Dans le domaine des plantes, la formation de la fleur a été un pas crucial dans la capacité des végétaux à coloniser une grande diversité de niches écologiques sur notre planète. Les deux espèces Petunia x hybrida et Arabidopsis thaliana représentent deux groupes majeurs des plantes à fleur. Nous avons montré que les gènes à homéodomaine d’une famille appelée WOX (Wuschel homeobOX) sont fortement impliqués dans le développement des organes dotés de polarité (dont les feuilles et des organes de la fleur : sépales, pétales, carpelles). Un double mutant (maw mawb), chez le Pétunia, développe des pétales en forme de filament, avec disparition du tube floral. De plus, nous avons découvert que ces mêmes gènes interagissent au niveau génétique avec d’autres gènes (appelés gènes à boite MADS) dans la formation des ovules, structures à partir desquelles les graines se forment. Nous avons aussi montré que des gènes de la même famille sont impliqués dans la formation d’autres structures chez le Pétunia : les trichomes ou poils aériens de surface. Ces derniers sont impliqués dans plusieurs taches, qui vont de la protection contre les pathogènes à celles contre les stress abiotiques. Grâce à des études de génétique fonctionnelle nous avons pu montrer un recrutement différentiel des gènes WOX ici étudiés, dépendant de l’organe et de l’espèce. Ces travaux de thèse montrent l’importance de cette famille génique pour les études d’evo-devo (Biologie Evolutionniste du Développement). Finalement, une analyse de RNA-Seq (séquençage du transcriptome), dévoile les réseaux génétiques contrôlés par ces gènes WOX. / In the Kingdom of Plants, the emergence of flowers was a crucial step in their ability to colonize a large variety of ecological niches on our planet. The two species Petunia x hybrida and Arabidopsis thaliana represent two major groups of flowering plants. In this work, we have shown that HOMEOBOX genes from the WOX family (Wuschel homeoboxes) are heavily involved in polar organ development (such as leaves and sepals, petals, and carpels at the flower level). The maw mawb double mutant in Petunia displays string-like petals, with consequent disappearance of the floral tube. Moreover, we found that these two genes genetically interact with genes from a different family (the MADS family) in ovule identity (ovules are the structures from which seeds develop). We have also shown that other genes from the WOX family are involved in development of a different kind of structures in Petunia: the trichomes. Trichomes are involved in different tasks, protecting the plant from pathogens or abiotic stress. Thanks to functional genetics studies, we have shown functional genetic recruitment of these WOX genes among different plant organs and among different species. This PhD thesis provides evidence for the importance of the WOX family in Evo-Devo studies. Eventually, we unravelled genetic networks controlled by MAW and MAWB trough RNA-Seq analysis.

In recent years, the conventional Flash memory with floating structure is expected to reach physical limits as devices scaling down in near future. In order to overcome this problem, alternative memory technologies have been widely investigated. And the resistance random access memory (RRAM) has attracted extensive attention for the application in next generation nonvolatile memory, due to the excellent memory property including lower consumption of energy, lower operating voltage, higher density, fast operating speed, simple structure, higher endurance, retention and process compatibility with CMOS. In this study, the tungsten-based oxide is chosen as RRAM switching layer because the tungsten is compatible with the present complementary metal oxide semiconductor (CMOS) process. The Pt/WOX/TiN structure device cells had the resistance switching property successfully. However, the experiment result revealed the inferior resistance switching property. The resistance switching characteristic of the WOX thin film is extremely unstable, it is impossible to become the products. Compared with WOX, the resistance switching property of WSiOX RRAM device is improved substantially such as stability of resistance states and reliability of device. In second parts, we purposed two methods to enhance the device switching characteristic, including controlling the filament formation/ interruption in the W doped SiOX layer and restricting oxygen movement in the WSiON layer. Finally, the transport mechanisms of carrier is analyzed and researched from the current-voltage (I-V) switching characteristic of the device. A designed circuit was used in this study to accurately observe the resistance switching process with a pulse generator and oscilloscope, which reveals that the switching process is related to both time and voltage. The oxygen movement will drift in the low temperature due to the electrical field and restricted the crystal lattice vibration. But, it will diffuse through thermal dynamics in the high temperature.

