Fundamental to the development of metazoa and plants is the capacity of cells to respond to transient intrinsic and extrinsic signals with permanent changes in gene expression that control cellular fates. A paradigmatic example of this process is observed in the case of the conserved, master regulatory HOX genes. The HOX genes are activated early in embryogenesis in combinatorial ON/OFF codes of expression, which act to specify and maintain segment identity in animals. In Drosophila, the “choice” of HOX code is controlled by transiently expressed transcription factors, while the “memory” of that choice is maintained in all future descendant cells through the action of the evolutionarily ancient Polycomb Group (PcG) gene family. The products of the PcG genes function in large, multimeric enzyme complexes known as Polycomb Repressive Complexes (PRCs) that are targeted to the HOX loci by cis-acting Polycomb Response Elements (PREs). Anchored at PREs, the PRCs catalyze a variety of chromatin modifications, most notably the trimethylation of histone H3 at lysine 27 (H3K27me3) by PRC2. These chromatin modifications are thought to both carry the memory of the HOX OFF code through DNA replication and to maintain transcriptional repression. In addition to the HOX genes, the PcG regulates hundreds of other important developmental control genes, the majority of which do not adopt heritable patterns of ON/OFF expression but instead are more dynamically expressed. This poses the question of how PcG activities control such diverse modes of gene expression. To investigate how PRE-anchored PRCs maintain heritable patterns of HOX gene expression, we have generated a transgenic lacZ reporter of the classical HOX gene Ultrabithorax (Ubx). Composed of minimal Ubx enhancer and promoter elements required to recapitulate the regulation of the native Ubx gene, the transgene contains the Ubx PRE embedded within a genetically labeled Flp-out cassette. H3K27me3 is deposited throughout the transgene in a manner that depends on the presence of the PRE. By excising the PRE in the cells of the wing imaginal disc where the transgene, like native Ubx, is heritably repressed, we are able to monitor the consequences of the loss of PRE-anchored PRC2 on both the inheritance of H3K27me3 and OFF state. We demonstrate that loss of the OFF state following PRE excision is correlated with the cell division-coupled dilution of H3K27me3. Further, by directly manipulating PRC2 activity of the H3K27 substrate, we demonstrate a causal relationship between the dilution of H3K27me3 nucleosomes and the number of times a cell can divide while maintaining the OFF state following PRE excision. In addition, we identified Ubx-lacZ transgene insertions that deviate from the classical patterns of heritable expression characteristic of the HOX genes in novel and informative ways. Our analysis of these insertions supports the view that PcG dependent chromatin modifications impose a quantitative rather than qualitative repressive influence on a gene’s promoter, with the promoter’s activity being determined within the context of other regulatory inputs. Similarly, contrary to classical view, we demonstrate that transcription too plays a quantitative role in determining whether or not a HOX locus adopts the heritable ON state. Together, our work suggests that the activities of the PcG confer a generic repressive influence on target loci. We posit that this influence is capable of maintaining heritable patterns of repression, as in the case of the HOX genes, because these loci have undergone stringent selection against enhancers capable of overcoming the repression mediated by the PcG. The absence of such strong activating inputs, together with the capacity of H3K27me3 to confer locus specific memory of the OFF state, allows for heritable patterns of repression. We propose that this is a special, albeit essential, attribute of the HOX genes. In contrast, most target genes have evolved to integrate repressive PcG chromatin modifications within the context of activating inputs that can override them. In these contexts, we propose that the PcG performs the role of a more general repressor, ensuring that repression is only overridden in those cells receiving peak activating cues. In this way the system may perform an essential role in conferring spatial and temporal robustness to gene expression programs.

