Thesis (M. Sc.) -- Lincoln University, 2010. / Also available via the World Wide Web.

Thesis (doctoral)--University of Helsinki, 2004. / Includes bibliographical references. Also available on the World Wide Web.

Diss.Teknillinen korkeakoulu, 2006.

Thèse (M.Sc.)--Université Laval, 1996. / Bibliogr.: f. 57-68. Publié aussi en version électronique.

Trichoderma species are ubiquitous soil saprotrophs and well-characterized biological control agents. Certain strains have also been shown to stimulate plant growth through the production of bioactive secondary metabolites, and are therefore receiving increased attention as natural plant growth stimulants. Previous research at the University of Exeter (Ryder et al. (2012) Microbiology 158, 84-97) has shown that the Plant Growth Promotion activity of a biocontrol strain of Trichoderma hamatum (strain GD12) can be dramatically enhanced by targeted mutation of the N-acetyl-β-D-glucosaminidase-encoding gene nag. However, due to the loss in chitinase activities, the mutant (ΔThnag::hph) displays loss of saprotrophic competitiveness and reduced fitness as a biocontrol agent. We set out to investigate how we can use genetic manipulation to improve strain GD12 in the context of biological control and plant growth promotion. We approached this by firstly sequencing the whole genome of GD12 and then using the information available from this to produce a targeted deletion mutant in the GD12 background disrupting one of the most down regulated proteins in the ΔThnag::hph, a branched chain amino acid transaminase (bcat), implicated in the production of secondary metabolites. Secondly, we aimed to engineer hyper-secretion and enhanced PGP activities in GD12 without impairing biocontrol activity. Over-expression of the S. cerevisiae gene dolichol-phosphate mannose synthase (dpm1) in T. reesei leads to altered cell wall architecture and increased secretory potential. Using the constitutive promoter ToxA, we over-expressed the dpm1 gene in T. hamatum GD12 and assessed its effects on the biocontrol and PGP activities of the fungus. The data presented herein, shows, that bcat deletion in T. hamatum GD12 results in a detrimental effect of germination of lettuce seedlings grown in the presence of ∆Thbcat::hph. We show that single copy insertions of ToxA-dpm1 leads to improved PGP activities, while biocontrol fitness is unaffected. However, while multiple copy insertions similarly lead to enhanced PGP, such strains display impaired biocontrol of soil-borne pathogens such as the plurivorous damping-off pathogen Sclerotinia sclerotiorum. This work demonstrates that while significant improvements in crop productivity can be achieved through genetic modification of the beneficial rhizosphere fungus T. hamatum GD12, it can have important consequences for other aspects of its biology and ecology and competence as a soil-borne microorganism.

