Poster: Phytoremediation

Abs # 988: RNA interference of Arabidopsis metallothionein transcripts produce cadmium sensitive phenotypes

Presenter:	Zimeri, Anne Marie S, zimeri@arches.uga.edu
Authors	Zimeri, Anne Marie S (A)   Meagher, Richard B (A)
Affiliations:	(A): University of Georgia

The Arabidopsis thaliana genome contains eleven metallothionein (MT)-like sequences with classical cysteine rich domains separated by spacer sequences. Phylogenic analysis of these and other plant MTs revealed four ancient classes of sequences that predate the monocot-dicot divergence 200 million years ago. It is likely that these ancient classes of MTs have been preserved in plant genomes because their distinct metal binding properties provide protection from toxic metals and elevated levels of nutrient metals. Each class has a distinct in vivo metal binding affinity that stabilizes newly translated MTs. Based on protein stability assays, MT1 binds cadmium with greatest affinity over other thiol-reactive metal ions. We hypothesized that suppression of these four MT1 class members would render Arabidopsis plants hypersensitive to cadmium. RNA interference (RNAi) was used to disrupt translation of an entire MT1 class. A portion of the coding sequence that is well conserved among all four members of MT1 class, but not in classes 2, 3, or 4 was expressed from a vegetative constitutive actin promoter. Protein levels were reduced in RNAi lines based on western blots probed with MT1 class specific monoclonal antibodies prepared for this study. Plant growth on medium containing 50 mM cadmium severely inhibited the MT1-RNAi lines as compared to wild-type. In addition, these lines accumulated less cadmium per gram of tissue than wild-type. Future experiments will include the overexpression of MT1 in an attempt to engineer plants that hyperaccumulate cadmium for potential use in phytoremediation strategies.