ASGSB 1998 Annual Meeting Abstracts

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REGULATION OF TCH4 GENE EXPRESSION IN ARABIDOPSIS THALIANA.   E.A. Iliev, W. Xu, and J.A. Braam. Dept of Biochemistry & Cell Biology, Rice University, Houston, Texas.

Arabidopsis TCH4 encodes a xyloglucan endotransglycosylase. Xyloglucan polymers are thought to crosslink cellulose microfibrils in the plant cell wall. TCH4 cleaves xyloglucans internally and ligates the newly generated ends onto new xyloglucan chains; our hypothesis is that this activity is used for cell growth and/or cell wall strengthening. TCH4::GUS fusions are expressed in rapidly growing tissues as well as sites predicted to be experiencing mechanical strain such as root-shoot junctions and vascular tissue. TCH4 expression is rapidly up-regulated in response to touch, darkness, and temperature extremes, as well as auxin and brassinosteroids. Using transgenic plants harboring TCH4 upstream sequences fused to reporter genes, we are identifying potential cis-regulatory elements conferring gene expression regulation. The region between –258 and –45 of TCH4 is sufficient to confer response to all the tested stimuli. Preliminary dissection of this region indicates that despite the complexity of TCH4 regulation, expression may be controlled by a single short 54 bp region. (Supported by NASA Specialized Center for Research and Training grant no. NAGW 5007).

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