Transformation vector with mutated psbA gene and selective aadA gene was created and transferred into Nicotiana tabacum living cells using Biolistic bombardment. Due to homologous recombination, transformed plant lineage carrying D1-A209, D1-C-212 instead of D1-S209, D1-S212 in D1 protein in PS II was obtained. Seeds from transformed plant were harvested and homoplasmy of the first generation was tested. These mutations caused higher thermostability in Synechocystis sp. PCC6803 so the transformed plant is expected to be the first step in the study of PS II thermostability in higher plants.

The evolution of land plants, particularly the origin of land plants, had long been an issue of concern to biologists. Bryophytes were widely accepted as the first land plants to have emerged during the evolution of land plants (Kenrick 1997, Mishler 1994). But, the phylogeny of the groups within the bryophytes remained debatable. There were currently two popular but conflicting ideas: the liverworts-basal topology (LBT) and the hornworts-basal topology (HBT). This psbA gene study provided additional information to help resolve the debate. Bazzania, Blasia, Megaceros, and Sphagnum psbA gene sequences were generated from this research. The other 24 sequences were obtained from GenBank. The UPGMA, Neighbor-Joining, and Maximum Parsimony trees generated by molecular evolutionary genetic analysis (MEGA) supported the liverworts-basal topology.

Made available in DSpace on 2014-06-11T19:32:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-06Bitstream added on 2014-06-13T19:21:44Z : No. of bitstreams: 1 vieira_vc_dr_jabo.pdf: 991037 bytes, checksum: 6e39ae9e1779bebf699c04fe2aa8cca6 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As plantas daninhas da família Poaceae são as principais plantas que infestam a cultura de cana-de-açúcar. As espécies de gramíneas conhecidas por capim-colchão, estão entre as de maior ocorrência nas lavouras de cana-de-açúcar no Brasil. Atualmente o uso do controle químico está sendo o mais empregado para controle de Digitaria, porém há alguns relatos de falha no controle, principalmente com referência a herbicidas pertencentes ao grupo das triazinas, que bloqueiam a cadeia fotossintética, no fotossistema. As técnicas moleculares estão sendo bem recomendadas para análise da diversidade genética em plantas daninhas. Para a caracterização molecular vinte iniciadores foram utilizados para o RAPO e, para o PCR¬RFLP utilizou-se de dois iniciadores específicos P1 e P2 e a enzima de restrição Mael. O seqüenciamento foi realizado com o amplicom produzido com os iniciadores P1 e P2. Para o tratamento químico utilizou-se a ametrina. Com isso, esse trabalho teve como objetivos: caracterizar dez acessos de Digitaria spp. por marcadores RAPO e PCR¬RFLP, sequenciar uma região conservada do gene psbA e verificar possíveis associações entre o polimorfismo desse gene e a resposta fenotípica à ametrina. Pela análise molecular não houve variabilidade genética entre os acessos e todos apresentaram a mesma resposta fenotípica ao herbicida utilizado. Com esses resultados, concluiu-se que o capim-colchão dos dez acessos estudados pertence à espécie Digitaria nuda e não foi observada relação entre a ocorrência de polimorfismo e a suscetibilidade à ametrina, provavelmente porque todos os acessos estudados foram controlados na dose recomendada do herbicida. / The weed of family Peaceae are the most important infesting sugarcane crop plants. The gramineous species known as crabgrass are among the ones with high occurrence in Brazil sugarcane crop. Presently the use of chemical control is being the most common way used for the control of Digitaria, but with few controlling occurrences fails, with emphasis for those herbicides belonging to triazine group which block the photosynthetic chain at the photosystem II leveI. Molecular techniques are being recommended for the analysis of the genetic diversity such weed. For the molecular characterization twenty primers were used for RAPO and for the PCR¬RFLP a set of two specific primers P1 and P2 were used together with restriction enzyme Mael. The ONA sequencing was performed with an amplicon sample produced with the primers P1 and P2. For the chemical treatment control ametryn was selected. Thus this work had objectives as follows: to characterize ten accessions of Digitaria spp. by RAPO and PCR-RFLP markers, and to sequence a conserved region of the psbA gene so as to investigate the possible polymorphic associations of this gene in response to the phenotypic response to ametryn. For the molecular analysis it did not have genetic variability among the accessions and all had presented the same phenotypic response to the used herbicide. Based on the obtained results, it is concluded the crabgrass that ten collected accessions belong to the species Digitaria nuda, and it was not observed any relation among the polymorphism and susceptibility to ametryn probably because all the studied accessions had been controlled in the recommended dose of the herbicide.