Abstract not available

Orientador: Enes Furlani Júnior / Banca: Edson Lazarini / Banca: Marcio Lustosa Santos / Resumo: A cotonicultura de uma forma geral vem se destacando dentro do cenário mundial tanto pelo seu alto custo de produção, quanto por suas diversas formas de utilização da pluma pela população. O excessivo crescimento vegetativo pode interferir negativamente na produtividade, dessa forma, o uso de regulador de crescimento aplicado em função do desenvolvimento da cultura é essencial. O objetivo deste trabalho foi avaliar o comportamento do algodoeiro cultivado em região de Cerrado quando submetido ao tratamento com doses de regulador de crescimento via sementes e diferentes formas complementares de aplicação do produto via foliar. O delineamento experimental utilizado foi de blocos casualizados em esquema fatorial 5x3 com 15 tratamentos e 4 repetições, constituído por: 5 doses de cloreto de mepiquat (CM): 0, 4, 6, 8 e 10g i.a.kg-1 de sementes, aplicadas diretamente nas sementes de algodão; Manejo do regulador de crescimento via foliar com 250 mL ha-1: parcelada em quatro aplicações (35, 45, 55 e 65 dias após a emergência (d.a.e.)); aplicação única aos 70 d.a.e.; e sem a aplicação do produto. A cultivar utilizada foi a FMT 701, onde a utilização do CM em tratamento via sementes controla o desenvolvimento em altura do algodoeiro de forma linear até os 60 d.a.e., e promove redução do diâmetro caulinar no período inicial da cultura. A aplicação foliar de CM tanto de forma única como parcelada reduz o porte das plantas. A aplicação parcelada proporciona aumento dos teores foliares de N e Mg e as maiores produtividades de algodão em caroço são encontradas para dose de 4g i.a.kg-1 de sementes / Abstract: The cotton crop in general has been outstanding in the world scene as much for its high production cost, and by its various forms for use by the population of the plume. The excessive vegetative growth can interfere negatively on productivity, thus, the use of growth regulator applied with the development of the culture is essential. The objective of this study was to evaluate the behavior of cotton crop grown in the Cerrado region when exposed to treatment with levels of growth regulator through seeds and different complementary forms of foliar application of the product. The experimental design was randomized block in a 5x3 factorial design with 15 treatments and 4 replications, consisting of: 5 levels of mepiquat chloride (MC): 0, 4, 6, 8 and 10 a.i. kg-1 seeds, applied directly in cotton seeds; management of foliar growth regulator with 250mL ha-1: split in four applications (35, 45, 55 and 65 days after emergence (d.a.e.)); single application at 70 d.a.e., and without product application. The cultivar was FMT 701. The use of MC to seeds controls the development in height of cotton linearly until 60 d.a.e., and promotes the stem diameter reducing in the early period of culture. The foliar application of MC, unique way and split application reduces the size of the plants. The split application provides increased foliar N and Mg and the highest yield of cotton are found to level of 4g a.i. kg-1 seeds / Mestre

Made available in DSpace on 2014-06-11T19:29:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-16Bitstream added on 2014-06-13T18:39:31Z : No. of bitstreams: 1 ferrari_jv_me_ilha.pdf: 327876 bytes, checksum: 7e4ad803907cfd694552424946e0e07b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A cotonicultura de uma forma geral vem se destacando dentro do cenário mundial tanto pelo seu alto custo de produção, quanto por suas diversas formas de utilização da pluma pela população. O excessivo crescimento vegetativo pode interferir negativamente na produtividade, dessa forma, o uso de regulador de crescimento aplicado em função do desenvolvimento da cultura é essencial. O objetivo deste trabalho foi avaliar o comportamento do algodoeiro cultivado em região de Cerrado quando submetido ao tratamento com doses de regulador de crescimento via sementes e diferentes formas complementares de aplicação do produto via foliar. O delineamento experimental utilizado foi de blocos casualizados em esquema fatorial 5x3 com 15 tratamentos e 4 repetições, constituído por: 5 doses de cloreto de mepiquat (CM): 0, 4, 6, 8 e 10g i.a.kg-1 de sementes, aplicadas diretamente nas sementes de algodão; Manejo do regulador de crescimento via foliar com 250 mL ha-1: parcelada em quatro aplicações (35, 45, 55 e 65 dias após a emergência (d.a.e.)); aplicação única aos 70 d.a.e.; e sem a aplicação do produto. A cultivar utilizada foi a FMT 701, onde a utilização do CM em tratamento via sementes controla o desenvolvimento em altura do algodoeiro de forma linear até os 60 d.a.e., e promove redução do diâmetro caulinar no período inicial da cultura. A aplicação foliar de CM tanto de forma única como parcelada reduz o porte das plantas. A aplicação parcelada proporciona aumento dos teores foliares de N e Mg e as maiores produtividades de algodão em caroço são encontradas para dose de 