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First published online 17 August 2005
doi: 10.1242/dev.01969

Development 132, 4063-4074 (2005)
Published by The Company of Biologists 2005
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The gene ENHANCER OF PINOID controls cotyledon development in the Arabidopsis embryo

Birgit S. Treml1, Sabine Winderl1,*, Roman Radykewicz1,{dagger}, Markus Herz2, Günther Schweizer2, Peter Hutzler3, Erich Glawischnig1 and Ramón A. Torres Ruiz1,{ddagger}

1 Lehrstuhl für Genetik, Technische Universität München, Wissenschaftszentrum Weihenstephan, Am Hochanger 8, 85350 Freising, Germany
2 Bayerische Landesanstalt für Landwirtschaft, Institut für Pflanzenbau und -züchtung, IPZ 1b, Am Gereuth 2, 85354 Freising, Germany
3 Institut für Pathologie, GSF-Forschungszentrum für Umwelt und Gesundheit GmbH, 85764 Neuherberg, Germany



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  		Fig. 1. Comparison of wild-type and laterne seedlings. (A) Wild-type and (B) laterne seedling under scanning electron microscopy. Scale bars: 100 µm.

 


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  		Fig. 2. Semi-thin sections and SEM of laterne seedlings. (A-G) Longitudinal sections of laterne with emerging primary leaf primordium. (H-L) Cross-sections of laterne showing the apical cavity (arrow) harbouring small densely stained cells. (M-Q) SEM of different laterne seedlings. Generation of variable numbers of leaf primordia (arrowheads; N,O) with young trichomes (P,Q; black and white arrows, respectively). Scale bars: 100 µm in A-P; 10 µm in Q.

 


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  		Fig. 3. laterne embryo development. (A) Wild-type early heart stage (frontal view). (B-D) Wild-type heart stage series (lateral view). (C) Median optical section comparable to laterne (pid-15 enp) embryo in G. (E) Wild-type late heart stage. (F,G,K) laterne early, mid and late heart stage (K, lateral view). (H,I) A pid-15 embryo with three cotyledons (arrowhead points to third cotyledon). sp, shoot pole; co, cotyledon primordia; hy, hypocotyl; rp, root pole. Nomarski optics. Scale bars: 25 µm.

 


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  		Fig. 4. Adult and flower phenotypes of different enp pid combinations. Genotypes are indicated for adult plants (upper row) and their corresponding flowers or pin-ends (middle and bottom row). The pin-ends in the third row belong to plants of the two adjacent genotypes, as indicated by white arrows. The black arrow indicates a flowerless blind ending stem of pid-9 +/pid-9 +. The black arrowhead indicates flower structures on a stem of a pid-9 enp/pid-9 enp plant. White arrowheads refer to sepal fusions. Scale bars: 1 cm (upper row); 1 mm (middle and lower rows).

 


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  		Fig. 5. Development of flower organs in enp and pid combinations. Sepals (S), petals (P) and stamens (St) were scored. Mean values and standard deviations are given. Shaded regions indicate the occurrence of organ fusion (in % of all flowers examined; e.g. 98% fusion of sepals in pid-15 enp/+ enp). The pid homozygous plants developed variably reproductive gynoecia, whereas pid enp/pid enp double mutants led to collapsed gynoecia or completely lacked flowers. Wild-type, + +/+ enp, + enp/+ enp and pid-x +/+ enp plants did not display conspicuous infertility. The pid enp/+ enp plants exhibited partial fertility, while pid-x enp/pid-x enp plants were always sterile. *A second set of plants/flowers analysed. **Two stems carried terminal flowers.

 


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  		Fig. 6. PIN1:GFP localisation in laterne (pid-15 enp), wild-type and pid-15 embryos. (A-C) laterne, (D-F) wild type (G,H) and pinoid (all embryos between early and mid heart stage). Insets show higher magnifications; white arrows indicate PIN1:GFP cellular localisation. which is basal in A-C,G (right inset) and H (left inset), and apical in D-F,G (left inset) and H (right inset). Scale bars: 10 µm.

 


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  		Fig. 7. Auxin maxima in wild-type, pid-15 and laterne (pid-15 enp) embryos. (A-C,I) Wild-type embryos; (D-H) pinoid embryos; (K-M) laterne embryos. (A) Heart stage (arrowhead points to weak signal); (B,E-H,L,M) mid torpedo stage; (C) detail of B; (D) detail of E; (I) detail of B (reversed picture); (K) detail of L. Arrowheads indicate maxima. The arrow indicates the missing shoot maximum in F and a variable shoot maximum in L and M. co, cotyledon; rm, root meristem precursor. Scale bars: 20 µm.