Benthic diatoms are often used as indicators of water quality and past environmental conditions. This depends entirely on a reliable taxonomic system. With the advent of DNA techniques, genetic analyses can now be used in tandem with traditional microscopy in order to improve taxonomy and determine evolutionary relationships. This thesis examined a speciose genus of diatoms Neidium (> 300 species) and, using sequence data from molecular markers as well as traditional morphological analyses, investigated phylogenetic relationships. Fresh benthic samples from aquatic ecosystems in Eastern North America were collected; Neidium taxa were examined using light and scanning electron microscopy then compared to the original specimen types. A total of 124 individual cells were retrieved, amplified, and sequenced for four molecular markers (rbcL, 18S, psbA, and psbC). Phylogenetic reconstructions were completed using Maximum likelihood and Bayesian analyses; when compared with morphological analyses this led to the delineation of several novel Neidium species.

Resumo: As plantas daninhas da família Poaceae são as principais plantas que infestam a cultura de cana-de-açúcar. As espécies de gramíneas conhecidas por capim-colchão, estão entre as de maior ocorrência nas lavouras de cana-de-açúcar no Brasil. Atualmente o uso do controle químico está sendo o mais empregado para controle de Digitaria, porém há alguns relatos de falha no controle, principalmente com referência a herbicidas pertencentes ao grupo das triazinas, que bloqueiam a cadeia fotossintética, no fotossistema. As técnicas moleculares estão sendo bem recomendadas para análise da diversidade genética em plantas daninhas. Para a caracterização molecular vinte iniciadores foram utilizados para o RAPO e, para o PCR¬RFLP utilizou-se de dois iniciadores específicos P1 e P2 e a enzima de restrição Mael. O seqüenciamento foi realizado com o amplicom produzido com os iniciadores P1 e P2. Para o tratamento químico utilizou-se a ametrina. Com isso, esse trabalho teve como objetivos: caracterizar dez acessos de Digitaria spp. por marcadores RAPO e PCR¬RFLP, sequenciar uma região conservada do gene psbA e verificar possíveis associações entre o polimorfismo desse gene e a resposta fenotípica à ametrina. Pela análise molecular não houve variabilidade genética entre os acessos e todos apresentaram a mesma resposta fenotípica ao herbicida utilizado. Com esses resultados, concluiu-se que o capim-colchão dos dez acessos estudados pertence à espécie Digitaria nuda e não foi observada relação entre a ocorrência de polimorfismo e a suscetibilidade à ametrina, provavelmente porque todos os acessos estudados foram controlados na dose recomendada do herbicida. / Abstract: The weed of family Peaceae are the most important infesting sugarcane crop plants. The gramineous species known as crabgrass are among the ones with high occurrence in Brazil sugarcane crop. Presently the use of chemical control is being the most common way used for the control of Digitaria, but with few controlling occurrences fails, with emphasis for those herbicides belonging to triazine group which block the photosynthetic chain at the photosystem II leveI. Molecular techniques are being recommended for the analysis of the genetic diversity such weed. For the molecular characterization twenty primers were used for RAPO and for the PCR¬RFLP a set of two specific primers P1 and P2 were used together with restriction enzyme Mael. The ONA sequencing was performed with an amplicon sample produced with the primers P1 and P2. For the chemical treatment control ametryn was selected. Thus this work had objectives as follows: to characterize ten accessions of Digitaria spp. by RAPO and PCR-RFLP markers, and to sequence a conserved region of the psbA gene so as to investigate the possible polymorphic associations of this gene in response to the phenotypic response to ametryn. For the molecular analysis it did not have genetic variability among the accessions and all had presented the same phenotypic response to the used herbicide. Based on the obtained results, it is concluded the crabgrass that ten collected accessions belong to the species Digitaria nuda, and it was not observed any relation among the polymorphism and susceptibility to ametryn probably because all the studied accessions had been controlled in the recommended dose of the herbicide. / Orientador: Janete Apparecida Desidério Sena / Coorientador: Pedro Luís da Costa Aguiar Alves / Banca: Robinson Antonio Pitelli / Banca: Josélia Oliveira Marques / Banca: Nubia Maria Correia / Banca: José Eduardo Garcia / Doutor

