Poster: Late and Moved Abstracts

Abs # 1023: The ectopic expression of an Arabidopsis RING-H2 gene, AtRGZF, induces pleiotropic effects on plant growth and hormone signaling

Presenter:	Ko, Jae-Heung , ko@msu.edu
Authors	Ko, Jae-Heung  (A)   Kim, Jeong Hoe  (B)   Han, Kyung-Hwan  (A)
Affiliations:	(A): Department of Forestry, Michigan State University (B): MSU-DOE Plant Research Lab, Michigan State University

RING zinc-finger proteins play important roles in the regulation of development in a variety of organisms. AtRGZF encodes a small protein with a RING-H2 zinc-finger motif located at the C-terminus and an N-terminal transmembrane domain. Although antisense suppression of the gene in Arabidopsis plants did not show any visible phenotypic changes, its over expression in transgenic plants caused dramatic alterations in plant growth and development, which include shorter stature (i.e., shorter hypocotyls, petioles and stem), round-shaped leaves, impaired silique development and hyper-sensitivity to salt/osmotic stress. Moreover, the over-expression transgenic plants revealed pleiotropic phenotypes upon treatment of various plant hormones such as auxin, ABA, GA, and SA. To understand the functional role of AtRGZF gene, we compared the gene expression profiles between wild-type and the overexpression plants using Affymetrix ATH1 GeneChip (23K). Only 118 (0.5%) of the 22,591 genes on the genechip had significant changes in their expression in the overexpression plants, indicating that only specific gene sets of the genome were affected by the ectopic expression of the gene. Yeast two-hybrid assays showed that AtRGZF interacts with AtUBC8 (ubiquitin conjugating enzyme E2) and AtTLP9, which is implicated in the ABA signaling pathway. These data imply that the AtRGZF may be involved in the regulation of various hormone-signaling pathways through ubiquitin and/or proteasome-mediated substrate-specific degradation of proteins.