Plant secondary metabolites (SM) are widely used by humans in many ways (pharmacy, biotechnology etc.). For making their use even more effective, it is important to know the seasonality of these chemicals in plants and what affect those changes. Three Artemisia species (Artemisia annua, A. absinthium, A. vulgaris) were cultivated during one vegetation season (from April to September 2016). Plant growth parameters and the beginning of their generative stages were observed, and leaf samples were collected regularly. Samples of some plants were collected repeatedly. A generalist herbivore (migratory locust), was used as a proxy for studying changes in plant secondary metabolism during the vegetation season. The results proved presence of defence secondary metabolites in plants except A. vulgaris species where the role of SM in defence was not shown. Levels of SM changed nonlinearly during the vegetational season and were time-dependent. Plant size did not influence the levels of SM in plants. Levels of SM were low at the beginning of the experiment followed by rapid increase and remaining on maximal levels. The plants which lost their biomass repetitively grew slowly and bloomed later than the plants which were clipped only once. A delay trend showing seasonality of the plant SM was not proved. In...

O estudo fitoquímico de Peperomia oreophila revelou a presençca de duas lignanas furofurânicas (7R, 8R, 7R, 8R)-3,4,5-trimetóxi-3,4-metilenodioxi-5-metóxi- 8.8,7.O.9,7.O.9-lignana (1), (7R, 8R, 7R, 8R)-3,4,5-trimetóxi-3,4,5-trimetóxi- 8.8,7.O.9,7.O.9-lignana (2); as duas amidas (2E)-N-isobutil-3-(5-metóxi-7,8- benzodioxol-1-il)acrilamida (3), (2E)-N-isobutil-3-(3,4,5-trimetóxifenil)acrilamida (4), três derivados de acido cinâmico (2E)-3-(3,4,5-trimetóxifenil)acrilato de metila (5), (2Z)-3- (3,4,5-trimetóxifenil)acrilato de metila (6), (2E)-3-(5-metóxi-7,8-benzodioxol-1-il)acrilato de metila (7); os dois policetídeos fenólicos [(2E)-3,7-dimetilocta-2,6-dien-1-il]-5- metil-2-(3-metilbut-2-en-1-il)benzeno-1,3-diol (8) (inédita) e [(2E)-3,7-dimetilocta- 2,6-dien-1-il]-2,2,7-trimetil-2H-cromen-5-ol (9); de P. arifolia: o policetídeo fenólico [(2E)-3,7-dimetilocta-2,6-dien-1-il]-5-metil-2-(3-metilbut-2-en-1-il) benzeno-1,3-diol, isolada também de P. oreophila (10) (inédita); de P. urocarpa: o policetídeo fenólico 5- metil-2-[(2E,6E)-3,7,11-trimetildodeca-2,6,10-trien-1-il] benzeno-1,3-diol (11) e o ácido 2,4-dihidróxi-6-metil-3-[(2E,6E)-3,7,11-trimetildodeca-2,6,10-trien-1-il] benzóico, (12); de P. nitida: o fenilpropanoide apiol (1-alil-3,6-dimetóxi-10,11- benzodioxol) (13), os cromenos 7-hidróxi-2,2,5-trimetil-2H-cromeno-carboxilato de metila (14) e o 7-metóxi-2,2,5-dimetil-2H-cromeno-6-carboxilato de metila (15). O policetídeo 2-hidróxi-4,6-dimetóxiacetofenona, principal metabólito das folhas de P. glabella, teve sua biossíntese investigada utilizando-se como precursores o acetil-CoA e o malonil-CoA. Foram realizados estudos de otimização da atividade de policetídeo sintase (PKS) em função do pH, tempo de reação, temperatura e saturação de substratos, além de estudos da variação circadiana. Estudos de genes de PKS resultaram em amplificações cujo seqüenciamento poderá determinar a identidade dessas regiões e homologia entre as seqüências dessas Peperomias e a região KS do gene AviM de Streptomyces viridochromogenes que expressa o ácido orselínico / The phytochemical investigation carried out on Peperomia oreophila revealed the accumulation of two furofuran lignans (7R,8R,7R,8R)-3,4,5-trimethoxy-3,4- methylenedioxy-8.8, 7.O.9, 9.O.7-lignan (1), (7, 8R, 7R, 8)-3,4,5-trimethoxy-3,4,5- trimethoxy-8.8-7.O.9, 9.O.7-lignan (2); two amides (2´E)-N-isobutyl-3´-(5-methoxy-7,8- benzodioxol-1-yl) acrylamide (3), (2E)-N-isobutyl-3-(3,4,5-trimethoxyphenyl)acrylamide (4), three derivate cinâmic acid methyl (2E)-3-(3,4,5-trimethoxyphenyl)acrylate (5), methyl (2Z)-3-(3,4,5-trimethoxyphenyl)acrylate (6), methyl (2E)-3-(5-methoxy-7,8- benzodioxol-1-yl)acrylate (7); two phenolic polyketides [(2E)-3,7-dimethylocta-2,6- dien-1-yl]-5-methyl-2-(3-methylbut-2-en-1-yl)benzene-1,3-diol (8) (novel), [(2´E)-3´,7´- dimethylocta-2´,6´-dien-1-yl]-2,2,7-trimethyl-2H-chromen-5-ol (9); P. arifolia, two phenolic polyketide [(2E)-3,7-dimethylocta-2,6-dien-1-yl]-5-methyl-2-(3-methylbut-2- en-1-yl)benzene-1,3-diol, also