Variability in the genetic information DNA tracking individuals carry is easy to detect using molecular markers. In the thesis we examined related Dracaena species. For the study of genetic diversity in the genus Dracaena are used mainly noncoding regions of cpDNA, spacer trnH -- psbA, regions trnL -- trnF and trnS -- trnG -- trnG, which are more variable than coding regions. Also used in this work were coding regions of matK and rbcL. In the genus Dracaena belongs xerophytic species that are characterized by typical shaped treetop. 14 representatives of species were used in thesis growing in tropical regions of the African continent and adjacent islands and the southeastern part of the Arabian peninsula. They are monocotyledonous trees with atypical abilities of secondary thickness of trunk, which I find interesting. The massive trunk is very strong and there is potencial to used it for wood. Trees are very significant for their red plant sap which flowing from demaged trunk. The sap is very precious resource which is used in many areas of industry, for example pharmacy, traditional medicine, dye making etc. Determination of genetic affinity was based on an amplification of cpDNA template of individual Dracaena samples with primers for the studied regions. Data was obtained and evaluated by Multiple alignment program ClustalX and BioEdit after their sequencing. Evalueted data was used to create dendograms affinity. According the resulting phylogenetic tree we find out similarities and identified relationship of the monitored species of the genus Dracaena. The main purpose of research was to get answers to understand phylogenetic relationship between group of Dracaena forestry used trees. The thesis was made in cooperation of Department of Forest Botany, Dendrology and Geobiocoenology, Faculty of Forestry and Wood Technology of Mendel University in Brno.

As técnicas de DNA barcoding (código de barras de DNA) têm como objetivo principal a identificação taxonômica de organismos através da amplificação e análise de sequências de DNA curtas, padronizadas e previamente definidas. Apesar do sucesso relativo desta abordagem em animais usando um único locus, a aplicação deste método em plantas apresenta menor capacidade de identificar espécies usando uma única região gênica, levando a necessidade de utilização de múltiplos loci. Além disso, ainda há certo debate sobre qual região gênica seria mais apropriada para o DNA barcoding em plantas, embora as regiões plastidiais rbcL, matK e o espaçador intergênico trnH-psbA juntamente com o espaçador intergênico nuclear do RNA ribossomal (ITS) sejam as mais comumente utilizadas até então. As tribos Sisyrinchieae e Tigridieae da família Iridaceae foram testadas de acordo com diferentes métodos e marcadores indicados para o DNA barcoding em plantas. Os resultados indicaram uma alta universalidade para membros da tribo Sisyrinchieae, mas também revelaram uma capacidade de identificação de espécies considerada baixa. Apesar disto, os espaçadores ITS foram indicados como a melhor sequência para DNA barcoding em Sisyrinchieae. Em Tigridieae, problemas inerentes ao sequenciamento impediram a utilização dos ITS em nossas análises. Assim, apenas marcadores plastidiais foram utilizados na tentativa de identificar espécies, apresentando novamente resultados modestos. A região gênica que atingiu maior capacidade de identificação em Tigridieae foi o gene matK. A incapacidade de se alcançar maiores taxas de identificação provavelmente está relacionada à complexa história evolutiva apresentada pelos grupos em análise. Este trabalho forneceu o primeiro conjunto significativo de dados de DNA barcoding aplicados a dois importantes grupos de Iridaceae de considerável biodiversidade no Brasil. As tribos em análise apresentam espécies consideradas filogeneticamente próximas e são de difícil identificação devido a sua morfologia homogênea, principalmente em estado vegetativo, justificando plenamente o uso de métodos molecularespara a identificação taxonômica. / The main objective of DNA barcoding methods is the taxonomic identification of organisms by amplifying and analyzing short, standardized and previously defined DNA sequences. In spite of the relative success of this approach in animals using a single locus, the application of this method in plants has less ability to identify species using a single gene region, leading to the need of using multiple loci. Furthermore, there is still some debate concerning which gene region would be more suitable for DNA barcoding in plants, although the plastid regions rbcL, matK and the trnH-psbA intergenic spacer along with the nuclear intergenic spacer of ribossomal DNA (ITS) are the most commonly regions used thus far. The tribes Sisyrinchieae and Tigridieae of the family Iridaceae were tested according to different methods and markers used for DNA barcoding in plants. The results indicated a great universality for members of tribe Sisyrinchieae, but also showed a low ability to identify species. Nevertheless, ITS was imputed as the best sequence for DNA barcoding in Sisyrinchieae. In Tigridieae, problems inherent of ITS sequencing prevented its use in our analysis. Thus, only plastid markers were used in an attempt to identify species, showing modest results once again. The gene region that reached higher identification ability in Tigridieae was matK. The inability to achieve higher identification levels is probably related to the complex evolutionary history presented by the groups in question. This work provided the first large data set of DNA barcoding applied to two important groups of Iridaceae with significant biodiversity in Brazil. The tribes in question present species considered phylogenetically related and are difficult to identify due to their homogeneous morphology, especially in vegetative stage, fully justifying the use of molecular methods for taxonomic identification.