4g i.a.kg-1 de sementes / The cotton crop in general has been outstanding in the world scene as much for its high production cost, and by its various forms for use by the population of the plume. The excessive vegetative growth can interfere negatively on productivity, thus, the use of growth regulator applied with the development of the culture is essential. The objective of this study was to evaluate the behavior of cotton crop grown in the Cerrado region when exposed to treatment with levels of growth regulator through seeds and different complementary forms of foliar application of the product. The experimental design was randomized block in a 5x3 factorial design with 15 treatments and 4 replications, consisting of: 5 levels of mepiquat chloride (MC): 0, 4, 6, 8 and 10 a.i. kg-1 seeds, applied directly in cotton seeds; management of foliar growth regulator with 250mL ha-1: split in four applications (35, 45, 55 and 65 days after emergence (d.a.e.)); single application at 70 d.a.e., and without product application. The cultivar was FMT 701. The use of MC to seeds controls the development in height of cotton linearly until 60 d.a.e., and promotes the stem diameter reducing in the early period of culture. The foliar application of MC, unique way and split application reduces the size of the plants. The split application provides increased foliar N and Mg and the highest yield of cotton are found to level of 4g a.i. kg-1 seeds

Understanding the biotic factors influencing invasive plant performance is essential for managing invaded land and preventing further exotic establishment and spread. I studied how competition between both conspecifics and native co-habitants and arbuscular mycorrhizal fungal (AMF) impacted the success of the invasive bunchgrass Brachypodium sylvaticumin early growth stages. I examined whether invasive plants performed and competed differently when grown in soil containing AMF from adjacent invaded and noninvaded ranges in order to determine the contribution of AMF to both monoculture stability and spread of the invasive to noninvaded territory. I also directly manipulated common mycelial network (CMN) formation by AMF to determine hyphal network contribution to competitive interactions. I found that invasive plants performed most poorly (as indicated by decreased chlorophyll content, size and shoot dry mass) in invaded range soil against conspecifics. This could be two-pronged evidence for existing biotic pressure on the invasives to expand into adjacent noninvaded ranges. I also found a negative effect of AMF colonization and invasive plant performance, potentially indicating deleterious plant-soil feedbacks which could help maintain plant biodiversity at a community level. CMN effects were found to be interactive with root competition and directly affected the performance and nutrient status of B. sylvaticum. Although no direct correlations between AMF colonization levels and competition were found, CMN presence contributed significantly to plant growth and nutrient status. Therefore AMF, through infection and CMN formation, may be able to influence invasive plant growth and spread in the field.

Thesis (M.Sc.(Plant Protection)) -- University of Limpopo, 2022 / Runner beans are extremely sensitive to root-knot (Meloidogyne species) nematodes. Phytonematicides had been consistently used in managing population densities of Meloidogyne species in various crops, with the application technologies being restricted to the ground leaching technology (GLT) and botinemagation technology, each with its own advantages and disadvantages. The use of seeds as carriers of active ingredients of phytonematicides and then drying prior to sowing, is being considered as another potential application strategy in seeds with hypogeal germination. In such seeds, during seedling emergence the seed cover and the endosperm remain below the soil surface, just above the developing root system. As a result, in phytonematicide-primed seeds, the seed structures could serve as carriers for the active ingredients of phytonematicides. In cucurbitacin phytonematicides, Nemarioc-AL and Nemafric-BL phytonematicides contain cucurbitacin A and B, respectively as active ingredients. The objectives of the study were two-fold, namely, to determine whether runner bean (Phaseolus coccineus L.) seeds would (1) serve as carriers of active ingredients of cucurbitacin-containing phytonematicides without affecting seed germination under in vitro conditions, (2) serve as carriers of cucurbitacins intended for suppression of M. incognita population densities under greenhouse and microplot conditions. Two separate studies were conducted under laboratory conditions, with seven treatment solutions at 0, 2, 4, 8, 16, 32 and 64% Nemafric-BL or Nemarioc-AL phytonematicide. After exposure to separate solutions for 2 h, runner bean seeds were dried on laboratory benches for 72 h. Treatments were arranged in a completely randomised design (CRD), with 8 replications. Two layers of filter papers were