isolated from P. oreophila (10) (novel); P. urocarpa, the two phenolic polyketides 5-methyl-2-[(2E,6E)-3,7,11-trimethyldodeca-2,6,10-trien-1- yl]benzene-1,3-diol (11) and 2,4-dihydroxy-6-methyl-3-[(2E,6E)-3,7,11-trimethyldodeca- 2,6,10-trien-1-yl]benzoic acid (12); P. nitida, the phenylpropanoid apiole 1-allyl-3,6- dimethoxy-10,11-benzodioxole (13); the chromenes methyl 7-hydroxy-2,2,5-trimethyl- 2H-chromene-6-carboxylate (14) and methyl 7-methoxy-2,2,5-trimethyl-2H-chromene-6- carboxylate (15). The polyketide 2-hydroxy-4,6-dimethoxyacetophenone, the major compound in P. glabella leaves, had its biosynthetic origin investigated using acetyl-CoA and malonyl-CoA as precursors. The enzymatic activity of polyketide synthase was optimized to pH, incubation time, temperatures and substrate saturation, in addition to the analysis of circadian variation activity. The amplifications of putative PKS genes was based on primers from AviM gene of Streptomyces viridochromogenes that express for orsellinic acid. The sequencing will enable the identification of such regions and also to study the homology to fungi PKS

Esta tese de doutorado descreve os estudos realizados para elucidar a biologia molecular da bioluminescência fúngica e sua relevância ecológica na natureza. A recente descoberta de que a luciferina fúngica é a 3-hidroxihispidina permitiu a caracterização do metabolismo secundário da fenilalanina nos genomas recém-sequenciados e transcriptomas de micélios das espécies luminescentes Panellus stipticus e Neonothopanus gardneri. Adicionalmente os genomas e transcriptomas de variedades não luminescente de P. stipticus e Lentinula edodes serviram como respectivos controles. Em geral, os genes envolvidos no metabolismo secundário da fenilalanina em amostras luminescentes tinham expressão igual ou superior àquela de espécies não luminescentes. Um agrupamento de genes relacionados com a biossíntese de fenilalanina foi encontrado em ambos os genomas luminescentes e não luminescentes de P. stipticus. A abundância de genes transcritos neste agrupamento foi semelhante para as espécies luminescentes e não luminescentes de P. stipticus, mas a policetídeo sintase tipo I em P. stipticus não luminescentes foi significativamente sub-regulada. Não foi encontrado agrupamento semelhante nos genomas de N. gardneri e L. edodes, sendo que os correspondentes homólogos estavam espalhados em diferentes loci. Extratos de fungos podem ser preparados in vitro, com a adição de 3-hidroxihispidina para produzir luz verde em abundância. A preparação de extratos proteicos de luciferase foi melhorada e a estrutura da luciferase, parcialmente purificada, foi investigada por espectrometria de massas. A presença de luciferase nos géis de purificação foi revelada usando-se luciferina e molécula similares à luciferina advindas de extratos de plantas. O nicho ecológico nas vizinhas de cogumelos bioluminescentes foi investigado de duas maneiras, armadilhas adesivas com cogumelos artificiais de acrílico, iluminados com luz LED verde e através da observação direta de cogumelos bioluminescentes com fotografia no infravermelho com lapso de tempo. Os estudos ecológicos foram conduzidos nos biomas da Mata Atlântica e da Mata dos Cocais, no Brasil. Baratas, aranhas, tesourinhas, grilo e vagalumes tec-tecs foram os animais mais comuns que interagiram com os cogumelos. Todos estes animais podem agir como dispersores de propágulos e, em alguns casos, como defensores dos cogumelos. / This PhD thesis describes the studies performed to elucidate the molecular biology of fungal bioluminescence and the ecological significance of the trait in the wild. The recent discovery that the fungal luciferin is 3-hydroxyhispidin has allowed for the characterization of phenylalanine secondary metabolism in the newly sequenced genomes and mycelium transcriptomes of luminescent Panellus stipticus and Neonothopanus gardneri, additionally the genomes and transcriptomes of a non-luminescent variety of P. stipticus and Lentinula edodes served as respective controls. In general the genes involved in phenylalanine secondary metabolism had greater or equal expression in luminescent samples than non luminescent. A cluster of genes related to the secondary metabolism of