As técnicas de DNA barcoding (código de barras de DNA) têm como objetivo principal a identificação taxonômica de organismos através da amplificação e análise de sequências de DNA curtas, padronizadas e previamente definidas. Apesar do sucesso relativo desta abordagem em animais usando um único locus, a aplicação deste método em plantas apresenta menor capacidade de identificar espécies usando uma única região gênica, levando a necessidade de utilização de múltiplos loci. Além disso, ainda há certo debate sobre qual região gênica seria mais apropriada para o DNA barcoding em plantas, embora as regiões plastidiais rbcL, matK e o espaçador intergênico trnH-psbA juntamente com o espaçador intergênico nuclear do RNA ribossomal (ITS) sejam as mais comumente utilizadas até então. As tribos Sisyrinchieae e Tigridieae da família Iridaceae foram testadas de acordo com diferentes métodos e marcadores indicados para o DNA barcoding em plantas. Os resultados indicaram uma alta universalidade para membros da tribo Sisyrinchieae, mas também revelaram uma capacidade de identificação de espécies considerada baixa. Apesar disto, os espaçadores ITS foram indicados como a melhor sequência para DNA barcoding em Sisyrinchieae. Em Tigridieae, problemas inerentes ao sequenciamento impediram a utilização dos ITS em nossas análises. Assim, apenas marcadores plastidiais foram utilizados na tentativa de identificar espécies, apresentando novamente resultados modestos. A região gênica que atingiu maior capacidade de identificação em Tigridieae foi o gene matK. A incapacidade de se alcançar maiores taxas de identificação provavelmente está relacionada à complexa história evolutiva apresentada pelos grupos em análise. Este trabalho forneceu o primeiro conjunto significativo de dados de DNA barcoding aplicados a dois importantes grupos de Iridaceae de considerável biodiversidade no Brasil. As tribos em análise apresentam espécies consideradas filogeneticamente próximas e são de difícil identificação devido a sua morfologia homogênea, principalmente em estado vegetativo, justificando plenamente o uso de métodos molecularespara a identificação taxonômica. / The main objective of DNA barcoding methods is the taxonomic identification of organisms by amplifying and analyzing short, standardized and previously defined DNA sequences. In spite of the relative success of this approach in animals using a single locus, the application of this method in plants has less ability to identify species using a single gene region, leading to the need of using multiple loci. Furthermore, there is still some debate concerning which gene region would be more suitable for DNA barcoding in plants, although the plastid regions rbcL, matK and the trnH-psbA intergenic spacer along with the nuclear intergenic spacer of ribossomal DNA (ITS) are the most commonly regions used thus far. The tribes Sisyrinchieae and Tigridieae of the family Iridaceae were tested according to different methods and markers used for DNA barcoding in plants. The results indicated a great universality for members of tribe Sisyrinchieae, but also showed a low ability to identify species. Nevertheless, ITS was imputed as the best sequence for DNA barcoding in Sisyrinchieae. In Tigridieae, problems inherent of ITS sequencing prevented its use in our analysis. Thus, only plastid markers were used in an attempt to identify species, showing modest results once again. The gene region that reached higher identification ability in Tigridieae was matK. The inability to achieve higher identification levels is probably related to the complex evolutionary history presented by the groups in question. This work provided the first large data set of DNA barcoding applied to two important groups of Iridaceae with significant biodiversity in Brazil. The tribes in question present species considered phylogenetically related and are difficult to identify due to their homogeneous morphology, especially in vegetative stage, fully justifying the use of molecular methods for taxonomic identification.

