Zea Mays: Benzoxazolinone Detoxification Under Sulfur Deficiency Conditions—A Complex Allelopathic Alliance Including Endophytic Fusarium Verticillioides

Abstract

Benzoxazolinone detoxification is similar in plants grown under sulfur deficiency conditions and in control plants grown with an optimal S supply. However, when S-deficient plants were treated with metolachlor before benzoxazolin-2(3H)-one (BOA) incubation, detoxification was reduced, as indicated by a lower accumulation of the detoxification products BOA-6-O-glucoside and glucoside carbamate and by a loss of BOA-6-OH glucosyltransfease activity. Root colonizing microorganisms and the endophytic fungus Fusarium verticillioides participated in benzoxazolinone detoxification by converting the compound to 2-acetamidophenol (AAP) or O-hydroxyphenyl malonamic acid (OHPMA), a process accompanied by the appearance of phenoxazinone. Maize roots, however, absorbed AAP and OHPMA only in traces. Absorbed traces of OHPMA stimulated maize radicle growth, and traces of AAP stimulated cress. Phenoxazinone inhibited the growth of cress radicles at concentrations higher than 500 microM, whereas maize radicles were hardly affected. F. verticillioides did not convert benzoxazolinone to any known microbial degradation product when the medium of maize seedlings was inoculated with the fungus under sterile condition. Plant-fungus interactions seem to be important in plant survival of allelopathic attacks. This study points to a complicated network of allelopathic interactions that are influenced by biotic and abiotic factors, including herbicides.

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

“…However, interactive microbial activity was not considered relevant. As established here and by others (Gagliardo and Chilton 1992;Fomsgaard et al 2004;Fritz and Braun 2006), however, APO is an important microbial transformation product of AP, although the interactions are perhaps exceeding complexity as observed here and by others (Macias et al 2005;Knop et al 2007). Fig.…”

“…This concentration was considerably less than that used here and elsewhere (Macias et al 2005;Martyniuk et al 2006;Krogh et al 2006), which are concentrations reported to occur naturally (Martyniuk et al 2006). Perhaps the growth reduction observed in F. verticillioides by Knop et al (2007) is reflective of the small amount of APO used. However, statistical significance was not assigned to the 14% reduction observed.…”

“…The silica gel plates were prepared following the procedure of Glenn et al (2001) detoxify it within the 2-wk observation period. Knop et al (2007) reported that F. verticillioides could utilize APO as a C-source, but indicated that its growth was reduced by 14% when cultured with 1 μM of APO. This concentration was considerably less than that used here and elsewhere (Macias et al 2005;Martyniuk et al 2006;Krogh et al 2006), which are concentrations reported to occur naturally (Martyniuk et al 2006).…”

“…This is the first report to show that in the presence of a bacterium on BOA-amended medium there is an increased expression of in vitro toxicity to a fungus, which usually has the capability to detoxify BOA into decomposition products. Recently, Knop et al (2007) demonstrated that detoxification of BOA by F. verticillioides was greatly reduced in the presence of the herbicide metolachlor. This information along with our data suggests that biotic and abiotic stress can influence the overall allelopathic interaction with the benzoxazolinones.…”

Allelopathic Monoterpenes Interfere withArabidopsis thalianaCuticular Waxes and Enhance Transpiration

“…It is known that the reaction of plants to any allelochemical depends on the species and dose applied over time, but is also influenced by additional parameters such as biotic and abiotic stress and plant fitness. 46,47 Therefore, a long term exposure to relatively low concentrations may result in a damage of plants neighbored by monoterpene emitting species. From our results is concluded that the cuticle and the stomata, resulting in enhanced transpiration, are affected first when plants are exposed to allelopathic monoterpenes.…”