phenylalanine was found in both luminescent and non luminescent P. stipticus genomes. Transcript abundance of genes in this cluster was similar in both luminescent and non-luminescent Panellus stipticus, but the type I polyketide synthase in non luminescent Panellus stipticus was significantly down regulated. A similar gene cluster in the N. gardneri and L. edodes genomes was absent with corresponding homologues scattered at different genomic loci. Cell free fungal extracts can be combined in vitro with the addition of 3-hydroxyhispidin to produce abundant green light. Preparation of proteinaceous luciferase extracts was improved and partially purified luciferase samples were investigated by mass spectrometry. The presence of luciferase in the separation gel was also evidenced by using luciferin and luciferin-like molecules from plant extracts. The ecological niche surrounding bioluminescent mushrooms was investigated through two main means, glue traps with acrylic mushroom facsimiles that were internally illuminated with green LED lights and direct observation of bioluminescent mushrooms with infrared time lapse photography. Ecological studies were performed in the Atlantic rainforest (Mata Atlântica) and transitional Coconut Palm forest (Mata dos Cocais) biomes of Brazil. Cockroaches, spiders, earwigs, crickets, and luminescent click beetles were the most common animal interacting with mushrooms. All of these animals may be acting as fungal propagule dispersers and in some cases defense of the mushroom.

Estudos realizados em 1979 por Kelecom e Kanengiesser mostraram que extratos brutos obtidos a partir de amostras da esponja marinha Aplysina fulva não possuíam derivados bromados. Estes foram resultados inesperados, uma vez que esponjas pertencentes à ordem Verongida são conhecidos produtores de metabólitos derivados da dibromotirosina. O presente projeto teve como meta a investigação química de extratos obtidos de duas amostras de A. fulva, sendo uma coletada em São Sebastião (SP) e a outra em Angra dos Reis (RJ), objetivando verificar a ocorrência de derivados da bromotirosina e uma possível variabilidade química dependendo da distribuição geográfica das esponjas. Sete derivados da dibromotirosina foram isolados das duas amostras de Aplysina fulva: quatro compostos da amostra de Angra dos Reis e três da de São Sebastião. As estruturas dos compostos foram identificadas por análises espectroscópicas (como IV, UV, RMN 1H, RMN 13C, HMQC, COSY, HMBC) e de espectrometria de massas, e ainda por comparação com dados da literatura. Os resultados obtidos confirmaram que os derivados da dibromotirosina são bons marcadores quimiotaxonômicos para as esponjas da Ordem Verongida. Além disso, a variabilidade química observada para a A. fulva parece ser influência de fatores abióticos e bióticos como sazonalidade, disponibilidade de nutrientes, ou associação com diferentes micro-organismos. / Studies developed in 1979 by Kelecom and Kanengiesser showed that crude extracts obtained from samples of the marine sponge Aplysina fulva were devoid of bromotyrosine derivatives. These results were rather unexpected, since sponges belonging to the Order Verongida are well-known producers of bromotyrosine-derived metabolites. The present project aimed the chemical investigation of crude extracts obtainded from two samples of A. fulva, one collected at São Sebastião (SP) and the second from Angra dos Reis (RJ), in order to verify the occurrence of bromotyrosine derivatives and a possible chemical variability depending on the geographical distribution of the sponge. Seven bromoyrosine derivatives have been isolated from the two samples of A. fulva: four compounds from the Angra dos Reis sample and three from the São Sebastião sample. The structures of the compounds have been established by spectroscopic analysis, (including IV, UV, RMN 1H, RMN 13C, HMQC, COSY, HMBC) and mass spectrometry, as well as by comparison with literature data. The results obtained confirmed that bromotyrosine derivatives are good chemotaxonomic markers for sponges of the Order Verongida. Moreover, it appears that chemical variability of A. fulva may be influenced by abiotic and biotic factors, such as seasonality, nutrients availability, or association with distinct micro-organisms.