As técnicas de DNA barcoding (código de barras de DNA) têm como objetivo principal a identificação taxonômica de organismos através da amplificação e análise de sequências de DNA curtas, padronizadas e previamente definidas. Apesar do sucesso relativo desta abordagem em animais usando um único locus, a aplicação deste método em plantas apresenta menor capacidade de identificar espécies usando uma única região gênica, levando a necessidade de utilização de múltiplos loci. Além disso, ainda há certo debate sobre qual região gênica seria mais apropriada para o DNA barcoding em plantas, embora as regiões plastidiais rbcL, matK e o espaçador intergênico trnH-psbA juntamente com o espaçador intergênico nuclear do RNA ribossomal (ITS) sejam as mais comumente utilizadas até então. As tribos Sisyrinchieae e Tigridieae da família Iridaceae foram testadas de acordo com diferentes métodos e marcadores indicados para o DNA barcoding em plantas. Os resultados indicaram uma alta universalidade para membros da tribo Sisyrinchieae, mas também revelaram uma capacidade de identificação de espécies considerada baixa. Apesar disto, os espaçadores ITS foram indicados como a melhor sequência para DNA barcoding em Sisyrinchieae. Em Tigridieae, problemas inerentes ao sequenciamento impediram a utilização dos ITS em nossas análises. Assim, apenas marcadores plastidiais foram utilizados na tentativa de identificar espécies, apresentando novamente resultados modestos. A região gênica que atingiu maior capacidade de identificação em Tigridieae foi o gene matK. A incapacidade de se alcançar maiores taxas de identificação provavelmente está relacionada à complexa história evolutiva apresentada pelos grupos em análise. Este trabalho forneceu o primeiro conjunto significativo de dados de DNA barcoding aplicados a dois importantes grupos de Iridaceae de considerável biodiversidade no Brasil. As tribos em análise apresentam espécies consideradas filogeneticamente próximas e são de difícil identificação devido a sua morfologia homogênea, principalmente em estado vegetativo, justificando plenamente o uso de métodos molecularespara a identificação taxonômica. / The main objective of DNA barcoding methods is the taxonomic identification of organisms by amplifying and analyzing short, standardized and previously defined DNA sequences. In spite of the relative success of this approach in animals using a single locus, the application of this method in plants has less ability to identify species using a single gene region, leading to the need of using multiple loci. Furthermore, there is still some debate concerning which gene region would be more suitable for DNA barcoding in plants, although the plastid regions rbcL, matK and the trnH-psbA intergenic spacer along with the nuclear intergenic spacer of ribossomal DNA (ITS) are the most commonly regions used thus far. The tribes Sisyrinchieae and Tigridieae of the family Iridaceae were tested according to different methods and markers used for DNA barcoding in plants. The results indicated a great universality for members of tribe Sisyrinchieae, but also showed a low ability to identify species. Nevertheless, ITS was imputed as the best sequence for DNA barcoding in Sisyrinchieae. In Tigridieae, problems inherent of ITS sequencing prevented its use in our analysis. Thus, only plastid markers were used in an attempt to identify species, showing modest results once again. The gene region that reached higher identification ability in Tigridieae was matK. The inability to achieve higher identification levels is probably related to the complex evolutionary history presented by the groups in question. This work provided the first large data set of DNA barcoding applied to two important groups of Iridaceae with significant biodiversity in Brazil. The tribes in question present species considered phylogenetically related and are difficult to identify due to their homogeneous morphology, especially in vegetative stage, fully justifying the use of molecular methods for taxonomic identification.

