In vivo and in vitro evidence for the inhibition of homogentisate solanesyltransferase by cyclopyrimorate

Abstract

BACKGROUND Cyclopyrimorate is a highly effective bleaching herbicide discovered by Mitsui Chemicals Agro, Inc. The target site was recently reported to be homogentisate solanesyltransferase (HST) in the plastoquinone (PQ) biosynthesis pathway on the basis of the number of intermediates in cyclopyrimorate‐treated plants and in vitro HST assays. Here, the target site of cyclopyrimorate was further explored using both in vivo and in vitro experiments. RESULTS The cyclopyrimorate‐dependent bleaching effect on Arabidopsis thaliana was reversed by decyl PQ, suggesting that this symptom is attributable to the inhibition of PQ biosynthesis. Furthermore, homogentisate (HGA), a substrate of HST, weakly reversed the bleaching effect of cyclopyrimorate in a dose‐dependent manner. We expected that the weak reversal by HGA was due to competitive inhibition by cyclopyrimorate or des‐morpholinocarbonyl cyclopyrimorate (DMC), a metabolite of cyclopyrimorate in plants that exhibit higher HST‐inhibitory activity as compared to cyclopyrimorate. Kinetic analysis was therefore conducted using DMC. DMC inhibited HST competitively with respect to HGA, and was a mixed non‐competitive inhibitor with respect to the other substrate, farnesyl diphosphate. Moreover, neither cyclopyrimorate nor DMC inhibited 2‐methyl‐6‐phytyl‐1,4‐benzoquinone/2‐methyl‐6‐solanesyl‐1,4‐benzoquinone methyltransferase, which is located downstream of HST in the PQ biosynthesis pathway. CONCLUSIONS The target site of cyclopyrimorate and DMC is HST, which is a novel target site for commercial herbicides. © 2019 Society of Chemical Industry

Identification of the new prenyltransferase Ubi-297 from marine bacteria and elucidation of its substrate specificity

“…The third cluster of Ptases (G3) (20–100% pairwise identity) displayed similarities to geranylgeranylglyceryl phosphate synthases (EC 2.5.1.42), which are involved in the formation of polar membrane lipids of archaea and other bacteria [ 20 ], while group G4 contained close homologs of the protoheme IX farnesyltransferase (EC 2.5.1.141) (23–100% pairwise identity) responsible for heme O production in bacteria like E. coli [ 21 – 22 ]. However, no representatives of the remaining four Ptase groups G6–G8, which encode for ubiquinone biosynthesis (G5), decaprenyl-phosphate phosphoribosyltransferases (EC 2.4.2.45, G6) as reported in Mycobacteriaceae [ 23 ], chlorophyll synthases (EC 2.5.1.62, G7) [ 24 ] or homogentisate Ptases (EC 2.5.1.117, G8) [ 25 ], were found within the investigated genomes of Flavobacteria and Saccharomonospora representatives.…”

The nexus between reactive oxygen species and the mechanism of action of herbicides

“…Cyclopyrimorate is a proherbicide, so its desmorpholinocarbonyl cyclopyrimorate metabolite is the active form inhibiting HST ( 79 ). As with other bleaching herbicides, the herbicidal activity of HST inhibitors does not rely primarily on ROS accumulation ( 80 ). Since HST is downstream from the reaction catalyzed by HPPD in the PQ biosynthesis, the herbicidal activity of cyclopyrimorate is enhanced in tank mix with group 27 herbicides.…”

N‐benzyl‐2‐methoxy‐5‐propargyloxybenzoamides, a new type of bleaching herbicides targeting the biosynthesis pathway of plastoquinone

“…10 Up to now, more than a dozen HPPD herbicides have been successfully commercialized and widely used in weed management. 11 Another progress reported in recent years is the commercialization of herbicide cyclopyrimorate, a homogentisate solanesyltransferase (HST, group 33) inhibitor developed by Mitsui Chemicals Agro, Inc. 12 HST is a downstream enzyme of HPPD in the PQ biosynthesis pathway, and it catalyzes the formation of 2-methyl-6-solanesyl-1,4-benzoquinol (MSBQ). 13 Aclonifen structurally belongs to diphenylether (DPE) herbicides, but its mode of action is different from other DPE herbicides which act on protoporphyrinogen oxidase (PPO, group 14).…”