Made available in DSpace on 2014-08-20T13:42:06Z (GMT). No. of bitstreams: 1 Dissertacao_Gabrie_Olle_ Dalmazo.pdf: 526235 bytes, checksum: 5e78165179f8f9e3164e0269bd617ab9 (MD5) Previous issue date: 2011-02-28 / The tropane alkaloids (TA) pathway has a branch-point controlled by the enzymes tropinone reductase 1 and 2 (TR1 and TR2). Tropinone is the common substrate for these enzymes and is reduced either by TR1 to form tropine, hyoscyamine and scopolamine or by TR2 to form pseudotropine and calystegines. Hyoscyamine and scopolamine are largely used in medicine as anticholinergic, antiemetic, parasympatholytic and anaesthetic. Calystegines mimic different sugars and are potent and specific inhibitors of glucosidases. The function of hyoscyamine, scopolamine and calystegines in the plants is not fully understood. Recent studies suggest that they are involved in the plant defense against pathogens. Regulation of TA biosynthesis in planta has attracted interest not only in view of its applications in the pharmaceutical industry, but also in respect to human nutrition and plant physiology. In the present study a virus-based transgenic approach devised to induce PTGS of tr1 and tr2 in whole transformed Hyoscyamus muticus plants is evaluated. It was observed that a significant reduction in transcript accumulation for tr2 caused a tremendous increase in transcript accumulation for tr1. / Um ponto de bifurcação na rota metabólica de tropano alcalóides (TA) é controlado pelas enzimas tropinona redutase 1 e 2 (TR1 e TR2). Tropinona, o substrato comum para estas enzimas, é reduzido por TR1 para formar tropina, hiosciamina e escopolamina ou por TR2 para formar pseudotropine e calisteginas. Hiosciamina e escopolamina são largamente utilizadas em medicina como anticolinérgicos, antieméticos, parassimpatolíticos e anestésicos. Calisteginas têm estrutura molecular semelhante a açúcares e são potentes inibidores específicos de glucosidases. A função dos alcalóides hiosciamina, escopolamina e calisteginas em plantas não é completamente entendida. Estudos recentes sugerem o envolvimento destes alcalóides na defesa da planta contra patógenos. A regulação da biossíntese de TA na planta tem atraído interesse não apenas quanto à aplicação na indústria farmacêutica, mas também com respeito à nutrição humana e fisiologia de plantas. No presente estudo avaliou-se uma estratégia transgênica, baseada em vírus, para induzir o silenciamento gênico pós-transcricional de tr1 e tr2 em plantas de Hyoscyamus muticus L. Observou-se que reduções significativas no acúmulo de transcritos para tr2 causaram um tremendo aumento no acúmulo de transcritos para tr1.