placed inside each Petri dish seeded with 10 primed and dried seeds. Petri dishes were incubated inside LABCON growth chamber at 25ºC and 75% relative humidity. Successful seed germination, viewed as emergence of radicle from the testa, was recorded daily for a period of 10 days, with each count being removed from Petri dish to avoid re-counting. Under greenhouse and microplot conditions, primed-and dried seeds were sown in plastic pots containing 2 700 ml steam-pasteurised sandy loam soil, arranged in a randomised complete block design, replicated six times and eight times, respectively. Each seedling was inoculated by distributing 5 000 eggs and second-stage juveniles (J2) of M. incognita race 4 using a 50 ml plastic syringe. Originally, pots were irrigated using 500 ml chlorine-free tapwater, which was reduced to half after seedling emergence at every other day. Plant variables were collected at 56 days after inoculation and data were subjected to the Curve-fitting Allelochemical Response Dose algorithm model. In vitro, germination percentage (R 2 = 0.96), radicle length (R 2 = 0.89) and plumule diameter (R 2 = 0.96) versus Nemarioc-AL phytonematicide exhibited positive quadratic relations. Similarly, the variables versus Nemafric-BL phytonematicide, exhibited positive quadratic relations. In vitro, Mean Concentration Stimulation Point (MCSP) value of Nemarioc-AL phytonematicide on runner bean seeds was 1.05%, whereas for Nemafric-BL phytonematicide MCSP value was 0.58%. Under greenhouse conditions, plant height (R 2 = 0.97), chlorophyll content (R 2 = 0.92), dry shoot mass (R 2 = 0.98), dead nodule number (R 2 = 0.90), total pod number (R 2 = 0.97) and active nodule number (R 2 = 0.93) versus Nemarioc-AL phytonematicide exhibited positive quadratic relations., Similarly, chlorophyll content (R 2 = 0.95), gall rating (R 2 = 0.82), dry shoot weight (R 2 = 0.69), stem diameter (R 2 = 0.85) and total nodule number (R 2 = 0.86) versus Nemafric-BL phytonematicide exhibited positive quadratic relations. Under greenhouse conditions, MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides were 4.18 and 3.69%, respectively. Under microplot conditions, total number of nodules (R 2 = 0.88), number of nodules dead (R 2 = 0.99), number of nodules active (R 2 = 0.95), fresh root mass (R 2 = 0.99), and fresh pod mass (R 2 = 0.99) versus Nemarioc-AL phytonematicide, exhibited positive quadratic relations, whereas plant height (R 2 = 0.85), number of nodules dead (R 2 = 0.87), dry shoot mass (R 2 = 0.97), fresh root mass (R 2 = 0.97) and total number of nodules (R 2 = 0.63) versus Nemafric-BL phytonematicide exhibited positive quadratic relations. Under microplot conditions, MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides were 3.76 and 3.93%, respectively, each with ∑k = 0. All degrees of Nemarioc-AL and Nemafric-BL phytonematicides profoundly reduced nematode numbers under greenhouse and microplot trials. Based on the information obtained from this study, it was confirmed that runner bean (P. coccineus) is sensitive to Nemafric-BL and Nemarioc-AL phytonematicides supported by the Curve-fitting Allelochemical Response Dose (CARD) model results due to most plant variables that had sensitivity values of zero. In conclusion, the priming technology should be developed further since it has the potential of being successful in nematode management in seeds with hypogeal germination / National Research Foundation (NRF) and Potatoes South Africa

TCP4 as an integrator of key developmental events A striking aspect of plant life is their sedentary life-style. Though it relieves them of the obligation of forming a complex body organization, it exposes them to environmental challenges. Plants have evolved a flexible pattern of post-embryonic growth. The major phases in their life cycle are photomorphogenesis, vegetative growth with phase transitions, reproductive growth and senescence. The phase transitions are coordinated temporally to ensure proper maturation of organism. Flexibility is built in the re-iterated programs of organogenesis, which provides a plant with an option to adopt an architecture best suited to prevailing environmental conditions. Organogenesis occurs by processes of cell division and maturation (expansion). Cell division determines the growth potential by generating the requisite number of cells and cell maturation fulfils the potential by elaborating the organ form. Organ growth requires spatially- and temporally-controlled cellular maturation. The TCP class of plant-specific transcription factors, conserved from bryophytes to angiosperms, control diverse developmental and morphological traits, such as plant architecture, floral asymmetry, seed germination, male and female gametophyte development and photomorphogenesis (Martín-Trillo and Cubas, 2010). Class II TCPs, which are targets of miR319, are best known for their role in leaf morphogenesis. They are believed to function by redundantly regulating the onset of cellular maturation ( Efroni et al., 