Poster: Hormone synthesis & metabolism

Abs # 484: Possible role of GhGLP1 in auxin signaling

Presenter:	Abdel-Mageed, H.A , s_hajar2001@yahoo.com
Authors	Abdel-Mageed, H.A  (A)   Fokar, M  (A)   Paxton, Payton  (B)   Allen, Randy D (A)
Affiliations:	(A): Departments of Biological Sciences & Plant Sciences, Texas Tech University (B): USDA-ARS Cropping Systems Research Laboratory

Cotton fibers are single specialized, highly elongated cells that grow from the seed integument. Although auxin is a critical phytohormone regulating fiber development, little is known about the mechanism by which auxin mediates fiber cell initiation and elongation. Using information from other plant species and in-silico transcriptomics to search for putative auxin binding protein, we identified a germin like protein (GLP) with an auxin binding protein motif, previously called GhGLP1. This protein is highly expressed during fiber development and does not appear to posses any enzymatic activities related to known germin like proteins. Transgenic Arabidopsis plants that constitutively over-express GhGLP1 under the control of the CaMV 35S promoter were constructed and their phenotype analyzed. These transgenic lines displayed changes suggestive of auxin hypersensitivity. Primary root growth of transgenic plants was reduced by 27 to 64% compared to the control plants. To assess auxin sensitivity in transgenic lines, we conducted a root elongation assay in the presence of auxin (IAA) and auxin transport inhibitor (NPA). Transgenic plants grown in various concentration of IAA were more sensitive to auxin than wild type plants, but show reduced sensitivity to NPA. These observations suggest that GhGLP1 may alter auxin signaling in Arabidopsis and raise the possibility that it could be involved in auxin signaling in cotton fiber development. Characterization of changes in gene expression due to GhGLP over-expression using microarray will be presented.