56:	Expression patterns for selective expansin genes in Arabidopsis.

Authors:	Durachko, Daniel, M.(A)Cosgrove, Daniel, J.(A)
Affiliations:	(A): Penn State University
Presenter:	Cosgrove, Daniel J., fsl@psu.edu

Expansins are wall proteins with the unique ability to catalyze cell wall relaxation and wall extension (creep) in a pH-dependent manner in vitro. In Arabidopsis we have found that expansins comprise a large multi-gene family (see the web site at http://www.bio.psu.edu/expansins/). To evaluate the specific roles of individual expansin genes, we have begun to characterize expression patterns for individual genes, using promoter-GUS constructs and RT-PCR. To date we have found distinct patterns of expression for each of the expansin genes examined. For example, the AtExp4 promoter directs expression specifically to the vascular bundles throughout the plant. The AtExp1 promoter controls expression in the stomatal guard cells and very young vascular bundles. The AtExp11 promoter directs a diffuse expression in the leaf, but not in the epidermis or in the vascular bundles. The specificity of expression indicates that different cell types that make up the plant body express a different complement of expansin genes. Cell-specific control of gene expression of the different expansin family members thus seems to be a part of the cell-specific control of growth and differentiation.