This thesis deals with one-dimensional (1D) and two-dimensional nanomaterials (2D) in terms of their utilization for new types of gas sensors. Thesis focuses on study of sensing elements for gas sensors based on semiconductor metal oxide materials (MOX) and their manufacturing technology. The objective of the thesis is the design and implementation of a sensing elements formed by selected nanomaterials based on the structure of interdigital electrodes. The result of the practical part of the thesis is the characterization and comparison of materials in terms of their detection parameters in the presence of selected test gases. The first part of thesis hierarchically defines chemoresistive gas sensor, characterizes and explains its operation principle. Second part studies 1D and 2D nanomaterials of sensing elements for MOX chemoresistive gas sensors, contains a research of their properties and describes their methods of manufacturing and implementation. The last part deals with the implementation of the sensitive layer of the sensor with selected nanomaterials, characterizes and compares their detection properties.

The project goals for this dissertation were to manipulate Populus trichocarpa source-sink relationships to optimize this woody crop species for specific agricultural traits such as increased growth rate, stress tolerance and/or improvements in overall biomass accumulation. We targeted specific tissues such as xylem, where alterations in the relationship of source and sink tissues can lead to the control of xylem cell deposition or of various wood properties. This led to the characterization of 165 protein-protein interactions and 20 protein-DNA interaction which constitute numerous woody tissue related subnetworks. One such network, centered on the DIVARACATA and RADIALIS INTERACTING FACTOR (PtrDRIF), identified PtrWOX13c as an interacting protein. Characterization of PtrWOX13c shows that it displays the ability to control promoters related to lignin biosynthesis genes and overexpression phenotypes show alterations in axillary branch activity. Genes which control the differentiation and specialization of cells such as members of the WOX family are also highly responsive to abiotic stress which can force major changes in plant metabolism and nutrient mobilization. ABA, a prominent plant phytohormone with known roles in the adaptation to stress has shown novel connections in the regulation of growth promoting complexes such as TOR through antagonistic regulatory actions of the SnRK2 protein kinase in Arabidopsis. Characterization of the core ABA signaling in P. trichocarpa has identified a regulatory clade A protein phosphatase which interacts with numerous PtrSnRK2 proteins and when overexpressed in hybrid poplar results in increased height and node production potentially by indirect control of growth promoting complexes like TOR through SnRK2 inhibition. This work has also demonstrated that in addition to the involvement of phytohormones in the regulation of plant development, sugar phosphates such as T6P can exert significant control of plant architecture. Together, these studies comprise the discovery and subsequent characterization of novel wood associated networks, hormone pathways and sugar signaling in the manipulation of P. trichocarpa source-sink relationships for the promotion of biomass accumulation. / PHD / Detailed analyses of gene activity in different tissues or under the influence of various environmental conditions have identified numerous genes that control desirable traits and plant characteristics. However, the activities and functions of the proteins produced from these genes is less understood. One of the ways proteins work is through the formation of complexes with other proteins. Using the commercially valuable tree Populus trichocarpa (poplar) as our research model, we have identified novel complexes of interacting proteins with the potential to sense and respond to the environment and to promote plant growth. We tested the function of some of the members of these newly discovered protein complexes using transgenic poplar. As a result, we revealed previously unknown functions for two poplar proteins: PtrWOX13c promoted increased branching and PtrHAB2 promoted an increase in tree height. Independent of these functional analyses of poplar proteins, we also tested the ability of a sugar phosphate, trehalose6-phosphate, known from previous work to regulate plant growth, for its ability to promote poplar growth. We found that reducing levels of trehalose-6-phosphate resulted in increased branch growth, similar to the impact of the PtrWOX13c protein. In summary, identification of new protein complexes is a valuable strategy for the discovery of proteins that can increase tree growth. Additionally, combining targeted changes in both proteins and regulatory sugars may be a promising path toward future crop improvement and tree domestication.