Identification and characterization of copper-responsive proteins in arabidopsis

Abstract

For the successful development of a hyperaccumulating plant sufficient for use in phytoremediation strategies, a thorough understanding of the mechanism of hyperaccumulation is required. A proteomic survey of the response of plants to metal exposure is a step towards this understanding. The frd3-3 metal accumulating mutant of Arabidopsis thaliana and its non-accumulating wildtype parental ecotype, Columbia, were grown hydroponically in growth chamber experiments and exposed to copper in the growth medium. The responses of the global and copper-targeted proteomes were examined both spatially and temporally. Exposure to copper caused a general increase in protein abundance, however, a prolonged exposure to copper that approached toxicity caused a decrease in protein abundance. The protein species differed between the roots of the two genotypes, with more defense- and stress-related proteins, and fewer transport and storage proteins identified in the mutant when compared to the wildtype. Proteomic evidence suggests that in the mutant the uptake and transport of copper ions to the aerial tissues is regulated. The protein expression patterns over time demonstrate a constitutive expression of defense- and stress-related proteins in the mutant, whereas the wildtype expression was one of induction. The constitutive expression of key defense proteins suggests a “state-of-readiness” for metal exposure in the mutant. The plant response to reactive oxygen species, as a consequence of copper exposure, is important in the overall metal accumulation mechanism. A suppression of the oxidative burst produced upon exposure to heavy metals is suggested by the proteomic evidence.