The greening of etiolated first leaf blades of wheat (Triticium aestivum Mercia) seedlings (referred to in the text as leaf tissue) was studied in relation to tissue age and water stress. Use was made of whole seedlings, excised leaf blades and leaf blade segments. Responses to photoperiodic illumination were measured as changes in the levels of chlorophyll, total soluble protein and nucleic acids (both total and specific fractions). The pattern of greening in the whole seedlings, excised leaf blades and leaf blade segments was essentially the same in 6 and 10 day-old dark-grown tissues, where chlorophyll accumulation followed the age sequence along the leaf. Least chlorophyll accumulated in the tip of leaves of both ages but the older leaves contained less overall pigment than the younger leaves. Patterns of total soluble protein and total nucleic acid accumulation did not reflect the pattern shown by the chlorophyll. Protein accumulated most in the tip region, with nucleic acids being highest in the middle region. Water stress treatment reduced chlorophyll accumulation in leaf blade tissue, particularly in the intact seedlings. Protein levels, however, were more variable and appeared to reflect the ability of the younger tissue to accumulate this compound as a stress metabolite. Total nucleic acid levels were also elevated under water stress. Again, these effects were most marked on the intact seedlings, implying that an effect on the roots was also involved. The data from polyacrylamide gel electrophoresis of RNA fractions showed that the level of chloroplast RNA components was maintained up to 17 days for tissue incubated in the dark as well as in the light. Severe water stress treatments applied to the roots of whole seedlings resulted in the loss of ribosomal fraction in the leaves. However, this effect was not seen with mild water stress. Kinetin treatments during water stress did not appear to alter the pattern of cell component accumulation although in unstressed material, treatment with this compound enhanced chlorophyll accumulation slightly, especially in the young tissue. This indicates that, at the concentration used, the growth regulator was not able to alleviate the stress condition. The leaf blades of intact seedlings responded in a specific way which was much more pronounced than for excised leaf blades or leaf blade segments. It was concluded that some signalling was involved between the root and shoot tissues during water stress treatments.

Mechanically isolated cell cultures were chosen as a model system to examine wound-induced dedifferentiation at the molecular level as large quantities of physiologically and morphologically similar G1-arrested mesophyll cells could be obtained. Within 5 days of culture such non-dividing, photosynthetic cells become heterotrophic, and have completed a first nuclear division and cytokinesis. There are few changes in cell morphology during the first 2-3 days in culture. However, during this period there is a massive increase in respiration rate and total RNA synthesis. Following DNA synthesis there is a rapid cell expansion, mitosis and cytokinesis. Steady state transcript populations were monitored through the first 8 days of culture by analysis of the products of in vitro translations on 2-D gels. Large changes in gene expression were evident during the first 3 days in culture with several genes highly up-regulated and others down-regulated. Dedifferentiation can be separated into 3 different phases. Firstly, reactivation of the cell cycle during which there are few cytological or physiological changes but gross changes in the expression of genes possibly associated with wounding or stress. Secondly, DNA synthesis, first mitosis event and phragmoplast formation during which there are minor changes in transcript abundance. Finally a continuation of the cell cycle with little alteration in transcript abundance. Changes in plastid morphology are only apparent after 10-14 days resulting in the formation of proplastid like structures. However, mRNA for both large subunit ribulose bisphosphate carboxylase and small subunit ribulose bisphosphate carboxylase decrease to basal levels within a day of culture and photosynthetic capacity diminishes when the first cell division is evident. Plastid dedifferentiation can therefore be considered separately and proceeds slowly being more or less complete after 2-3 cell divisions. Dedifferentiation is therefore seen to be a complex process which involves the interaction of several factors i.e wounding and hormones and results in temporal changes in transcript abundance, changes in the mode of respiration, morphology and cell proliferation.

