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Abstract Detail

Growth and Vegetative Development

Ilegems, Michael [1], Rusconi, Saul [2], Meylan-Bettex, Marlyse [2], Bowman, John [3], Stieger, Pia [2].

Auxin, KANADI1 and class III HD-ZIP transcription factors in vascular tissue differentiation.

In a first phase of vascular differentiation, defined cells are recruited within a growing organ to form continuous files – the procambium. In the second phase, cells deriving from the procambium differentiate into xylem, phloem and fibers. The conducting functions of vascular tissues require perfect cell alignment and tissue continuity, transverse patterning within veins, as well as proper integration within the non-vascular tissues. The plant hormone auxin plays a primary role in procambium cell recruitment. Early markers of cambium and xylem precursor cells are class III HD-ZIP transcription factors. They antagonize the expression of KANADI genes, which are expressed in phloem precursor cells. The aim of this study was to analyze direct relationships between these diverse regulatory mechanisms in vein patterning.
To this end we expressed KANADI1 under the control of the class III HD-ZIP ATHB15, in order to reduce class III HD-ZIP contents in provascular cells.
Ectopic expression of KAN1 in provascular cells and the shoot apical meristem inhibited the establishment of a bilateral axis during embryogenesis. Furthermore seedlings developed a thicker and shortened hypocotyl, had severely reduced root growth, a variable number of cotyledons, a reduced shoot apical meristem and no vascular system. Ectopic expression of KANADI1 had negative effects on class III HD-ZIP gene expression only late in embryogenesis. In contrast, correct localization of the auxin efflux facilitator PIN1 was inhibited at heart stage, when preprocambium cell recruitment normally occurs. Our results propose auxin flow along cell files being the first step in vascular development and KANADI1 being a negative regulator of PIN1 activity.

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1 - University of Neuchâtel, Biology, Emil Argand 11, Neuchâtel, 2009, Switzerland
2 - University of Neuchâtel, Plant Physiology
3 - Monash University, School of Biological Sciences


Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P26070
Abstract ID:2573

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