Cho, Sung Ki , Chevalier, David , Lease, Kevin , Jinn, Tsung-Luo , Walker, John .
HAESA and HAESA-like 2 activate floral organ abscission in an ethylene-independent manner.
Organ abscission involves the regulated separation of cell layers to cause detachment of an organ from a plant. Our goal is to understand the molecular basis of this process. HAE and HSL2 exhibit similar promoter::GUS expression at floral abscission zones. Single knockout mutant lines of either gene do not show any phenotype, but the hae hsl2 double knockout mutant show an abscission-defect phenotype. The abscission defect observed in the double mutant could either be due to the inability to differentiate the abscission zone, or an inability to activate the cell separation process. Longitudinal sections through the abscission zone were examined by light microscopy and the fracture planes at the abscission zone when petals were forcibly removed were examined by scanning electron microscopy. These observations showed that the abscission zone in the hae hsl2 double mutant appears structurally normal. Furthermore, the hae hsl2 petal breakstrength at all flower positions was similar to that of wild type flowers that have not yet begun to abscise their petals. Taken together, these data support the idea that the role of HAE and HSL2 is to activate cell separation, rather than promote the differentiation of the abscission zone. Ethylene is also known to promote abscission; therefore we tested the ethylene-induced triple response and the effect of exogenous treatment on floral organ in the double mutant, revealing that HAE and HSL2 act independently of ethylene. We hypothesize that HAE and HSL2 activate abscission in an ethylene-independent manner by inducing the expression of enzymes that promote cell separation.
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1 - University of Missouri, Division of Biological Sciences, 304 Life Science Center, University of Missouri, Columbia, MO, 65211, USA
2 - University of Missouri, Division of Biological Sciences
3 - National Taiwan University, Dept of Life Science and Inst of Plant Biology
Arabidopsis floral organ abscission.
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM