Involvement of S-adenosylmethionine-dependent halide/thiol methyltransferase (HTMT) in methyl halide emissions from agricultural plants: isolation and characterization of an HTMT-coding gene from Raphanus sativus (daikon radish)

Abstract

Background: Biogenic emissions of methyl halides (CH 3 Cl, CH 3 Br and CH 3 I) are the major source of these compounds in the atmosphere; however, there are few reports about the halide profiles and strengths of these emissions. Halide ion methyltransferase (HMT) and halide/thiol methyltransferase (HTMT) enzymes concerning these emissions have been purified and characterized from several organisms including marine algae, fungi, and higher plants; however, the correlation between emission profiles of methyl halides and the enzymatic properties of HMT/ HTMT, and their role in vivo remains unclear.

Rice OsHOL1 and OsHOL2 proteins have S-adenosyl-L-methionine-dependent methyltransferase activities toward iodide ions

“…OsHOL1 and OsHOL2 belong to Cluster IV, together with other HOL proteins of monocotyledonous plants. OsHOL2 was more similar to HOL proteins of the other monocots than OsHOL1.e Rice Expression Pro le Database (RiceXPro; http:// ricexpro.dna.a rc.go.jp) (Sato et al 2010) showed that OsHOL1 is expressed mainly in the leaf blade, whereas OsHOL2 is expressed in the whole plant at lower levels than OsHOL1 (data not shown), implying their di erent physiological roles.Whereas methyltransferase activity toward iodide ions had been reported in crude extract prepared from rice tissues (Itoh et al 2009), it was not examined whether OsHOL1 and OsHOL2 possess SAMdependent methyltransferase activities toward iodide ions. Therefore, we first examined whether OsHOL1 and OsHOL2 have the activity toward iodide ions as well as bromide, chloride, and thiocyanate ions.…”

A Study on the Production and Emission of Marine-Derived Volatile Halocarbons

“…Homologues of this enzyme have been found in several organisms, such as higher plants (Attieh et al 2000;Itoh et al 2009), algae (Itoh et al 1997), fungi, and soil bacteria (Amachi et al 2001) In this study, various marine phytoplankton were cultivated in order to clarify the molecular formation mechanism of methyl halides and to establish a correlation between intracellular halide ion methyl transferase/halide ion thiol methyl transferase (HTM/HTMT) activity and CH 3 X emission. The enzyme genes were isolated from marine phytoplankton, verified, expressed in E. coli, and characterized in detail.…”

“…Experimental details for strains, cultivation of phytoplankton, analytical conditions of GC-MS, enzyme assay, preparation of genomic DNA, plasmid construc- tion, and expression and purification of recombinant enzymes are described in Itoh et al (2009) and Toda and Itoh (2010).…”

“…In future studies, the relationships between iodocarbon production and the characteristics of microorganisms, such as species composition, size, and bacterial activity, should be taken into consideration in order to evaluate the importance of biogenic iodocarbon emissions from the open ocean. To examine the relationships between HTMT activity and the emission strength of methyl halides, several marine phytoplankton that are reported to have HTMT activity (Itoh et al 2009), marine diatoms and marine picoplankton, including Ostreococcus sp. and Synecoccus sp.…”

“…(Agmenellum) CCAP1400/1, and the HTMT gene of P. tricornutum was expressed in E. coli and characterized in detail to clarify the HTMT reaction at the molecular level. The P. tricornutum HTMT (PtHTMT) gene was isolated by in silico screening on the P. tricornutum genome database on the basis of the HTMT gene (RsHTMT) of Raphanus sativus (daikon radish) (Itoh et al 2009). We detected one homologous gene in the P. tricornutum genome database (Scala et al 2002) indicating an homology of about 30% with RsHTMT.…”