Structure and Bioactivity of Thiosulfinates Resulting from Suppression of Lachrymatory Factor Synthase in Onion

Aoyagi, Morihiro; Kamoi, Takahiro; Kato, Masahiro; Sasako, Hiroshi; Tsuge, Nobuaki; Imai, Shinsuke

doi:10.1021/jf202446q

Cited by 23 publications

(57 citation statements)

References 25 publications

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Section: Discussionmentioning

confidence: 99%

“…The silencing of LFS has been used in laboratory settings to create “tearless” onions (5, 38). The lack of LFS activity in these lines drives increased flux of isoalliin into the dramatically increased production of 1-propenyl-based thiosulfinates after tissue damage (5, 38). Consistent with the capacity of garlic, which lacks an LFS-like enzyme, to produce nearly 100 fold more thiosulfinates than onion per g fresh weight, and the paucity of garlic bulb infecting bacterial pathogens in general, we hypothesize that these LFS-silenced onion lines should display increased resistance to P. ananatis infection by overwhelming the pathogen’s capacity for thiosulfinate tolerance.…”

Section: Discussionmentioning

confidence: 99%

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Pantoea ananatisdefeatsAlliumchemical defenses with a plasmid-borne virulence gene cluster

Stice

Khang

et al. 2020

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Onion (Allium. cepa L), garlic (A. sativum L.), and other members of the Allium genus produce volatile antimicrobial thiosulfinates upon cellular damage. Allicin has been known since the 1950s as the primary antimicrobial thiosulfinate compound and odorant produced by garlic. However, the roles of endogenous thiosulfinate production in host-bacterial pathogen interactions have not been described. The bacterial onion pathogen Pantoea ananatis, which lacks both the virulence Type III and Type II Secretion Systems, induces necrotic symptoms and extensive cell death in onion tissues dependent on a proposed secondary metabolite synthesis chromosomal gene cluster. We found strong correlation between the genetic requirements for P. ananatis to colonize necrotized onion tissue and its capacity for tolerance to the thiosulfinate allicin based on the presence of an eleven gene, plasmid-borne, virulence cluster of sulfur/redox genes. We have designated them ‘alt’ genes for allicin tolerance. We show that allicin and onion thiosulfinates restrict bacterial growth with similar kinetics. The alt gene cluster is sufficient to confer allicin tolerance and protects the glutathione pool during allicin treatment. Independent alt genes make partial phenotypic contributions indicating that they function as a collective cohort to manage thiol stress. Our work implicates endogenous onion thiosulfinates produced during cellular damage as mediators of interactions with bacteria. The P. ananatis-onion pathosystem can be modeled as a chemical arms race of pathogen attack, host chemical counter-attack, and pathogen resistance.Significance StatementAlliums (e.g. onion and garlic), after sustaining cellular damage, produce potent antimicrobial thiosulfinates that react with cellular thiols. The bacterial onion pathogen Pantoea ananatis, which lacks the virulence Type III and Type II Secretion Systems, induces cell death and necrotic symptoms on onions. We have identified a plasmid-borne cluster of sulfur/redox virulence genes that 1) are required for P. ananatis to colonize necrotized onion tissue, 2) are sufficient for tolerance to the thiosulfinates, and, 3) protect the glutathione pool during thiosulfinate treatment. We propose that the thiosulfinate production potential of Allium spp. governs Allium-bacterial interaction outcomes and that the P. ananatis-onion pathosystem can be modeled as a chemical arms race of attack and counterattack between the pathogen and host.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Pantoea ananatisdefeatsAlliumchemical defenses with a plasmid-borne virulence gene cluster

Stice

Khang

et al. 2020

Preprint

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“…14,15 In agreement with the proposed catalytic function of this enzyme, silencing LFS expression resulted in the generation of a “tearless” onion that did not exert eye irritation properties upon disruption of the onion tissue. 16,17 Importantly, changes in the relative concentration of LFS and alliinase have had a profound effect on the organosulfur metabolite profile in these genetically modified plants. 18 These results directly indicate that alliinase cleaves ( E )-S-(1-propenyl)cysteine S -oxide to provide sulfenic acid substrate for LFS to yield LF (Figure 1).…”