Botrytis cinerea est un champignon nécrotrophe et polyphage capable de provoquer la pourriture grise sur plusieurs centaines d’espèces végétales. Les pertes engendrées par cette maladie sont importantes à travers le monde notamment sur des espèces économiquement importantes comme la tomate, la fraise ou encore la vigne. Parmi les facteurs de virulence identifiés chez B. cinerea se trouvent deux toxines non-hôte spécifiques. Il s'agit du sesquiterpène botrydial et du polycétide acide botcinique. Même si leur rôle redondant dans la nécrotrophie a été démontré, les mécanismes qui gouvernent l’expression des clusters responsables de leur synthèse (respectivement BOT et BOA) restent inconnus. Dans ce contexte, l’objectif de mon projet de thèse était de caractériser les différents mécanismes qui régulent le métabolisme secondaire chez B. cinerea. Je me suis particulièrement intéressé aux clusters BOT et BOA ainsi qu’à un troisième cluster (PKS7) qui, d’après le phénotype d’un mutant d’insertion (ADN-T), pourrait être impliqué dans la nécrotrophie. Grâce à la disponibilité du nouvel assemblage du génome de la souche modèle B05.10, un gène candidat codant un facteur de transcription (FT) putatif a pu être identifié à proximité du cluster BOT. La caractérisation de ce gène a permis de démontrer le rôle majeur de la protéine (BcBot6) dans l’activation des gènes Bcbot et la production subséquente de botrydial. De même, la caractérisation de Bcboa13, un gène codant un FT putatif présent au sein du cluster BOA, a permis de démontrer le rôle de régulateur positif de BcBoa13 envers les gènes Bcboa. A la différence des clusters BOT et BOA, le cluster PKS7 ne contient pas de gène codant pour un potentiel FT spécifique. Afin de confirmer le rôle du métabolite putatif produit par ce cluster et d’identifier sa structure chimique, l’inactivation du gène clé codant une PKS-NRPS (Bcpks7) a été réalisée et des analyses métaboliques ont été initiées. Finalement, la présence au sein des clusters BOT et BOA de nombreux transposons ayant subi des mutations de type RIP (Repeat-Induced Point mutations) ainsi que la position sub-télomérique des clusters BOA et PKS7 nous a amené à nous intéresser au rôle de la structure chromatinienne dans la régulation de ces clusters. Dans ce cadre, trois mutants délétés dans des gènes codant des modificateurs chromatiniens putatifs (les histones méthyltransférases BcDim-5 et BcKmt6 et la protéine hétérochromatinienne BcHp1) ont été générés. L’expression des gènes clés des clusters BOT, BOA et PKS7 chez les mutants Bcdim-5, Bchp1 et Bckmt6 suggère que différents mécanismes chromatiniens interviennent pour le contrôle des clusters BOT et BOA d’une part et du cluster PKS7 d’autre part. L’ensemble des résultats obtenus pendant cette thèse apporte une contribution majeure à la compréhension des mécanismes de régulation spécifiques mais aussi de ceux en lien avec la structure chromatinienne de la production de métabolites phytotoxiques impliqués dans la nécrotrophie chez B. cinerea. / Botrytis cinerea is a necrotrophic polyphagous fungus able to induce the gray mold disease on hundreds of plant species. The resulting losses are important worldwide notably on economically important crops such as tomato, strawberry or grapevine. Among the virulence factors identified in B. cinerea stand two non-host specific toxins: the sesquiterpene botrydial and the polyketide botcinic acid. Although their redundant role in necrotrophy has been shown, the mechanisms governing the clusters responsible for their synthesis (respectively BOT and BOA) remain unknown. In this context, the aim of my PhD project was to characterize the different mechanisms that regulate secondary metabolism in B. cinerea. I particularly focused on BOT and BOA clusters as well as on a third one (PKS7) which, according to the phenotype of an insertion-based mutant (T-DNA), could be involved in necrotrophy. Thanks to the newly assembled genome of the B05.10 wild type strain, a candidate gene encoding a putative transcription factor (TF) could be identified near the BOT cluster. The characterization of this gene allowed pointing out the major role of the protein (BcBot6) in the activation of Bcbot genes and in the subsequent botrydial production. Similarly, the characterization of Bcboa13, a putative TF-encoding gene present into the BOA cluster, allowed demonstrating the positive regulatory role of BcBoa13 on Bcboa genes. Unlike the BOT and BOA clusters, the PKS7 one does not contain any putative TF-encoding gene. In order to confirm the role of the putative metabolite produced by this cluster and to identify its chemical structure, the inactivation of the PKS-NRPS key enzyme-encoding gene (Bcpks7) was conducted and metabolic analyses were initiated. Finally, the presence of many RIP(Repeat-Induced Point mutations)-inactivated transposons within BOT and BOA clusters as well as the subtelomeric location of BOA and PKS7 clusters raised our interest about the role of chromatin structure on those clusters regulation. In this context, three mutants inactivated into putative chromatin modifiers encoding-genes (the histone methyltransferases BcDim-5 and BcKmt6 and the heterochromatin protein BcHp1) were generated. The expression analysis of the key genes of the BOT, BOA and PKS clusters suggests different chromatin-based mechanisms that intervene for the BOT and BOA cluster on one side and on the PKS7 cluster on another. Altogether, the results generated during this PhD project are a major contribution to the comprehension of pathway-specific as well as chromatin-based mechanisms that regulate the production of necrotrophy-involved phytotoxins by B. cinerea.