La photosynthèse permet de convertir l’énergie solaire en énergie chimique. Ce processus met en jeu un grand nombre de protéines et complexes protéiques. Le premier complexe de la chaîne photosynthétique est le photosystème II où a lieu l’oxydation de l’eau. Le PSII est composé des protéines D1 et D2. Chez la cyanobactérie thermophile Thermosynechococcus elongatus, il y a trois gènes qui codent trois protéines D1 différentes. La première partie de la thèse décrit le développement d’outils protéomiques basés sur les gels d’électrophorèse 2D pour étudier le protéome des trois différents variants, qui expriment chacun une seule protéine pour D1. Peu de différences ont été trouvées. Toutefois, un seul des variants exprime Tll0287. La deuxième partie de la thèse décrit la caractérisation de Tll0287 avec différents techniques : spectroscopies d’absorption UV-visible ou de résonance Raman et spectro-électrochimie. Tll0287 a été identifié comme un cytochrome de type c, mais il présente beaucoup de caractéristiques inattendues. Les spectres d’absorption UV-visible et de résonance Raman de Tll0287 réduit montrent une dépendance vis-à-vis du pH. Deux formes d’hèmes sont présents dans chacun des états oxydé et réduit. Un changement du ligand cystéine a été observé quand l’hème est réduit. Les titrages redox présentent de multiples potentiels à pH 10 et pH 5. Tll0287 peut fixer une molécule de CO à pH 7,6. Ces caractéristiques suggèrent que Tll0287 pourrait être une protéine senseur. De plus, la structure cristallographique montre que Tll0287 n’a pas un repliement classique d’un cytochrome de type c mais celui d’une protéine senseur. Les mutants de délétion du gène tll0287 ont été construits et aideront à comprendre la fonction de ce nouveau cytochrome. La troisième partie décrit l’étude de PsbV2 : un autre cytochrome de type c. Afin d’obtenir en quantité suffisante la protéine pour permettre sa caractérisation, elle a été surexprimée dans un système homologue en utilisant le promoteur de l’enzyme de la rubisco. Le potentiel redox de PsbV2 a été déterminé, comme étant très bas, inférieur à -460 mV (vs SHE, pH 5). Le spectre d’absorption UV-visible de la forme réduite a été caractérisé. La structure cristallographique de PsbV2 a été résolue et a révélé une cystéine comme ligand axial et un repliement proche de celui de cytochromes connus de T.elongatus. Bien que Tll0287 et PsbV2 présentent une cystéine comme ligand axial, leurs structures et leurs propriétés physico-chimiques suggèrent que leurs fonctions sont bien différentes. Une contribution majeure de cette thèse est la caractérisation d’un nouveau senseur à hème de type c chez les cyanobactéries et le développement d’outils nécessaires pour son étude. / Photosynthesis converts solar energy into chemical energy. This process involves a large number of proteins and protein complexes. The first protein complex in the photosynthetic chain is Photosystem II within the oxidation of water takes place. PSII is composed of the D1 and D2 proteins. In the thermophile cyanobacterium Thermosynechococcus elongatus, three genes encoded three different D1 proteins. The first part of this thesis describes the development of proteomics tools based on 2D gel-electrophoresis to study the proteome of three different variants, each expressing a single different D1 protein. Very few differences were found. However, only one expressed the protein Tll0287. The second part of the thesis describes the characterization of Tll0287. It was characterized using different techniques: electronic absorption and Raman resonance spectroscopies and spectro-electrochemistry. Tll0287 has been previously identified as a c-type cytochrome, but it presents some unexpected characteristics. The UV-visible absorption and Raman resonance spectra of reduced Tll0287 show a pH dependence. The reduced and oxidized states each had two different forms of the heme. A switch of ligands from a cysteine to histidine was observed in the reduced state. Redox titration showed multiple midpoints at pH 10 and 5. Tll0287 was shown to fix a CO molecule at pH 7.6. These physical properties suggested that Tll0287 could be a sensor. The crystallographic studies reveal that Tll0287 does not have a classical c-type cytochrome fold and is similar to other known sensor proteins, strengthening the hypothesis that it is a sensor. Deletion mutants were constructed that will help to better understand the function of this new cytochrome. The third part describes a study of the PsbV2, another c-type cytochrome. In order to obtain sufficient quantities to carry out characterization of this protein, it was overexpressed in a homologous system using the promotor of the rubisco enzyme. The redox midpoint potential of PsbV2 was found to be very low, below -460 mV (vs SHE, pH 5). The UV-visible absorption spectrum of the reduced form was determined. The crystallographic structure of PsbV2 was solved and reveals an axial cysteine ligand. Although both Tll0287 and PsbV2 share this feature, their different structures and physico-chemical properties suggest that their functions are unlikely to be similar. A major contribution of this thesis is the characterization of a new c-type cytochrome sensor in cyanobacteria and the development of proteomic tools required to study it.