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Abstract Detail

Growth and Vegetative Development

De Tullio, Mario C. [1], Jiang, Keni [2], Sanmartin, Maite [3], Kanellis, Angelos K. [4], Feldman, Lewis J. [2].

Constitutively expressed ascorbate oxidase transgene is silenced in roots of N. tabacum.

The establishment of the Angiosperm root apical meristem is dependent on the specification of a stem cell niche and the subsequent development of the quiescent center (QC) [1]. Auxin specifies stem cell niche formation by directly and indirectly affecting gene activities. Part of the indirect regulation by auxin may involve redox changes, favoring local, oxidized microenvironments. High ascorbate oxidase (AAO) activity is localized in QC cells [2], and is likely to be involved in the maintenance of QC cells in an undifferentiated state. Root development was analyzed in plants of N. tabacum constitutively expressing melon AAO under the 35S promoter [3]. No phenotype was observed in roots of transgenic plants, except for an average delay in germination of approximately 2 days. Surprisingly, the roots of AAO over-expressing transgenic tobacco lines exhibited no significant increase in AAO activity contradicting its 10-fold increase in leaves of the same plants. This data strongly suggests that selective expression of the AAO gene occurs in specialized root cells, possibly mediated by presently unknown silencing mechanisms. Analysis of the silencing mechanism is in progress, together with the characterization of an Arabidopsis line in which all 3 genes coding for AAO are knocked out.
[1] Jiang and Feldman, Annu Rev Cell. Dev. Biol. 2005, 21: 485-509
[2] Liso et al., J. Exp. Bot. 2004, 9999: 726-36
[3] Sanmartin et al., Planta 2003, 216:918-28

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1 - University of Bari, Plant Biology and Pathology, via Orabona 4, Bari, 70125, Italy
2 - UC Berkeley, Plant and Microbial Biology
3 - Centro Nacional de Biotecnología CSIC, Madrid, Spain, Genética Molecular de Plantas
4 - Aristotle University of Thessaloniki, Greece, Pharmaceutical Sciences

ascorbate oxidase
quiescent center
root development.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P26001
Abstract ID:32

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