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Carot-4-en-9,10-diol, a conidiation-inducing sesquiterpene diol produced by Trichoderma virens PS1-7 upon exposure to chemical stress from highly active iron chelators.

ABSTRACT: To screen biocontrol agents against Burkholderia plantarii, the causative agent of rice seedling blight, we employed catechol, an analog of the virulence factor tropolone, to obtain chemical stress-resistant microorganisms. The fungal isolate PS1-7, identified as a strain of Trichoderma virens, showed the highest resistance to catechol (20 mM) and exhibited efficacy as a biocontrol agent for rice seedling blight. During investigation of metabolic traits of T. virens PS1-7 exposed to catechol, we found a secondary metabolite that was released extracellularly and uniquely accumulated in the culture. The compound induced by chemical stress due to catechol was subsequently isolated and identified as a sesquiterpene diol, carot-4-en-9,10-diol, based on spectroscopic analyses. T. virens PS1-7 produced carot-4-en-9,10-diol as a metabolic response to tropolone at concentrations from 0.05 to 0.2 mM, and the response was enhanced in a dose-dependent manner, similar to its response to catechol at concentrations from 0.1 to 1 mM. Some iron chelators, such as pyrogallol, gallic acid, salicylic acid, and citric acid, at 0.5 mM also showed activation of T. virens PS1-7 production of carot-4-en-9,10-diol. This sesquiterpene diol, formed in response to chemical stress, promoted conidiation of T. virens PS1-7, suggesting that it is involved in an autoregulatory signaling system. In a bioassay of the metabolic and morphological responses of T. virens PS1-7, conidiation in hyphae grown on potato dextrose agar (PDA) plates was either promoted or induced by carot-4-en-9,10-diol. Carot-4-en-9,10-diol can thus be regarded as an autoregulatory signal in T. virens, and our findings demonstrate that intrinsic intracellular signaling regulates conidiation of T. virens.

SUBMITTER: Wang M

PROVIDER: S-EPMC3592238 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Carot-4-en-9,10-diol, a conidiation-inducing sesquiterpene diol produced by Trichoderma virens PS1-7 upon exposure to chemical stress from highly active iron chelators.

Wang Mengcen M Hashimoto Makoto M Hashidoko Yasuyuki Y

Applied and environmental microbiology 20130111 6

To screen biocontrol agents against Burkholderia plantarii, the causative agent of rice seedling blight, we employed catechol, an analog of the virulence factor tropolone, to obtain chemical stress-resistant microorganisms. The fungal isolate PS1-7, identified as a strain of Trichoderma virens, showed the highest resistance to catechol (20 mM) and exhibited efficacy as a biocontrol agent for rice seedling blight. During investigation of metabolic traits of T. virens PS1-7 exposed to catechol, we ...[more]

PMID: 23315728

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Project description:BackgroundThe tropolone-tolerant Trichoderma virens PS1-7 is a biocontrol agent against Burkholderia plantarii, causative of rice seedling blight. When exposed to catechol, this fungus dose-dependently produced carot-4-en-9,10-diol, a sesquiterpene-type autoregulatory signal molecule that promotes self-conidiation of T. virens PS1-7 mycelia. It was, however, uncertain why T. virens PS1-7 attenuates the symptom development of the rice seedlings infested with B. plantarii.Methodology/principal findingsTo reveal the antagonism by T. virens PS1-7 against B. plantarii leading to repression of tropolone production in a coculture system, bioassay-guided screening for active compounds from a 3-d culture of T. virens PS1-7 was conducted. As a result, carot-4-en-9,10-diol was identified and found to repress tropolone production of B. plantarii from 10 to 200 µM in a dose-dependent manner as well as attenuate virulence of B. plantarii on rice seedlings. Quantitative RT-PCR analysis revealed that transcriptional suppression of N-acyl-L-homoserine lactone synthase plaI in B. plantarii was the main mode of action by which carot-4-en-9,10-diol mediated the quorum quenching responsible for repression of tropolone production. In addition, the unique response of B. plantarii to carot-4-en-9,10-diol in the biofilm formed in the static culture system was also found. Although the initial stage of B. plantarii biofilm formation was induced by both tropolone and carot-4-en-9,10-diol, it was induced in different states. Moreover, the B. plantarii biofilm that was induced by carot-4-en-9,10-diol at the late stage showed defects not only in matrix structure but also cell viability.Conclusions/significanceOur findings demonstrate that carot-4-en-9,10-diol released by T. virens PS1-7 acts as an interkingdom cell-to-cell signaling molecule against B. plantarii to repress tropolone production and induces pseudo-biofilm to the cells. This observation also led to another discovery that tropolone is an autoregulatory cell-to-cell signaling molecule of B. plantarii that induces a functional biofilm other than a simple B. plantarii virulence factor.

Project description:Combating the action of plant pathogenic microorganisms by antagonistic or mycoparasitic fungi has been announced as an attractive biological alternative to the use of chemical fungicides since more than 20 years, and gains additional importance in current trends to environmentally friendly agriculture. Taxa of the fungal genus Hypocrea/Trichoderma (Ascomycota, Hypocreales, Hypocreaceae) contain prominent examples of such biocontrol agents, because they not only antagonize plant-pathogenic fungi, but are also often rhizosphere competent and can enhance plant growth. Identification of the primary factors that regulate the mycoparasitic behaviour and metabolic activities related to it will therefore allow the full ecological significance of this trait to be explored. We performed the analysis of the genome sequence from two mycoparasitic and rhizosphere competent Trichoderma spp. – T. atroviride and T. virens – and compare it to that of the saprophyte T. reesei. The predicted gene inventory of the T. atroviride and T.virens genome, therefore, points to previously unknown mechanisms operating during biocontrol of plant pathogens. The availability of these genomes provides a unique opportunity to develop a deeper understanding of the processes fundamental to mycoparasitism and its application for the breeding of improved biocontrol strains for plant protection. To investigate the potential role in mycoparasitism, microarrays were used to examine T. virens transcript levels when confronted with a potential prey (the plant pathogen Rhizoctonia solani) before contact, during first physical contact and during overgrowth of the host. The study presented here is the result of this analysis. Two biological pools by condition against a common reference control each sample hybridized in dye switch. On the two biological replicates we apply on the pretreated results the linear modeling approach implemented by lmFit and the empirical Bayes statistics implemented by eBayes from the limma R package (Smyth 2004). For mycoparasitism confrontation assays T. virens was grown on potato dextrose agar plates (BD Dicfo, Franklin Lakes, NJ, USA), covered with cellophane, in constant light at 25°C and harvested when the mycelia were ca. 5 mm apart (before contact), at contact of the mycelia and after T. virens had overgrown the host fungus Rhizoctonia solani by ca. 5 mm (after contact). As control T. virens was confronted with itself and harvested at contact. Peripheral hyphal zones from each confrontation stage were harvested and shock frozen in liquid nitrogen. Mycelia were ground to a fine powder under liquid nitrogen and total RNA was isolated using the guanidinium thiocyanate method (Sambrook, 2001).

Dataset Information

Carot-4-en-9,10-diol, a conidiation-inducing sesquiterpene diol produced by Trichoderma virens PS1-7 upon exposure to chemical stress from highly active iron chelators.

Publications

Carot-4-en-9,10-diol, a conidiation-inducing sesquiterpene diol produced by Trichoderma virens PS1-7 upon exposure to chemical stress from highly active iron chelators.

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