Poster: Hormones

Abs # 634: Reduction of cytokinin biosynthesis genes in Arabidopsis

Presenter:	Tomscha, Jennifer L, tomscha@email.unc.edu
Authors	Tomscha, Jennifer L (A)   Sullivan, Katie L (A)   Kieber, Joe J (A)
Affiliations:	(A): UNC-Chapel Hill

Although the hormone cytokinin has long been studied for its ability to stimulate plant cell division in culture, fundamental processes that absolutely require cytokinin for normal growth and development have not yet been identified. Previous work in the field has succeeded in up-regulating levels of the hormone in-vivo by either exogenous cytokinin application or transgenic expression of bacterial isopentenyl transferase genes. Overexpression of cytokinin oxidase, which degrades a subset of cytokinin compounds, has also been achieved in heterologous systems and shown to reduce cytokinin levels (Werner et al., 2001 PNAS 98:10487-10492), as has heterologous expression of a gene that inactivates and stores cytokinins, zeatin O-glucosyltransferase (Martin et al., 2001 In Vitro Cell Dev Biol - Plant 37:354-360). Although cytokinins were reduced in these studies, they were not completely eliminated. The first plant cytokinin biosynthesis genes, the Arabidopsis isopentenyl transferase genes (AtIPTs), have recently been identified (Takei et al., 2001 JBC 276:26405-26410; Kakimoto, 2001 Plant Cell Physiol 42:677-685), . We are currently working with the AtIPTs to develop plants that lack the ability to produce cytokinins. AtIPTs consist of a seven member family, and their expression patterns overlap throughout the plant with few exceptions. Detailed expression analysis of the AtIPT gene family will be presented, as well as the characterization of T-DNA insertion lines and RNAi lines.