Arabidopsis HARMLESS TO OZONE LAYER Protein Methylates a Glucosinolate Breakdown Product and Functions in Resistance to Pseudomonas syringae pv. maculicola

Abstract

Almost all of the chlorine-containing gas emitted from natural sources is methyl chloride (CH 3 Cl), which contributes to the destruction of the stratospheric ozone layer. Methyl chloride (CH 3 Cl) is the most abundant halohydrocarbon emitted into the atmosphere and constitutes about 17% of the chlorine currently in the stratosphere (1). CH 3 Cl is derived mainly from natural sources and contributes to the destruction of the stratospheric ozone layer. As the total abundance of ozone-depleting gases such as chlorofluorocarbons in the atmosphere has begun to decrease in recent years as a result of The Montreal Protocol on Substances That Deplete the Ozone Layer, the impact of CH 3 Cl emission from natural sources will become greater on the atmospheric chemistry. CH 3 Cl emission into the atmosphere has been estimated at 1,700 -13,600 Gg/year (1), which underscores the great uncertainty of the estimation. Oceans (2), biomass burning (3), woodrotting fungi, and coastal salt marshes (4) are the major sources of CH 3 Cl production. Recently, it was reported that large amounts of CH 3 Cl are emitted from tropical and subtropical plants, which are hence considered as the major sources of CH 3 Cl (5-7). It was estimated that the CH 3 Cl emission from tropical plants could account for 30 -50% of the global CH 3 Cl emission (8). To accomplish an accurate estimation of CH 3 Cl production in the atmosphere through "bottom-up" approaches, elucidating the mechanisms and physiological functions of CH 3 Cl emission from plants will be important.The biological synthesis of methyl halides has been demonstrated mainly by biochemical analyses. The enzymatic activities that transfer a methyl group from S-adenosyl-L-methionine (SAM) 2 to halide ions (Cl Ϫ , Br Ϫ , I Ϫ ), which synthesize methyl halides, were first discovered in cell-free extracts of Phellinus pomaceus (a white rot fungus), Endocladia muricata (a marine red alga), and Mesembryanthemum crystallinum (ice plant, a halophytic plant) (9). Enzyme purification and cDNA cloning of the methyl chloride transferase (MCT) was first reported with Batis maritima, a halophytic plant that grows abundantly in salt marshes. As high concentrations of ions such as Cl Ϫ are often detrimental to plants, halophytic plants are considered to possess various salt tolerance mechanisms. MCT was hypothesized to control and regulate the internal concentration of Cl Ϫ , rich in the habitat in which halophytic plant grows (10, 11).In the meantime, purification of thiol methyltransferase (TMT), which methylates bisulfide (HS 2 The abbreviations used are: SAM, S-adenosyl-L-methionine; GC-ECD, gas chromatography equipped with an electron capture detector; GC-MS, gas chromatography/mass spectrometry; HOL, harmless to ozone layer; HPLC, high performance liquid chromatography; MCT, methyl chloride transferase; MS, Murashige-Skoog; RT, reverse transcription; SAH, S-adenosyl-Lhomocysteine; TMT, thiol methyltransferase.

The type III effector AvrXccB in Xanthomonas campestris pv. campestris targets putative methyltransferases and suppresses innate immunity in Arabidopsis

“…hol1 seedlings are more susceptible to infection by P. syringae pv. maculicola (Nagatoshi and Nakamura, ). Isoflavone‐ O ‐methyltransferase (IOMT) is also a SAM‐MT transferring a methyl group from SAM to isoflavones, yielding the methyl ether derivatives.…”

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

“…All kinetic analyses of plant HOL family proteins reported to date have been performed using proteins from Brassicales plants. A physiological substrate of AtHOL1 protein was suggested to be a thiocyanate ion produced by the catabolism of indole glucosinolates, which are characteristic secondary metabolites among Brassicales plants (Midorikawa et al 2009;Nagatoshi and Nakamura 2009). ese results suggested that Brassicales plants have HOL proteins that play a physiological role speci c to Brassicales plants.…”

The metabolomics of oxidative stress

“…In Brassica species, glucosinolates are an important class of stress-related compounds. A mutant deficient in Harmless to Ozone Layer1 (HOL1), so called because it has only low emissions of ozone-damaging methyl halides, shows decreased resistance to bacteria, associated with compromised ability to methylate glucosinolate breakdown products (Nagatoshi and Nakamura, 2009). Together with the glucosinolate-cleaving enzyme (myrosinase) and SA-linked PR proteins (PR2, PR5), HOL1 showed increased phosphopeptide signals in cat2 and other mutants that show constitutive redox perturbation and increased resistance to pathogens (Trotta et al, 2011;Li et al, 2014).…”