QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Balasubramanian, S. Articles by Schneitz, K. Search for Related Content PubMed PubMed Citation Articles by Balasubramanian, S. Articles by Schneitz, K.

NOZZLE links proximal-distal and adaxial-abaxial pattern formation during ovule development in Arabidopsis thaliana

Sureshkumar Balasubramanian^* and Kay Schneitz^,

Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008, Zurich, Switzerland
^* Present address: Max-Planck Institut für Entwicklungsbiologie, Spemannstrasse 35, D-72076, Tübingen, Germany
Present address: Entwicklungsbiologie der Pflanzen, Wissenschaftszentrum Weihenstephan, Technische Universität München, Am Hochanger 4, 85354 Freising, Germany

View larger version (186K): [in a new window]   Fig. 1. Ovule development in wild type (A-D), nzz-2 (E-H), ats (I-L), nzz-2 ats (M-P) and sup-5 (Q-T). Stages: (A,E,I,M) 2-I; (B,F,J,N,Q) 2-III; (R) 2-IV; (C,G,K,O,S) 3-IV; (D,H,L,P,T) 4-IV. The outer integument initiates earlier than the inner integument and is visible before the inner integument in nzz-2 (arrow in F). Adaxial growth of the outer integument can be seen in nzz ats (arrows in O and P). Abaxial initiation of the outer integument (arrows in Q and R) and the abnormal growth (arrows S and T) on the adaxial side can be seen in sup-5. nu, nucellus; ii, inner integument; oi, outer integument; fu, funiculus; mp, micropile; pt, pollen tube; ad, adaxial; ab, abaxial. Scale bars: 20 µm.

View larger version (222K): [in a new window]   Fig. 2. Expression pattern of INO during ovule development in wild type (A-D), ant-72F5 (E-H), ino-2 (I-L) and bel1-1460 (M-O). P is a control section hybridised with the sense probe of INO. Stages: (A,E,I,M) 1-I/II; (B,J,N,P) 2-I; (F) 2-II; (C,D,K) 2-III; (O) 2-IV; (G,L) 3-I; (H) 4-V. ant mutants were staged on the basis of their ovule, carpel and anther developmental profile relative to each other. INO expression can be detected in cells that give rise to the outer integument in wild type. The cell that undergoes a division to form two cell layers and the triangular tip cell does not express INO (arrow in C). Note the absence of INO expression in the adaxial cell layer (arrow in D). Note the absence of INO expression even at the site of outer integument initiation in ant-72F5 (arrow in G). INO expression can be detected at late stages (H,b) but only in a few epidermal cells, similar to the early stages in wild type. The typical horseshoe appearance is not present (arrow H,a). No INO expression can be detected in ino-2 (I-L) and bel1-1460 (M-O). Arrows in L indicate site of outer integument initiation in wild type. Arrows in O denote early chalazal bulges in bel1-1460. Sense probe gave no signals above background (P). Scale bars: 20 µm.

View larger version (166K): [in a new window]   Fig. 3. Expression pattern of INO during ovule development in nzz-2 (A-D), ats (E,F), sup-5 (G,H) and nzz-2 ats (I-L). Stages: (A,G,I) 1-II/2-I; (B,E,H,J) 2-III; (C) 2-IV; (D,F,K) 3-I; (L) 3-IV. INO expression remains unaltered in nzz-2 except that it might be shifted distally by few cells as observed by the shifting of the outer integument (A-D). The tip cell does not show INO expression as in wild type (B arrow). The absence of INO expression at the adaxial side can be seen in ats mutants (arrow in E). The tip cell and the adaxial cell layer of the outer integument do not show INO expression in ats mutants (arrow in F). In sup-5 early onset of INO expression is similar to wild type (arrow in G), but around stage 2-III, INO expression can be detected throughout the central region (arrow in H). In ovules of nzz-2 ats mutants, INO expression is similar to wild type in most instances (arrow in I,a), but sometimes the expression can be seen throughout the central region (arrow in I,b). Instead of a ‘horseshoe appearance’ a complete ring can be observed in a cross section through the central region of a nzz-2 ats double mutant (arrow in L,a). Scale bars: 20 µm.

View larger version (219K): [in a new window]   Fig. 4. Expression of BEL1 and ANT in ino-2, nzz-2 ino-2. (A-D) BEL1 expression in ino-2. (E-H) ANT expression in ino-2. (I-L) ANT expression in nzz-2 ino-2. (M,N) ANT expression in nzz-2. (O) ANT expression in bel1-1460. (P) BEL1 expression in ant-72F5. Stages: (E,I) 1-I/II; (A,F,J,M) 2-I; (B,G,N) 2-II; (C,K) 2-III; (D,H,O,P) 2-IV; (L) 3-IV. Note the presence of BEL1 expression at the site of outer integument initiation in ino-2 (arrows in B, C and D). Around stage 2-IV, an absence of ANT expression can be observed at the site of outer integument initiation in ino-2 (arrows in H). No strong spot of ANT expression can be detected in nzz-2 ino-2 (arrow in K). Note the presence of BEL1 expression in ant-72F5 (P, arrow) and ANT expression in bel1-1460 (O, arrow). Scale bars: 20 µm.

View larger version (8K): [in a new window]   Fig. 5. A genetic model for adaxial-abaxial pattern formation and outer integument development during ovule development in Arabidopsis thaliana. (A). Initiation of INO expression. ANT and NZZ act antagonistically and are needed for the correct timing of the onset of INO expression. BEL1 is a pre-requisite for INO expression. (B) Feedback regulation of INO expression. After initiation, INO positively regulates ANT expression, which in turn leads to positive regulation of INO and NZZ expression. NZZ in turn forms a negative feedback on ANT thereby maintaining the levels of ANT and INO expression. (C) Spatial regulation of INO expression. The dashed lines with a question mark indicate that the interaction between NZZ, ATS and SUP is unclear. Lines with arrows indicate activation of transcription. Lines with barred ends represent an inhibitory input.