Trichoderma spp. são fungos benéficos que após interagir com as raízes melhora o vigor das plantas. Trichoderma spp. produzem uma variedade de MAMPs (Padrões Moleculares Associados a Micro-organismos) que estimulam a indução de resistência (IR) em plantas. A IR por Trichoderma spp. pode aumentar a resistência contra patógenos através das respostas mediadas por ácido salicílico (AS), ácido jasmônico (JA), etileno (ET). Estas respostas reguladas são antagônicas entre as diferentes vias de sinalização de defesa relacionadas à JA/ ET e AS, sensibilizando a planta para uma resistência melhorada contra patógenos. Neste estudo utilizamos um sistema entre três componentes Solanum lycopersicum, Trichoderma harzianum e Alternaria alternata. A sinalização molecular envolvido durante a supressão da doença por T. harzianum foi analisado nas plantas de tomate cv. Micro-Tom subsequente à infecção por A. alternata. As vias de sinalização de AS, JA e ET foram exploradas durante IR por T. harzianum. À aplicação dos esporos de T. harzianum nas raízes das plantas de tomate aumentou a resistência contra A. alternata causador da mancha foliar da cultura. O intervalo de 15 dias entre a aplicação de T. harzianum e de A. alternata foi suficiente para suprimir os sintomas causados por A. alternata no tomate. A severidade da doença foi estimada 96 horas após inoculação do patógeno desafiante. A quantificação do DNA por qPCR foi utilizado para verificar as diferenças da biomassa do patógeno. O resultado obtido da quantidade de DNA de A. alternata foi 74 vezes menor nas plantas previamente tratadas com T. harzianum isolado Th1 em comparação com as plantas não tratadas com Th 1. O tratamento com os hormônios etileno e metil jasmonato indicou que as vias do JA e ET estão parcialmente relacionadas com a suscetibilidade à A. alternata em plantas de tomate. Foi avaliado o fenótipo de IR de plantas de tomate silenciadas para o gene de fator de resposta de ET. A análise do desenvolvimento dos sintomas demonstrou que a IR por T. harzianum não envolveu a resposta do ET. Finalmente, análise da expressão gênica indica que a resistência induzida por T. harzianum é controlada pelo aumento da biossíntese do JA combinado com a diminuição da sinalização de resposta do AS e ET. / Trichoderma spp. are beneficial fungi that after interacting with the roots improves plant health. Trichoderma spp. produce a variety of MAMPs (Associated Molecular Patterns Micro-organisms) that stimulate the induction of resistance (IR) in plants. The IR by Trichoderma spp. can increase resistance against pathogens mediated through salicylic acid (SA), jasmonic acid (JA), ethylene (ET) responses. These responses regulated are antagonistic between different defense signaling pathways related to JA/ET and AS, sensitizing the plant for enhanced resistance against pathogens. In this study we used a system of three components Solanum lycopersicum, Trichoderma harzianum and Alternaria alternata. The molecular signaling involved during disease suppression by T. harzianum was analyzed in tomato plants cv. Micro-Tom subsequent to infection by A. alternata. The signaling pathways of SA, JA and ET have been explored for IR T. harzianum. In the application of spores of T. harzianum in the roots of tomato plants increased resistance against A. alternata causing leaf spot of culture. The 15 day interval between application of T. harzianum and A. alternata was sufficient to suppress symptoms caused by A. alternata in tomato. The effect of IR elicited by T. harzianum was from his association with the roots of tomato for 15 days. Disease severity was estimated 96 hours after inoculation the challenge pathogen. DNA quantification by qPCR was used to determine differences in biomass of the pathogen. The result of the amount of DNA of A. alternata was 74 times lower in treated plants T. harzianum isolated Th1 compared with plants not treated with Th 1. Treatment with ethylene and methyl jasmonate indicated that the hormones JA and ET pathways are partially related to susceptibility to A. alternata in tomato plants. IR phenotype of tomato plants silenced for gene ET response factor was evaluated. The analysis of the development of symptoms demonstrated that IR by T. harzianum did not involve the response of ET. Finally, gene expression analysis indicates that IR by T. harzianum is controlled by increasing the biosynthesis of JA combined with the decrease in the response signaling SA and ET.

No description available.

Made available in DSpace on 2016-02-05T18:29:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-06-15. Added 1 bitstream(s) on 2016-02-05T18:33:29Z : No. of bitstreams: 1 000856459.pdf: 3178267 bytes, checksum: 2cf663dcd224c489e1ad9c983349b072 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Fungus-growing attine ants forage diverse substrates to grow mutualistic fungi for food. In addition to the fungal partner, colonies of these insects harbor a rich microbiome composed of bacteria, filamentous fungi and yeasts. Previous studies investigated ecological aspects of filamentous fungi in gardens of leaf-cutter ants and reported some Trichoderma species; however, no studies systematically addressed the putative association of Trichoderma species with attine ants, especially in non-leafcutter ants. Here, a total of 68 strains of Trichoderma preserved in our collection were analyzed using three molecular markers (ITS, tef1 and rpb2). In addition, 30 out of 68 strains were also morphologically examined. The strains correspond to samples collected from leaf-cutter and non-leafcutter ants in 12 points from four states in Brazil and two points in Texas (USA), comprising the largest sampling carried out so far for Trichoderma in attine ant environment. Our results revealed the richness of Trichoderma in this environment, since we found 19 Trichoderma species, including three new species described in the present work (T. attinis, T. texana and T. longifialidicum). Moreover, we show that all 68 strains grouped within different clades across the Trichoderma phylogeny, which are identical or closely related to strains derived from several other environments, supporting for a transient nature of the genus Trichoderma in attine ant colonies. The discovery of three new species suggests that the dynamic foraging behavior of these insects might be responsible for accumulation of transient fungi into their colonies, which might hold several fungal taxa still unknown for science

Orientador: André Rodrigues / Banca: Derlene Attili de Angelis / Banca: Maisa Ciampi Guillardi / Abstract: Fungus-growing "attine" ants forage diverse substrates to grow mutualistic fungi for food. In addition to the fungal partner, colonies of these insects harbor a rich microbiome composed of bacteria, filamentous fungi and yeasts. Previous studies investigated ecological aspects of filamentous fungi in gardens of leaf-cutter ants and reported some Trichoderma species; however, no studies systematically addressed the putative association of Trichoderma species with attine ants, especially in non-leafcutter ants. Here, a total of 68 strains of Trichoderma preserved in our collection were analyzed using three molecular markers (ITS, tef1 and rpb2). In addition, 30 out of 68 strains were also morphologically examined. The strains correspond to samples collected from leaf-cutter and non-leafcutter ants in 12 points from four states in Brazil and two points in Texas (USA), comprising the largest sampling carried out so far for Trichoderma in attine ant environment. Our results revealed the richness of Trichoderma in this environment, since we found 19 Trichoderma species, including three new species described in the present work (T. attinis, T. texana and T. longifialidicum). Moreover, we show that all 68 strains grouped within different clades across the Trichoderma phylogeny, which are identical or closely related to strains derived from several other environments, supporting for a transient nature of the genus Trichoderma in attine ant colonies. The discovery of three new species suggests that the dynamic foraging behavior of these insects might be responsible for accumulation of transient fungi into their colonies, which might hold several fungal taxa still unknown for science / Mestre