2008; Koyama et al., 2007; Nath et al., 2003; Ori et al., 2007; Palatnik et al., 2003; Schommer et al., 2008). To establish the link between level of TCP activity and organ growth, we undertook the approach of hyper-activating the function of TCP4, a representative class II TCP, by fusing it with a strong transactivation domain. Enhanced level of TCP4 activity reduced organ growth by causing precocious cellular maturation. It also accelerated the process of organ initiation, maturation and its progression into the final stage of senescence. Hyper-active TCP4-expressing plants underwent faster maturation of shoot apex into reproductive phase. In general, hyper-activation of TCP4 advanced cellular, organ and organism maturation programs in Arabidopsis life cycle (Fig. 1). Traits such as organ initiation rate, organ size, flowering time and seed yield contribute to the fitness of the plant. Faster rate of organ initiation, bigger organ size, early onset of flowering and higher seed yield are obvious desirable traits. However, they rarely occur simultaneously in a mutant or a natural variant, suggesting that there is a trade-off among different traits. Studies have shown that such traits are linked and are controlled by multiple loci that contribute quantitatively to the phenotype. A change that benefits one trait may adversely affect another (Colautti et al., 2011; Kozlowski, 1992; Mendez-Vigo et al., 2010) . Our study shows that TCP4 activity can potentially coordinate these inter-connected traits. Though hyper-active TCP4-expressing plants have faster rate of organ initiation, the final organ size is reduced and senescence is advanced. These plants reach reproductive phase faster, but produce fewer seeds, hence limiting their propagation and lowering their fitness in comparison to the wild type. Such a genetic constraint on the traits limits the phenotypic variation that can be produced in plants and, hence, their adaptation to the environment. Our study suggests that TCP4 can link organ growth with that of the whole organism. It acts as a heterochronic regulator which possibly affects timing of multiple maturation programs. Any perturbation in the TCP activity may have far-reaching effects on plant growth and thus, optimal level of TCP activity is crucial for plant homeostasis. One possible explanation for the developmental pleitropy in TCP4 hyper-activation line is an alteration in hormone biosynthesis or sensitivity. A combination of microarray and hormone application studies on hyper-active TCP4-expressing line has indicated a reduction in the levels of GA and auxin and an increase in cytokinin and MeJA levels. There may also be an inhibition of auxin signaling and upregulation of MeJA and ethylene signaling. In addition, TCP4 appeared to regulate both GA biosynthesis and response in opposing manner. The molecular mechanisms involved in TCP4-mediated integration of hormonal pathways are still unclear. Answering these questions would require identification of its direct downstream targets.

TCTP (Translationally Controlled Tumor Protein) est une protéine très conservée chez l'ensemble des eucaryotes. C’est une protéine vitale impliquée dans divers processus essentiels, et pour de nombreux organismes son absence conduit à la létalité dès les stades embryonnaires.Chez les animaux comme chez les végétaux, TCTP joue un rôle primordial dans la croissance et le développement des individus. En plus de son implication dans l’apoptose et la réparation de l’ADN, TCTP favorise la prolifération cellulaire, et se trouve donc être un élément important de la tumorigenèse. Chez les végétaux, la forte conservation de TCTP a permis la préservation de la plupart des fonctions décrites chez les animaux, mais les facteurs qui interviennent en amont ne sont pas encore connus.Par la mise en place, la conduite et la finalisation de deux cribles génétiques utilisant la plante modèle Arabidopsis thaliana, ce travail de thèse a cherché à identifier des facteurs situés en amont de TCTP. En parallèle, une seconde étude fut menée afin de mesurer l'impact de l'absence de TCTP sur les voies de l’auxine et des cytokinines au cours du développement embryonnaire, permettant de mieux comprendre l’origine de l’embryolétalité du mutant tctp. / TCTP (Translationally Controlled Tumor Protein) is strongly conserved among eukaryotes. It is a vital protein implicated in various major processes, and its absence leads to early embryolethality in many organisms. In plants as in animals, TCTP is a key factor of growth and development. Implicated in apoptosis and DNA repair, TCTP is also an enhancer of cell proliferation, and is a key element of tumorigenesis. Major functions of TCTP are conserved between plants and animals, but upstream factors are not known yet. Using a genetic screen on the model plant Arabidopsis thaliana, the principal goal of this thesis was to discover regulators of TCTP.In parallel, the impact of TCTP knockout on auxin and cytokinin pathways during embryo development was investigated.