Functional Characterization Of FC1 In Regulation Of Tolerance Of Arabidopsis Thaliana To Cadmium

Pollution of soil by the heavy metal cadmium(Cd)is a global environmental problem.The glutathione(GSH)-dependent phytochelatin(PC)synthesis pathway is one of the most important mechanisms contributing to Cd accumulation and tolerance.However,the regulation of this pathway is poorly understood.Here,we identified an Arabidopsis thaliana mutant fcl and cloned FC1 gene,which encodes ferrochelatase I(Ferrolyase,EC4.99.1.1)located in plastids.FC1 gene was involved in heme biosynthesis in non-photosynthetic tissues and induced by oxidative stress in photosynthetic tissues to supply heme for defensive hemoproteins,such as O3,drought,H2O2,wounding and cold.But,under Cd stress,it had not been functionally identified.In this paper,we genetically characterized the function of Arabidopsis FC1 and the pathway regulating the Cd stress.Overexpression of FC1 led to enhanced Cd accumulation and tolerance,whereas loss-of-function of FC1 resulted in decreased Cd accumulation and tolerance.FC1 over-expression conferred plant tolerance to Cd stress by enhancing primary root growth,fresh weigh and chlorophyll content,reducing accumulation of TBARS and H2O2 in shoot and root,O·2-in leaves and endogenous ROS in roots.Moreover,Helin treatment not only rescued the Cd-sensitive phenotype of the fcl mutant,but also improved the Cd tolerance of wild-type plants.FC1 over-expression led to enhanced tolerance was associated with GSH-dependent.In the presence of Hemin,enhanced Cd tolerance in WT and fcl was also associated with GSH-dependent.NPT,GSH and PC content were further increased with the presence of Hemin in Cd stress.Significantly,this Hemin-mediated Cd accumulation and tolerance is dependent on GSH-dependent PC concentrations via coordinated control of expression of genes involved in PC synthesis.Our results suggest that FC1 regulates the GSH-dependent PC synthesis pathway that contributes to Cd accumulation and tolerance in A.thaliana by coordinated control of gene expression.