Trichoderma spp. são fungos benéficos que após interagir com as raízes melhora o vigor das plantas. Trichoderma spp. produzem uma variedade de MAMPs (Padrões Moleculares Associados a Micro-organismos) que estimulam a indução de resistência (IR) em plantas. A IR por Trichoderma spp. pode aumentar a resistência contra patógenos através das respostas mediadas por ácido salicílico (AS), ácido jasmônico (JA), etileno (ET). Estas respostas reguladas são antagônicas entre as diferentes vias de sinalização de defesa relacionadas à JA/ ET e AS, sensibilizando a planta para uma resistência melhorada contra patógenos. Neste estudo utilizamos um sistema entre três componentes Solanum lycopersicum, Trichoderma harzianum e Alternaria alternata. A sinalização molecular envolvido durante a supressão da doença por T. harzianum foi analisado nas plantas de tomate cv. Micro-Tom subsequente à infecção por A. alternata. As vias de sinalização de AS, JA e ET foram exploradas durante IR por T. harzianum. À aplicação dos esporos de T. harzianum nas raízes das plantas de tomate aumentou a resistência contra A. alternata causador da mancha foliar da cultura. O intervalo de 15 dias entre a aplicação de T. harzianum e de A. alternata foi suficiente para suprimir os sintomas causados por A. alternata no tomate. A severidade da doença foi estimada 96 horas após inoculação do patógeno desafiante. A quantificação do DNA por qPCR foi utilizado para verificar as diferenças da biomassa do patógeno. O resultado obtido da quantidade de DNA de A. alternata foi 74 vezes menor nas plantas previamente tratadas com T. harzianum isolado Th1 em comparação com as plantas não tratadas com Th 1. O tratamento com os hormônios etileno e metil jasmonato indicou que as vias do JA e ET estão parcialmente relacionadas com a suscetibilidade à A. alternata em plantas de tomate. Foi avaliado o fenótipo de IR de plantas de tomate silenciadas para o gene de fator de resposta de ET. A análise do desenvolvimento dos sintomas demonstrou que a IR por T. harzianum não envolveu a resposta do ET. Finalmente, análise da expressão gênica indica que a resistência induzida por T. harzianum é controlada pelo aumento da biossíntese do JA combinado com a diminuição da sinalização de resposta do AS e ET. / Trichoderma spp. are beneficial fungi that after interacting with the roots improves plant health. Trichoderma spp. produce a variety of MAMPs (Associated Molecular Patterns Micro-organisms) that stimulate the induction of resistance (IR) in plants. The IR by Trichoderma spp. can increase resistance against pathogens mediated through salicylic acid (SA), jasmonic acid (JA), ethylene (ET) responses. These responses regulated are antagonistic between different defense signaling pathways related to JA/ET and AS, sensitizing the plant for enhanced resistance against pathogens. In this study we used a system of three components Solanum lycopersicum, Trichoderma harzianum and Alternaria alternata. The molecular signaling involved during disease suppression by T. harzianum was analyzed in tomato plants cv. Micro-Tom subsequent to infection by A. alternata. The signaling pathways of SA, JA and ET have been explored for IR T. harzianum. In the application of spores of T. harzianum in the roots of tomato plants increased resistance against A. alternata causing leaf spot of culture. The 15 day interval between application of T. harzianum and A. alternata was sufficient to suppress symptoms caused by A. alternata in tomato. The effect of IR elicited by T. harzianum was from his association with the roots of tomato for 15 days. Disease severity was estimated 96 hours after inoculation the challenge pathogen. DNA quantification by qPCR was used to determine differences in biomass of the pathogen. The result of the amount of DNA of A. alternata was 74 times lower in treated plants T. harzianum isolated Th1 compared with plants not treated with Th 1. Treatment with ethylene and methyl jasmonate indicated that the hormones JA and ET pathways are partially related to susceptibility to A. alternata in tomato plants. IR phenotype of tomato plants silenced for gene ET response factor was evaluated. The analysis of the development of symptoms demonstrated that IR by T. harzianum did not involve the response of ET. Finally, gene expression analysis indicates that IR by T. harzianum is controlled by increasing the biosynthesis of JA combined with the decrease in the response signaling SA and ET.