Poster: Vegetative Development

Abs # 452: Different Effects of Auxin and Cytokinin on Tracheary Element Differentiation

Presenter:	Zhang, Xianchao , zhangxi@email.chop.edu
Authors	Zhang, Xianchao  (A)   Cote, Gary G. (B)   Hightower, Lawrence E. (A)   Crain, Richard C. (A)
Affiliations:	(A): Department of Molecular and Cell Biology, University of Connecticut (B): Biology Department, Radford University

Tracheary elements (TEs) can be induced to form in vitro from cultured single mesophyll cells of Zinnia elegans cv. Envy in the presence of the phytohormones auxin and cytokinin. This induced differentiation is a model system for developmentally programmed cell death in higher plants. The requirement for both auxin and cytokinin to effectively induce TE formation makes it difficult to elucidate the different roles of auxin and cytokinin in the process. We present data indicating that exogenous cytokinin is necessary and sufficient to stimulate complete TE formation and that exogenously added auxin potentiates the effect. TE formation induced by cytokinin alone is delayed two days compared to formation in cultures containing both hormones. Auxin alone causes dramatic cell expansion, and cell death, resulting in hollow dead cells lacking the secondary cell walls of normal TEs. We have shown that inositol phosphate production may be a signaling step in the induction of TEs (Zhang, et al., 2002, Planta 215:312-318), and we now report that cytokinin alone, but not auxin alone, triggers inositol trisphosphate production.