Interactions of Bacillus mojavensis and Fusarium verticillioides with a Benzoxazolinone (BOA) and its Transformation Product, APO

Abstract

The benzoxazolinones, specifically benzoxazolin-2(3H)-one (BOA), are important transformation products of the benzoxazinones that can serve as allelochemicals providing resistance to maize from pathogenic bacteria, fungi, and insects. However, maize pathogens such as Fusarium verticillioides are capable of detoxifying the benzoxazolinones to 2-aminophenol (AP), which is converted to the less toxic N-(2-hydroxyphenyl) malonamic acid (HPMA) and 2-acetamidophenol (HPAA). As biocontrol strategies that utilize a species of endophytic bacterium, Bacillus mojavensis, are considered efficacious as a control of this Fusarium species, the in vitro transformation and effects of BOA on growth of this bacterium was examined relative to its interaction with strains of F. verticillioides. The results showed that a red pigment was produced and accumulated only on BOA-amended media when wild type and the progeny of genetic crosses of F. verticillioides are cultured in the presence of the bacterium. The pigment was identified as 2-amino-3H-phenoxazin-3-one (APO), which is a stable product. The results indicate that the bacterium interacts with the fungus preventing the usual transformation of AP to the nontoxic HPMA, resulting in the accumulation of higher amounts of APO than when the fungus is cultured alone. APO is highly toxic to F. verticillioides and other organisms. Thus, an enhanced biocontrol is suggested by this in vitro study.

Metabolic Pathway Involved in 6-Chloro-2-Benzoxazolinone Degradation by Pigmentiphaga sp. Strain DL-8 and Identification of the Novel Metal-Dependent Hydrolase CbaA

“…When the modification is prevented due to a genetic mutation (FDB2), nontoxic 2-acetamidophenol (HPAA) may accumulate as a result of acetylation (49). During the BOA detoxification process, 2AP can also be spontaneously oxidized to produce 2-amino-3H-phenoxazin-3-one (APO), which is highly toxic to F. verticillioides (50) and exhibits greater allelopathic phytotoxicity toward barnyard grass (Echinochloa crus-galli) than BOA (51,52). Doratomyces stemonitis can utilize APO as a sole carbon source, but the utilization of this product seems to have a high energy demand (53).…”

Degradation of the benzoxazolinone class of phytoalexins by Fusarium pseudograminearum, a pathogenic fungus of wheat

“…Co-incubation of the endophytic bacterium Bacillius mojavensis, as a bio-control agent, with F. verticillioides appears to increase the production of toxic phenoxazinone whilst preventing the production of non-toxic malonamic acids by the Fusarium sp., thus giving preference to bacterium growth (Bacon et al, 2007). B. mojavensis was observed having a 100-fold higher phenoxazinone concentration tolerance compared to F. verticillioides.…”

“…However, 2-APO appears not to inhibit bacteria to the same degree (Atwal et al, 1992). As beneficial soil biota can act as antagonists against pathogenic fungi, are being explored for crop protection (Bacon et al, 2007), the identification of biota candidates that can perform gamma-lactamase (Fdb1-like) functions of benzoxazolinone degradation, producing 2-APO, that are also insensitive to 2-APO, may be beneficial for crop rhizosphere defences. Therefore, identification of fungal-antagonistic bacteria carrying FDB1 orthologs may be utilised as bio-control agents to reduce disease incidence.…”

“…Two antagonistic relationships have already been investigated for Fusarium species antagonism: Bacillus mojavensis inhibits the growth of the maize pathogen F. verticillioides via interference with benzoxazolinone detoxification via Fdb2 inhibition (Bacon et al, 2007);…”

Benzoxazolinone Detoxification and Degradation – A Molecule ́s Journey

“…The first step in the degradation of benzoxazolinone-2(3H)-one (BOA) is a hydrolysis yielding 2-aminophenol. This step is performed by bacteria as well, also by seed born ones (Bacon et al 2007;Burdziak et al, 2001). 2-Aminophenol is not stable but is spontaneously dimerized to 2-amino-3H-phenoxazin-3-one (APO) or it can be captured by several fungi which convert the compound to N-(2-hydroxyphenyl)malonamic acid (oHPMA) and 2-acetamidophenol (AAP) (Carter et al, 1999;Friebe et al, 1998;Glenn et al, 2001Glenn et al, , 2002Glenn et al, , 2003.…”