There are a vast number of transcription factors that regulate plant growth and development. The NAC gene superfamily is one of the largest families of transcription factors in the plant kingdom. NAC gene expression profiles using Affymetrix ATH1 gene chips were obtained for different plant organs: heart embryo, mature embryo, leaf, root and flower. NAC gene expression profiles proved to be very complex, except for one NAC gene detected only in floral tissue, At1g61110. At1g61110 was shown to be specifically expressed in the anther tapetum of Arabidospis; therefore, its name was changed to TAPNAC. TAPNAC became the focus of our studies. We identified a tapnac T-DNA knockout (KO) line, SALK_069450. A molecular phenotype was observed. Several oligopeptide, sugar and metal transporters were differentially expressed. Coincidentally, a wheat NAC gene, named TaNAM-B1 for its high sequence similarity to ATNAM, TAPNAC and At3g15510 was found to be involved in nutrient remobilization. PHOSPHOLIPASE Dα1 (PLDα1) was also found to be down-regulated in the tapnac KO. PLDα1 is an enzyme which hydrolyzes phospholipids that are part of tapetal cell membranes and tapetal lipid bodies. Once these tapetal cell structures are disrupted, the secretion of the compounds that form part of the pollen coat (i.e. proteins, flavonoids and lipids) into the anther locule is facilitated. Promoter deletion analysis using a GUS reporter and later GUS immuno-localization confirmed the findings of Wellmer and others. TAPNAC is a tapetal specific gene. The cis-regulatory sequence that enhances tapetal expression in the TAPNAC promoter was identified. The consensus motif TCGTGT increased tapetal expression of a GUS reporter gene, only when flanked by the TAPNAC minimal promoter region (-217 bp to +51 bp). In summary, TAPNAC transcription factor has been characterized and data indicates that it could play a role in nutrient remobilization from the tapetum to the pollen grains, particularly during late floral stages. Also, important information on tapetal specifcation cis-regulatory sequences was discovered. The consensus motif TCGTGT, present in TAPNAC promoter, was shown to enhance tapetal expression of a GUS reporter gene.

There are a vast number of transcription factors that regulate plant growth and development. The NAC gene superfamily is one of the largest families of transcription factors in the plant kingdom. NAC gene expression profiles using Affymetrix ATH1 gene chips were obtained for different plant organs: heart embryo, mature embryo, leaf, root and flower. NAC gene expression profiles proved to be very complex, except for one NAC gene detected only in floral tissue, At1g61110. At1g61110 was shown to be specifically expressed in the anther tapetum of Arabidospis; therefore, its name was changed to TAPNAC. TAPNAC became the focus of our studies. We identified a tapnac T-DNA knockout (KO) line, SALK_069450. A molecular phenotype was observed. Several oligopeptide, sugar and metal transporters were differentially expressed. Coincidentally, a wheat NAC gene, named TaNAM-B1 for its high sequence similarity to ATNAM, TAPNAC and At3g15510 was found to be involved in nutrient remobilization. PHOSPHOLIPASE Dα1 (PLDα1) was also found to be down-regulated in the tapnac KO. PLDα1 is an enzyme which hydrolyzes phospholipids that are part of tapetal cell membranes and tapetal lipid bodies. Once these tapetal cell structures are disrupted, the secretion of the compounds that form part of the pollen coat (i.e. proteins, flavonoids and lipids) into the anther locule is facilitated. Promoter deletion analysis using a GUS reporter and later GUS immuno-localization confirmed the findings of Wellmer and others. TAPNAC is a tapetal specific gene. The cis-regulatory sequence that enhances tapetal expression in the TAPNAC promoter was identified. The consensus motif TCGTGT increased tapetal expression of a GUS reporter gene, only when flanked by the TAPNAC minimal promoter region (-217 bp to +51 bp). In summary, TAPNAC transcription factor has been characterized and data indicates that it could play a role in nutrient remobilization from the tapetum to the pollen grains, particularly during late floral stages. Also, important information on tapetal specifcation cis-regulatory sequences was discovered. The consensus motif TCGTGT, present in TAPNAC promoter, was shown to enhance tapetal expression of a GUS reporter gene.

No description available.

