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Development 129, 4291-4300 (2002)
© 2002 The Company of Biologists Limited

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

Sureshkumar Balasubramanian* and Kay Schneitz{dagger},{ddagger}

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
{dagger} Present address: Entwicklungsbiologie der Pflanzen, Wissenschaftszentrum Weihenstephan, Technische Universität München, Am Hochanger 4, 85354 Freising, Germany

{ddagger}Author for correspondence (e-mail: schneitz{at}wzw.tum.de)

Accepted 1 July 2002

The ovules of Arabidopsis show polarity along the proximal-distal and the adaxial-abaxial axis. NOZZLE, a gene that encodes a novel protein and BELL1, encoding a homeodomain protein, play a vital role in pattern formation along the proximal-distal axis. INNER NO OUTER, which encodes a member of the YABBY family of transcription factors and SUPERMAN, encoding a zinc finger transcription factor, are essential for the establishment and maintenance of adaxial-abaxial polarity. To date, the co-ordination of patterning along these two axes is unclear. Here we show that NOZZLE plays a vital role in pattern formation along the adaxial-abaxial axis as well. We investigated the expression of INNER NO OUTER in various mutant backgrounds and have identified ABERRANT TESTA SHAPE and NOZZLE as spatial regulators of INNER NO OUTER expression. In addition, we show that NOZZLE and AINTEGUMENTA, which encodes an AP2 domain transcription factor, regulate the temporal expression of INNER NO OUTER and that BELL1 is essential for INNER NO OUTER expression. We further analysed the expression of BELL1 and AINTEGUMENTA in inner no outer mutants and show that the positive auto-regulatory control of INNER NO OUTER expression involves AINTEGUMENTA. Based on our results we propose a model for adaxial-abaxial pattern formation during ovule development. Our results indicate that NOZZLE plays a central role in patterning both the proximal-distal and the adaxial-abaxial axes. Furthermore, negatively regulating INO expression in a temporal manner, ensures that the adaxial-abaxial polarity is established after the specification of the chalaza, a proximal-distal axis pattern element. It therefore serves as a molecular link between these processes during ovule development in Arabidopsis thaliana.

Key words: Ovule development, Pattern formation, Organogenesis, Arabidopsis thaliana, NOZZLE, INNER NO OUTER






© The Company of Biologists Ltd 2002