Flavonoids are secondary metabolites that have significant roles in plant defense and human nutrition. Glucosyltransferases (GTs) catalyze the transfer of sugars from high energy sugar donors to other substrates. Several different secondary product GTs exist in the tissues of grapefruit making it a model plant for studying their structure and function. The goal of this investigation was to determine the expression patterns of seven putative secondary product GTs during grapefruit growth and development by quantifying mRNA expression levels in the roots, stems, leaves, flowers, and mature fruit to establish whether the genes are expressed constitutively or if one or more could be expressed in a tissue specific manner and/or developmentally regulated. Six growth stages were defined from which RNA was extracted, and expression levels were quantified by standardized densitometry of gene-specific RT-PCR products. Results show that there were variable degrees of PGT expression in different tissues and at different developmental stages. These results add to the growing knowledge base of dynamics of expression and potential regulation of secondary metabolism in Citrus paradisi.

Flavonoids are secondary metabolites that have significant roles in plant defense and human nutrition. Glucosyltransferases (GTs) transfer sugars from high energy sugar donors to other substrates. Several different kinds of flavonoid GTs exist in the tissues of grapefruit making it a model plant for studying their structure and function. The goal of this investigation is to determine the expression patterns of 7 putative secondary product GTs during grapefruit growth and development by quantifying mRNA expression levels in the roots, stems, leaves, and flowers. This research was designed to test the hypothesis that these 7 GT's are expressed constitutively. Alternatively, one or more could be expressed in a tissue-specific manner and/or developmentally regulated. Six growth stages were defined. Findings show that there were variable degrees of PGT expression. Therefore, results were more consistent with the alternative hypothesis that putative secondary product GT expression was tissue specific and/or developmentally regulated.

No description available.

<p>Bacterial small RNAs have emerged as a class of molecules having important regulatory roles. Accumulating numbers of <em>cis</em>-encoded sRNAs (antisense RNAs) have been recently discovered to be transcribed from the chromosomal DNA of many bacterial species, including the streptomycetes. Here, we investigate potential regulatory roles for two <em>S. coelicolor</em> antisense RNAs, scr4677 and α-abeA.</p> <p>The scr4677 antisense RNA is transcribed from the intergenic region between <em>SCO4676</em> (a gene encoding a conserved protein of unknown function) and <em>SCO4677</em>, encoding a regulatory protein with proposed anti-sigma factor activity. Transcription profiling revealed that scr4677 may not only interact with <em>SCO4676</em> mRNA but also with <em>SCO4677-4676</em> read-through transcripts. Our study suggested that scr4677 functioned to destabilize <em>SCO4676</em> mRNA, at the same time that it stabilized the <em>SCO4677-4676</em> read-through transcript. The potential role for scr4677 in destabilizing <em>SCO4676</em> mRNA was not mediated by the double stranded ribonuclease RNase III. Genetic analysis showed <em>scr4677</em> transcription was affected by SCO4677, and the transcription was apparently dependent on an unknown protein binding to the <em>SCO4676 </em>coding sequence.</p> <p>A second independent study focused on investigating the regulation of a previously uncharacterized genetic region, <em>SCO3287-3290</em>, since renamed <em>abeABCD</em>. This region contains an antisense RNA (α-abeA)-encoding gene, and is adjacent to the downstream <em>SCO3291</em> (<em>abeR</em>) gene, which encodes a putative regulatory protein. Genetic analysis revealed that overexpression of <em>abeR </em>or <em>abeABCD</em> stimulated the production of the blue-pigmented antibiotic actinorhodin, and deletion of <em>abeR</em> impaired actinorhodin production. Transcription analysis revealed the <em>abe</em> genes (including α-<em>abeA</em>) to be subject to multiple levels of regulation. We found an internal promoter within the <em>abeA</em> coding sequence and that required AbeR for expression. Furthermore, biochemical experiments demonstrated that AbeR regulated <em>abeBCD</em> directly, by binding to four heptameric repeats in its promoter region. The expression of α-<em>abeA</em> and other <em>abe</em> genes were differentially affected by RNase III.</p> / Doctor of Science (PhD)