 


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  		Fig. 8. Expression of STM, ANT and CUC2 in wild-type and laterne (pid-15 enp) embryos. (A,B,D,G,I,K,M,O,Q,R,T,U,W) Wild-type, (C,E,F,H,L,N,P,S,V,X) laterne, (A-H) STM expression, (I-P) ANT expression and (Q-X) CUC2 expression. (A-C,F,I-N,S,U,V,X) Arranged in series (top to bottom). (A,B) Cross-section series (top view) of globular stage (A) and heart stage embryo (B) with stripe-like domain of STM expression (arrowheads). (C) Cross section heart stage (top view). (D,E) Lateral views of wild-type (D) and laterne (E) heart stage embryos. (F) Tangential to median sections of young laterne torpedo stage (black arrowheads indicate patches of higher intensity). (G) Wild-type torpedo with STM expression defining the SAM. (H) Comparable picture of laterne torpedo, with patch-like pattern of STM signal. (I,K) Longitudinal series showing the ring-like ANT expression pattern in globular stage (I) and stained cotyledon primordia in heart stage (K). The black arrowheads in I and K indicate the central region lacking ANT. (L) Longitudinal series of laterne heart stage with ANT expression (arrowhead indicates emerging apical cavity without signal; arrows indicate emerging expression in vascular precursors). (M) Wild-type cross-section series with signal concentration in vascular precursors. (N) Cross-section series shows extension of ANT domain in apical pole of laterne, avoiding the centre (arrowhead). (O) Longitudinal section of wild-type torpedo (slightly out of centre; arrows as in L). Inset shows cotyledon cross-section. (P) Longitudinal section of laterne torpedo (arrowhead: apical cavity lacks ANT signal). Inset displays tangential cut to stress ring-shaped ANT expression. (Q,R) Globular (Q) and early heart stage (R) each with CUC2 expression. (S) laterne heart stage longitudinal series with distributed patches of expression (arrowheads). (T) Wild-type at late heart stage. (U) Wild-type cross-section series indicating the early stripe-like pattern. (V) A laterne cross-section (arrowheads: expression peaks); signal is also present in the centre. (W) Longitudinal section in torpedo embryo with lateral (ring-shaped) signals, avoiding the central SAM region (arrows). The inset is at a higher magnification. (X) Series of torpedo stage laterne with distributed expression (arrowhead). co, cotyledon; hy, hypocotyl; SAM, shoot apical meristem; vSAM, variable SAM. Scale bars: 20 µm.

 


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  		Fig. 9. WUS expression in wild-type and laterne (pid-15 enp/pid-15 enp) embryos. (A-C,E,G) Wild-type, (D,F,H) laterne. (A) WUS expression is found in L2 and L3 in wild-type globular stage. (B) Signal restricts to L3 in early heart stage (arrowhead). (C,D) Cross-section series of wild-type heart stage (C) and laterne torpedo stage (D), both with wild-type signal location. (E) Median section of the wild-type shows shoot apical pole and only part of one cotyledon (co) with WUS signal in L3. (F) Higher magnification of comparable laterne region exhibiting the same location in L3 (tissue layers L1-L3 indicated). (G,H) Longitudinal section of late torpedo stage wild-type (G) and laterne (H) with WUS signal. The inset (H) shows sense hybridisation. co, cotyledon; hy, hypocotyl. Scale bars: 20 µm.

 


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  		Fig. 10. Analysis of triple mutant pid-15 enp stm-5. (A,B) Seedling phenotype of triple (A) versus double (B) mutant (genotypes indicated). (C-E) Comparison of stm-5 (C), laterne (D) and wild-type (E) phenotype. Arrowheads and arrows respectively indicate shoot meristemless region between the cotyledons (C), trichomes of adult leaves (D) and trichomless cotyledons (E). Scale bars: 2.5 mm in A,B; 1 mm in C-E.

 


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  		Fig. 11. Auxin flux in the epidermis of the laterne apex. Arrows indicate direction of auxin transport as deduced from PIN1:GFP cellular position. (A) Apex of a laterne (pid-15 enp) embryo. (B) Apex of a wild-type embryo. Scale bars: 10 µm.

 




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