Les annexines sont définies comme étant des protéines qui se lient de manière calcium-dépendante aux phospholipides membranaires chargés négativement. Elles ont été associées à différents processus biologiques tels les réponses des plantes aux stress biotiques et abiotiques. Nous avons identifié une annexine végétale, appelée Ntann12, dont l’expression est induite après infection des plantes par la bactérie Rhodococcus fascians. Ntann12 possède les domaines caractéristiques des annexines et se lie aux phospholipides chargés négativement, de manière calcium-dépendante. L’expression de Ntann12 est très abondante dans les cellules différentiées des racines, où la protéine a été détectée par immunolocalisation dans le cytosol et dans le noyau. Des analyses par western blot ont montré que l’accroissement relatif de la quantité de protéines liées aux membranes est positivement corrélé à l’augmentation de la concentration en Ca2+. Au niveau physiologique, l'expression de Ntann12 est induite par l’apport exogène d’auxine. Elle est contrôlée dans les racines par un signal induit par la lumière, et provenant des parties aériennes. Le transport polaire de l'auxine a été identifié comme étant le processus cellulaires nécessaires à l'expression de Ntann12 dans les racines. En outre, cette expression est réprimée par les stress salin, osmotique et hydrique. Ces résultats suggèrent que l’annexine Ntann12 est impliquée dans le métabolisme de l’auxine. / Annexins are defined as calcium-binding proteins, and they have been associated in plants with different biological processes such as responses to biotic and abiotic stress. Ntann12 expression is induced upon infection of tobacco plant by R. fascians. Ntann12 possesses the conserved annexin repeat with the sequence for type II Ca2+-binding site and recombinant as well as native Ntann12 binds to negatively charged phospholipids in a Ca2+-dependent manner. It is mainly expressed in root differentiated cells where the protein was immunolocalized in the cytosol and in the nucleus. Ntann12 was examined by western blot in both microsomal and cytosolic fractions from tobacco roots cells, and was detected in both the cytosol and microsome. The relative increase of Ntann12 proteins associated with the microsome is coupled with an increase in Ca2+ concentration. At the physiological level, Ntann12 expression is induced by exogenous application of auxin, and was found to be regulated in the root system by a light-induced signal coming from plant aerial part and polar auxin transport was identified to be the cellular process required for Ntann12 expression in root cells. Furthermore, Ntann12 expression is down-regulated by salt, osmotic and water stress. These results collectively suggest that the annexin Ntann12 is implicated in auxin metabolism.

Receptor-like kinases (RLKs) are encoded for by one of the largest gene families in Arabidopsis and represent the predominant form of cell surface receptors in plants. RLKs mediate signal transduction in diverse processes including steroid-mediated growth pathways, pathogen-triggered innate immune responses. Here I present characterization of mutant phenotypes, expression patterns, and genetic interactions for the BAK1 INTERACTING RECEPTOR (BIR) family of Leucine-rich Repeat-RLKs, three members of which have had no previous characterization. Furthermore, I show that cell death, aerial growth, and lateral root development defects in bir1-1 are suppressed by mutations of the LRR-RLK co-receptor BRI1-ASSOCIATED KINASE 1 (BAK1); I identify a novel primary root growth phenotype in bir1-1 mutants, as well as a lateral root development phenotype for bir3 mutants; and primary root growth and aerial defects in bir3.bir4;bak1 triple mutants. Using an allelic series of bak1 mutations I show that bir phenotypes are dependent upon particular functions of BAK1, and propose that the BIR family exhibits a novel function, previously undescribed for LRR-RLKs, as regulators of co-receptor/ligand-binding receptor complex specificity.

