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Title: THE ARABIDOPSIS RHD3 GENE IS REQUIRED FOR CELL WALL BIOSYNTHESIS AND ACTIN ORGANIZATION

Author
item HU, YUN - UNIV OF GEORGIA
item ZHONG, RUIQIN - UNIV OF GEORGIA
item MORRISON III, WILEY
item YE, ZHENG-HUA - UNIV OF GEORGIA

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2003
Publication Date: 7/3/2003
Citation: HU, Y., ZHONG, R., MORRISON III, W.H., YE, Z. THE ARABIDOPSIS RHD3 GENE IS REQUIRED FOR CELL WALL BIOSYNTHESIS AND ACTIN ORGANIZATION. PLANTA. 2003. VOL. 217(6). P. 912-921.

Interpretive Summary: Plants cells are enclosed in a rigid cell wall that gives strength to the plant as it grows so that it will not break under its own weight. Special cell types encircle the fibers as the plant increases in length holding them together and providing strength. Understanding how the cell deposition is oriented along the growing plant provides an important insight into the process of cell specialization. A mutant gene was identified and incorporated in a new plant to demonstrate its affect on the developing plant and allowed for the examination of the difference in fiber orientation as the plant matured. This work could play an important role in the basic understanding cell wall development and why some plants "lodge" or fall over in mild wind conditions thus reducing yields.

Technical Abstract: The Arabidopsis thaliana (L.) Heynh. ROOT HAIR DEFECTIVE3 (RHD3) gene has previously been shown to be essential for normal cell expansion [H. Wang et al. (1997) Genes Dev 11:799-811]. In this report, we demonstrated that mutation of the RHD3 gene in the Arabidopsis fragile fiber 4 (fra4) mutant caused a dramatic reduction in the wall thickness of fibers, vessels, and pith cells in the inforescence stems and, concomitantly, a decrease in the mechanical strength of stems. The reduced wall thickness in the fra4 mutant was accompanied by an alteration in cell wall composition. Consistent with the defective fiber and vessel wall phenotypes, the RHD3 gene exhibited a strong expression in developing fiber and xylem cells. We showed that the Arabidopsis genome contains two additional RHD3-like genes, one of which was expressed specifically in flowers. In addition, we found that mutation of the RHD3 gene caused an alteration in the organization of the actin cytoskeleton but no effects on cortical microtubules. Our findings suggest an essential role of RHD3 in cell wall biosynthesis and actin organization, both of which are known to be important for cell expansion.