Arabidopsis thaliana outer ovule integument morphogenesis: ectopic expression of KNAT1 reveals a compensation mechanism.
BACKGROUND
The Arabidopsis outer ovule integument is a simple two-cell layered structure that grows around the developing embryo and develops into the outer layer of the seed coat. As one of the functions of the seed coat is the protection of the plant embryo, the outer ovule integument is an example for a plant organ whose morphogenesis has to be precisely regulated.


RESULTS
To better characterise outer ovule integument morphogenesis, we have isolated some marker lines that show GFP expression in this organ. We have used those lines to identify distinct cell types in the outer integument and to demonstrate similarities between leaves and the outer integument. Using confocal microscopy, we showed that cell sizes and shapes differ between the two cell layers of the outer integument. Expression of KNAT1 in the integuments leads to extra cell divisions specifically in the outer layer of the outer integument. This is being compensated for by a decrease of cell volume in this layer, thus showing that mechanisms exist to control proper ovule integument morphogenesis.


CONCLUSIONS
The Arabidopsis outer ovule integument can be used as a good model system to study the basic principles of plant organ morphogenesis. This work provides new insights into its development and opens new possibilities for the identification of factors involved in the regulation of cell division and elongation during plant organ growth.
Truernit
Elisabeth
E
University of Cambridge, Department of Plant Sciences, Downing Site, Cambridge CB2 3EA, UK. etruernit@versailles.inra.fr
Haseloff
Jim
J
D017360:Arabidopsis / Q000196:embryology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D035264:Flowers / Q000196:embryology / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018613:Microscopy, Confocal; D008954:Models, Biological; D009024:Morphogenesis / Q000235:genetics*; D012639:Seeds / Q000196:embryology / Q000235:genetics
D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C092212:KNAT1 protein, Arabidopsis