Poster: Integrative plant physiology

Abs # 38: Role of auxin in flower petal abscission in Arabidopsis thaliana

Presenter:	Warren, Lance A, warrla1@wfu.edu
Authors	Muday, Gloria K. (A)   Warren, Lance A (A)
Affiliations:	(A): Wake Forest University

Abscission of flower petals is a developmentally programmed stage in the life cycle of Arabidopsis thaliana. The balance of the hormones ethylene and auxin within the petal abscission zone (AZ) has been suggested to regulate the timing of flower abscission relative to other developmental events. The role of ethylene in promoting flower abscission has been shown, but although auxin has been suggested to also mediate petal abscission, this possibility has not been adequately tested. The position of each flower along the inflorescence correlates with the age of that flower. Thus, analysis of position of floral abscission along the inflorescence allows one to assay for delayed or accelerated abscission. To study the effect of auxin on timing of abscission, Arabidopsis inflorescences were treated with the auxin transport inhibitor, NPA (N-1-naphthylphthalamic acid) and the auxin, IAA (Indole-3-acetic acid). NPA regulates basipetal auxin transport in the inflorescence and may alter auxin movement into or out of the abscission zone. Furthermore, plants with auxin transport and sensitivity mutations were studied to clarify the effect of auxin on abscission. Methods for quantifying abscission involved analysis of visual phenotype comparisons, electron microscopy of floral AZs, flower petal break-strength assays, and GUS expression linked to promoters of two enzymes induced during abscission. NPA treatment of Arabidopsis inflorescences delays abscission. These results suggest that auxin and auxin transport, like ethylene, delay petal abscission. Similar treatments on ethylene insensitive plants, as well as auxin transport assays, should provide insight into whether auxin acts to alter ethylene synthesis or response or acts through an alternative pathway.