Made available in DSpace on 2014-06-11T19:32:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-20Bitstream added on 2014-06-13T20:03:19Z : No. of bitstreams: 1 defazio_jl_dr_botib.pdf: 529161 bytes, checksum: 8529229e3ef9ec911a0b6e5f4d1a491e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Embora o cálcio tenha sido extensivamente estudado, o metabolismo deste macronutriente precisa ser melhor avaliado, uma vez que este elemento atua como mensageiro secundário nas vias de transdução de sinal em células vegetais e, devido às variações em sua concentração celular, atua por meio de proteínas moduladoras e suas moléculas-alvo, regulando vários processos celulares, incluindo desde o controle do transporte iônico até a expressão gênica. Neste contexto, existem dúvidas sobre o efeito do cálcio no desenvolvimento das plantas, nas trocas gasosas e na rota de produção dos óleos essenciais, especialmente no rendimento e composição química. Este estudo objetivou ampliar o conhecimento sobre aspectos do metabolismo do cálcio em Mentha piperita, uma espécie medicinal e aromática, quando cultivada em solução nutritiva. Avaliou-se a influência da variação dos níveis de cálcio nos índices fisiológicos, nas trocas gasosas e no rendimento e composição química do óleo essencial. Para tanto, as plantas foram cultivadas durante seu desenvolvimento em solução nutritiva no 2 de Hoagland & Arnon contendo 160 mg L-1 de cálcio e modificada para fornecimento de 200, 120, 80 e 40 mg L-1. Aos 45, 65, 85, 105 e 140 dias após o transplante (DAT) das mudas para a solução de cultivo, foram avaliados os índices fisiológicos área foliar, matéria seca de lâminas foliares e total, além do rendimento e da composição química do óleo essencial. Para análise das variáveis das trocas gasosas foi utilizado sistema aberto portátil de fotossíntese (LI-6400, Li-Cor Inc., NE, USA), determinando-se, aos 65, 85 e 105 DAT, a assimilação de CO2, transpiração, condutância estomática, concentração intercelular de CO2 e eficiência do uso... / Although calcium has been extensively studied, the metabolism of this macronutrient needs further evaluation since this element acts as a secondary messenger in signal transduction pathways in plant cells and, due to variations in its cell level, acts by means of modulator proteins and their target molecules, regulating several cell processes, from ion transportation control to gene expression. Thus, there are doubts about the effect of calcium on plant development, gas exchanges and essential oil production route, especially concerning yield and chemical composition. This study aimed to expand the knowledge of calcium metabolism aspects in Mentha piperita, an aromatic medicinal species, grown under nutrient solution. The influence of calcium level variation on physiological indexes, gas exchanges and essential oil yield and chemical composition was assessed. The plants were grown during their development in Hoagland & Arnon nutrient solution number 2 containing 160 mg L-1 and modified to supply 200, 120, 80 and 40 mg L-1. At 45, 65, 85, 105 and 140 days after transplant (DAT) of seedlings to the culture solution, the assessed physiological indexes were leaf area, leaf blade and total dry matter, and essential oil yield and chemical composition. To analyze gas exchange variables, an open portable photosynthesis system (LI-6400, Li-Cor Inc., NE, USA) was used to determine, at 65, 85 and 105 DAT, CO2 assimilation, transpiration, stomatal conductance, intercellular CO2 concentration and water use efficiency. For the assessments related to essential oil, extraction by hydrodistillation in Clevenger-type device was carried out to determine its yield and chemical composition through gas chromatography coupled to mass spectrometry. The obtained results indicated that the physiological indexes were influenced... (Complete abstract click electronic access below)

>Magister Scientiae - MSc / Salinity is one of the major limiting factors to crop production, which consequently contributes to the risk of reduced food security. Among other factors, food security depends on availability of sufficient and nutritious food for humans. Livestock such as cattle and sheep are fed with various plant-based feeds; with Medicago sativa (commonly known as alfalfa or lucerne) being a very important forage/feed crop, so much that it is regarded as the queen of forage crops. However, alfalfa is severely affected by high soil salinity and thus its growth and yield are drastically reduced in soils with high NaCl content. Among the various alfalfa genotypes/varieties examined in this study, Agsalfa was identified as salt tolerant because it performed better under salt treatment compared to Magna601.

In Arabidopsis thaliana, the development and the defense system are precisely controlled by some proteins to allocate energy and resources as needed. JASMONATE-ZIM domain 3 protein is the repressor of the jasmonic acid defense pathway. JACKDAW (JKD), SHORTSHOOT (SHR), and SCARECROW (SCR) bind together to form the BIRD complex, which regulates root patterning. The transcription factor Teosinte branched1/Cycloidea/Proliferating cell factor 14 (TCP14) also regulates plant development. Recent data shows that JAZ3 and TCP14 interact with JKD and may form a ternary complex, which reveals the study of the five proteins mentioned above may help to understand how defense signals are interpreted during plant growth. The interactions of these five proteins provide a theoretical base to maximize plant fitness and increase crop yield. Using protein purification, microscale thermophoresis, isothermal titration calorimetry, negative staining, X-ray crystallography in this project, we identified JKD interacted with JAZ3, and JKD interacted with TCP14, but they could not form a ternary complex in vitro; SHR/SCR interacted with JAZ3. Those binding results suggests TCP14 and SHR/SCR may have very similar binding site of JKD, and JAZ3 may guide the degradation of the BIRD complex. In structural studies, we resolved the 2D class average that showed the outline of the BIRD complex and it potentially helped to identify how JKD bound to DNA. We also determined the crystal structure of the TCP14 domain, which was an intertwined dimer that possibly uses arginine residues in the N terminus to interact with DNA. These interaction and structure studies of the five proteins provide the basis to understand how defense signals affect plant development.