Poster: Hormones

Abs # 629: Expression, purification and characterization of auxin binding protein from Sinapis arvensis L. using various expression systems

Presenter:	Haggerty, Kristine M, khaggert@uoguelph.ca
Authors	Haggerty, Kristine M (A) (C)  Zheng, H G (A) (C)  Krell, P J (B) (C)  Hall, J C (A) (C)
Affiliations:	(A): Department of Environmental Biology (B): Department of Microbiology (C): University of Guelph

An auxinic herbicide resistant (R) biotype of Sinapis arvensis L. (wild mustard) has been identified in a Manitoba field. The precise mechanism of resistance is unknown, but previous studies suggest a relationship between the binding activity of auxin binding protein (ABP), the putative target site, and sensitivity to these herbicides. Characteristics of the R and S wild mustard biotype ABP preparations were previously examined. Both ABP preparations have similar substrate ([³H] indole-3-acetic acid) and time course profiles, but Scatchard analysis revealed differences between the two biotypes; the R biotype lacks a high-affinity population of ABP which is present in the S biotype. Also, differences were found in the nucleotide-derived amino acid sequences of ABP1 present in both biotypes. The focus of this work was to express ABP1 protein from the S-biotype of wild mustard using various expression systems to uncover more about its function in auxin and auxinic herbicide binding. The ABP1 protein was expressed using a baculovirus expression system (eukaryotic) and a GST-fusion protein expression system (prokaryotic) and several binding assays were performed. Various auxin affinity columns, ammonium sulphate precipitation assays, and size exclusion chromatography assays failed to show auxin binding by the recombinant ABP1. Presently, the ABP1 from Zea mays is being expressed in the GST-fusion protein system to determine its capability of binding various auxins. This work may determine if there are differences between the auxin binding affinities of ABP1 from monocotyledonous and dicotyledonous plants and may illustrate the potential role of ABP in auxinic herbicide resistance.