title: Genetic control of methyl halide production in Arabidopsis.
abstract: Methyl chloride (CH(3)Cl) and methyl bromide (CH(3)Br) are the primary carriers of natural chlorine and bromine, respectively, to the stratosphere, where they catalyze the destruction of ozone, whereas methyl iodide (CH(3)I) influences aerosol formation and ozone loss in the boundary layer. CH(3)Br is also an agricultural pesticide whose use is regulated by international agreement. Despite the economic and environmental importance of these methyl halides, their natural sources and biological production mechanisms are poorly understood. Besides CH(3)Br fumigation, important sources include oceans, biomass burning, tropical plants, salt marshes, and certain crops and fungi. Here, we demonstrate that the model plant Arabidopsis thaliana produces and emits methyl halides and that the enzyme primarily responsible for the production is encoded by the HARMLESS TO OZONE LAYER (HOL) gene. The encoded protein belongs to a group of methyltransferases capable of catalyzing the S-adenosyl-L-methionine (SAM)-dependent methylation of chloride (Cl(-)), bromide (Br(-)), and iodide (I(-)) to produce methyl halides. In mutant plants with the HOL gene disrupted, methyl halide production is largely eliminated. A phylogenetic analysis with the HOL gene suggests that the ability to produce methyl halides is widespread among vascular plants. This approach provides a genetic basis for understanding and predicting patterns of methyl halide production by plants.
authors.affiliation: Department of Earth System Science, University of California, Irvine, Irvine, CA 92697-3100, USA. rrhew@atmos.berkeley.edu
authors.forename: Robert C
authors.initials: RC
authors.lastname: Rhew
authors.forename: Lars
authors.initials: L
authors.lastname: Østergaard
authors.forename: Eric S
authors.initials: ES
authors.lastname: Saltzman
authors.forename: Martin F
authors.initials: MF
authors.lastname: Yanofsky
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D002874:Chromosome Mapping; D006842:Hydrocarbons, Brominated / Q000378:metabolism*; D006847:Hydrocarbons, Iodinated / Q000378:metabolism*; D008737:Methyl Chloride / Q000378:metabolism*; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny
chemical_list: D006842:Hydrocarbons, Brominated; D006847:Hydrocarbons, Iodinated; C005218:methyl bromide; D008737:Methyl Chloride; C014055:methyl iodide; D008780:Methyltransferases; C459582:S-adenosyl-L-methionine halide ion methyltransferase