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confidence: 99%

Enzyme That Makes You Cry–Crystal Structure of Lachrymatory Factor Synthase from Allium cepa

et al. 2017

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The biochemical pathway that gives onions their savor is part of the chemical warfare against microbes and animals. This defense mechanism involves formation of a volatile lachrymatory factor (LF) ((Z)-propanethial S-oxide) that causes familiar eye irritation associated with onion chopping. LF is produced in a reaction catalyzed by lachrymatory factor synthase (LFS). The principles by which LFS facilitates conversion of a sulfenic acid substrate into LF have been difficult to experimentally examine owing to the inherent substrate reactivity and lability of LF. To shed light on the mechanism of LF production in the onion, we solved crystal structures of LFS in an apo-form and in complex with a substrate analogue, crotyl alcohol. The enzyme closely resembles the helix-grip fold characteristic for plant representatives of the START (star-related lipid transfer) domain-containing protein superfamily. By comparing the structures of LFS to that of the abscisic acid receptor, PYL10, a representative of the START protein superfamily, we elucidated structural adaptations underlying the catalytic activity of LFS. We also delineated the architecture of the active site, and based on the orientation of the ligand, we propose a mechanism of catalysis that involves sequential proton transfer accompanied by formation of a carbanion intermediate. These findings reconcile chemical and biochemical information regarding thioaldehyde S-oxide formation and close a long-lasting gap in understanding of the mechanism responsible for LF production in the onion.

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“…1). The population of mostly volatile end products [ e.g ., dialk(en)yl thiosulfinates ( 5 ), cepathiolanes ( 6 ), cepaenes ( 7 ), polysulfides ( 8 ), and zwieberanes ( 9 )] contributes to determining alliaceous smells and flavors (7, 8).…”

Section: Introductionmentioning

confidence: 99%

“…In organisms lacking LFS genes, for example, garlic ( Allium sativa ), free sulfenic acids are condensed immediately, and thus are just destined to produce dialk(en)yl thiosulfinates (2, 6). Gene silencing of onion LFS derives increases of ( 5 ) and ( 9 ) isomers, displaying a metabolite composition similar to that of garlic (8, 27).…”

Section: Introductionmentioning

confidence: 99%

Structure ofAlliumlachrymatory factor synthase elucidates catalysis on sulfenic acid substrate

Arakawa

Sato

Takabe

et al. 2017

Preprint

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18Natural lachrymatory effects are invoked by small volatile S-oxide 19 compounds. They are produced through alkene sulfenic acids by the action of 20 lachrymatory factor synthase (LFS). Here we present the crystal structures of 21 onion LFS (AcLFS) revealed in solute-free and two solute-stabilized forms. 22 Significance statement 38Crushing of onion liberates a volatile compound, syn-propanethial S-oxide 39 (PTSO), which causes lachrymatory effect on humans. We present the crystal 40 structures of onion LFS (AcLFS), the enzyme responsible for natural production 41 of PTSO. AcLFS features a barrel-like fold, and mutagenic and inhibitory 42 analyses revealed that the key residues are present in the central pocket, 43 harboring highly concentrated aromatic residues plus a dyad motif. The 44 architecture of AcLFS is widespread among proteins with various biological 45 functions, such as abscisic acid receptors and polyketide cyclases, and 46 comparisons with these homologs indicate that unique steric and electronic 47 properties maintain the pocket as a reaction compartment. We propose the 48 molecular mechanism behind PTSO generation and shed light on biological 49 decomposition of short-lived sulfur species. 50 51 Results 98Overall structure and confirmation of the active site 99

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Structure and Bioactivity of Thiosulfinates Resulting from Suppression of Lachrymatory Factor Synthase in Onion

Cited by 23 publications

References 25 publications

Pantoea ananatisdefeatsAlliumchemical defenses with a plasmid-borne virulence gene cluster

Pantoea ananatisdefeatsAlliumchemical defenses with a plasmid-borne virulence gene cluster

Enzyme That Makes You Cry–Crystal Structure of Lachrymatory Factor Synthase from Allium cepa

Structure ofAlliumlachrymatory factor synthase elucidates catalysis on sulfenic acid substrate

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