Observation of Transmethylation from Methionine into Choline in the Intact Mycelia of <i>Pyricularia oryzae</i> by ¹³C NMR under the Influence of Fungicides

Abstract

Transmethylation from methionine into choline in the intact mycelia of Pyricularia oryzae and the effects of fungicides on it were observed by 13C NMR. P. oryzae was incubated with [methyl-13C]methionine. After 3 hr incubation, signal at 54.9 ppm, corresponding to the chemical shift of -N-CH3, was observed in the 13C NMR spectrum of the mycelia and its intensity increased with incubation time up to 24 hr. From the resultant mycelial cells, choline and phosphatidylcholine were isolated, and labeled N-methyl group was found in them. The signal intensity of the N-methyl was most remarkable in the water soluble fraction, suggesting that the signal at 54.9 ppm in the spectra of the mycelia was attributable to N-methyl group of choline. The methyltransfer from [methyl-13C]methionine into choline could be observed by 13C NMR. When 100 ppm of IBP was added to the incubation mixture, this methyltransfer was inhibited during 3 to 6 hr. Addition of 40 ppm of isoprothiolane had a similar effect.

A Putative Zn2Cys6 Transcription Factor Is Associated With Isoprothiolane Resistance in Magnaporthe oryzae

“…There are similarities between organophosphorus thiolate (PTL) fungicides and IPT, particularly because cross-resistance between IPT and phosphorothiolates and negative cross-resistance between IPT and phosphoramidates have been observed (Katagiri, 1977 ). With 13 C labeling, transmethylation yielding choline was found to be inhibited by PTL fungicides and IPT (Yoshida et al, 1984 ). Thus, IPT was thought to be a choline biosynthesis inhibitor similar to PTL fungicides.…”

“…Thus, IPT was thought to be a choline biosynthesis inhibitor similar to PTL fungicides. There are two main pathways for choline biosynthesis, and the Kennedy's pathway is the principal route of phosphatidyl-choline biosynthesis in M. oryzae (Yoshida et al, 1984 ). Thus, we sequenced PEAMT, CHO2 , and OPI3 from resistant mutants and their parental wild type isolates (Hu et al, 2014 ).…”

“…IPT significantly inhibits penetration and growth of infective hyphae, mycelial growth is inhibited completely at 20 μg/ml IPT, with emergence of infection pegs is reduced by 96% at 10 μg/ml IPT on rice leaves (Araki and Miyagi, 1976 ). IPT is considered a choline biosynthesis inhibitor (CBI) similar to organophosphorus fungicides because the inhibition of transmethylation from methionine into choline was observed in intact mycelia when incubated with 100 μg/ml IBP (Iprobenfos, another CBI) or 40 μg/ml IPT (Yoshida et al, 1984 ; Uesugi, 2001 ). However, the mode of action of IPT against M. oryzae is not fully understood.…”

The velvet family proteins mediate low resistance to isoprothiolane inMagnaporthe oryzae

“…It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted November 22, 2022. ; https://doi.org/10.1101/2022.11.20.517298 doi: bioRxiv preprint only effective in controlling rice blast, but is also used as insecticide to control rice plant hopper [6], and as plant-growth regulator to promote the growth of plant roots [7]. IPT inhibits the methylation of phosphatidylethanolamine to phosphatidylcholine, and is thus considered as a choline biosynthesis inhibitor with cross resistance with organophosphorus fungicides such as iprobenfos [8,9]. Resistance to IPT (also known as Fuji One) in M. oryzae has already been detected in rice fields in recent years [10], but little is known about the molecular basis of resistance.…”

Fungal choline biosynthesis - a target for controlling rice blast

“…In Greenberg's pathway, the transmethylation occurs at the final step, while in Kennedy's pathway, it occurs at the preliminary step yielding choline, a precursor to be further incorporated into phosphatidylcholine. Using 13 C labeling studies, Yoshida showed that Kennedy's pathway is the principal route of phosphatidylcholine biosynthesis in the rice blast fungus (Yoshida, 1984), and that the transmethylation yielding choline is inhibited by phosphorothiolates and isoprothiolane (Figure 2). Phosphorothiolates and isoprothiolane were thus classified as choline biosynthesis inhibitors (CBIs).…”