdul Chaudhury3 and
Anna Koltunow2,*
1 Department of Plant Science, Waite Campus, University of Adelaide, P.M.B., 1 Glen Osmond, South Australia 5064, Australia
2 Commonwealth Scientific Industrial Research Organization, Plant Industry, Horticultural Research Unit, P.O. Box 350, Glen Osmond, South Australia 5064, Australia
3 Commonwealth Scientific Industrial Research Organization, Plant Industry, GPO Box 1600, Canberra, Australian Capital Territory 2601, Australia
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Fig. 1. Silique development in Arabidopsis. (A) Morphological features of the Arabidopsis pistil at anthesis. (B) An unpollinated senescing pistil. (C) Maturing seeded silique before dehiscence. Cells in the carpel that will compose the exocarp layer in the silique are coloured green, mesocarp is yellow, supportive sclerenchyma red and endocarp blue.
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Fig. 2. Features of the fwf mutant. (A) Comparisons of a pistil dissected from a anthesis stage Ler flower (a), Ler silique 7 days post-pollination (p), an emasculated unpollinated Ler pistil 7 day post-anthesis (up), compared with a parthenocarpic fwf silique in the Ler background (fwf up) and fwf in the near isogenic line (Col-1) following emasculation (NIL up). A valve has been removed from (a), (p) and (up fwf) to display the presence or absence of seeds. (B) Cleared siliques showing decreased seed set (arrowheads) in proximal region of the fwf silique following cross-pollination with Ler pollen. (C) Section of Ler ovule at anthesis. (D) Section from an unfertilized fwf ovule at anthesis. (E) Ler flower. (F) fwf flower. (G) ctr1-1 flower. (H) ein6 flower. (I-L) Lateral sections of carpel valves examined 7 days post-anthesis. (I) Unpollinated Ler. (J) Pollinated Ler. (K) Unpollinated fwf. (L) Pollinated fwf. (M-P) Transverse sections of carpel valves 7 days post anthesis. (M) Pollinated Ler. (N) Pollinated fwf. (O) Unpollinated fwf from flower below position 30, arrowhead indicates enlarged mesocarp cells. (P) Unpollinated fwf from flower above position 30. Abbreviations: endocarp (e) exocarp (x), mesocarp (m), sclerenchyma (s) and ovule (o). Scale bars: A, 3 mm; C,D, 30 µm; I-P, 50 µm.
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Fig. 3. Pistil receptivity and silique growth. (A) Receptivity period for Ler and fwf pistils examined by the removal of floral organs, except the pistil, at anthesis and controlled self-pollination on specific days after anthesis. (B) The relationship of floral position on the primary inflorescence meristem and final parthenocarpic silique length in male sterile pop1 (circles) and pop1 fwf (squares), emasculated fwf (diamonds) and male sterile pop1 ats fwf triple mutant (triangles). (C) Silique growth of pollinated Ler (Ler p), emasculated fwf and male sterile pop1 ats fwf compared to emasculated and unfertilized Ler (Ler up).
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Fig. 4. Map positions for fwf, bel1-1 and ats on chromosome 5.
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Fig. 5. Comparison of silique length and morphology in various mutant backgrounds, 7 days post-anthesis. (A) Unpollinated Ler pistil (up), pollination-induced Ler silique (p) and fwf parthenocarpic silique. (B) ful-7 and ful-7 fwf double mutants following pollination (p) or emasculation (up) in ful-7 fwf. The inset labeled ‘p’ shows continued replum development and replum cell expansion (arrow) in pollinated ful-7. The inset marked ‘up’ shows the absence of continued replum growth in emasculated and unpollinated ful-7 fwf pistils. (C) Silique development in the gai-1 background. (D) Silique development when fwf is combined with gai-1 and ats. (E-I) Sections of silique tissues 7 days post-anthesis. (E) Unpollinated gai-1. (F) Parthenocarpic gai-1 fwf. (G) Pollinated gai-1 fwf. (H) Parthenocarpic pop1 ats fwf with increased mesocarp cell division. (I) Parthenocarpic gai-1 ats fwf where ats restores anticlinal mesocarp cell division. Mesocarp cells adjacent to vascular bundles remain enlarged (arrowhead). Abbreviations as for figure 2. Scale bars: A-D, 3 mm; E-I, 50 µm.
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Fig. 6. A model for the regulation of silique development in Arabidopsis by auxin- and GA-mediated signal transduction, FWF and fertilization-dependent processes. FWF* indicates areas where normal FWF activity acts to modulate these developmental processes in a repressive manner.
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© The Company of Biologists Ltd 2001
