Submitted by LUANA JANDHY MANTOVANINI (lumantovanini@gmail.com) on 2017-08-29T19:11:30Z No. of bitstreams: 1 Dissertação_Luana_Jandhy_Mantovanini.pdf: 1646514 bytes, checksum: 4c536d5f2d4ac50ce5a852c9b10ce27c (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-08-29T19:18:01Z (GMT) No. of bitstreams: 1 mantovanini_lj_me_jabo.pdf: 1646514 bytes, checksum: 4c536d5f2d4ac50ce5a852c9b10ce27c (MD5) / Made available in DSpace on 2017-08-29T19:18:01Z (GMT). No. of bitstreams: 1 mantovanini_lj_me_jabo.pdf: 1646514 bytes, checksum: 4c536d5f2d4ac50ce5a852c9b10ce27c (MD5) Previous issue date: 2017-05-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A cana-de-açúcar é atualmente uma das principais culturas da agroindústria mundial. Devido à ampla expansão de seu plantio é submetida constantemente a solos não produtivos. A presença de moléculas tóxicas no solo, como o alumínio (Al3+), interfere diretamente no desenvolvimento radicular ocasionando baixa absorção de água e nutrientes levando a pouca produtividade e desenvolvimento das plantas. Os microRNAs tem sido descritos como um dos fatores responsáveis pela regulação gênica e a descoberta dessas moléculas abre um novo caminho para a elucidação da tolerância e adaptação das plantas aos estresses abióticos. Este estudo visou avaliar em duas cultivares de cana-de-açúcar (CTC-2 e RB855453) a expressão dos microRNAs miR159, miR164 e miR168, associados à resposta ao alumínio em espécies como Arabidopsis thaliana, arroz (Oriza sativa) e tabaco (Nicotiana tabacum). Algumas características foram avaliadas, como densidade de raízes (DS), área foliar (AR), produção de massa seca (MS) e teor de prolina nas folhas, em quatro cultivares de cana-de-açúcar submetidas a diferentes concentrações de alumínio. A cultivar CTC 2 foi classificada como tolerante e a RB855453 como sensível ao estresse. Ambas foram selecionadas e em sistema de hidroponia submetidas novamente ao estresse pela toxidez de alumínio na concentração de 221 μmol L -1 . Parâmetros fisiológicos foram mensurados (área foliar, potencial osmótico, taxa de fotossíntese, transpiração, condutância estomática) e a expressão dos miRNAs 159, 164 e 168 avaliada por PCR em tempo real. Plantas das duas cultivares apresentaram alterações fisiológicas e morfológicas ao longo do estresse, com redução significativa para a área foliar da cultivar RB855453. O miR164 e 159 foram induzidos nas duas cultivares, principalmente após 72 horas de estresse, e o miR168 diferencialmente expresso. Esses miRNAs regulam genes e fatores de transcrição que estão envolvidos na resposta e desenvolvimento da planta diante ao estresse por alumínio. / The sugarcane is currently one of the main crops of global agribusiness. Due to the wide expansion of its plantation is constantly subjected unproductive soils. The presence of toxic molecules in the soil, such as aluminum (Al3+), directly affects root development, leading to poor absorption of nutrients and water leading to low productivity and development of plants. Studies of the interactions of plants with the environment are being conducted to clarify the resistance or susceptibility of various cultures, favoring the discovery of important mechanisms that participate in physiological and molecular responses to environmental stresses. MicroRNAs have been described as one of the factors responsible for gene regulation and the discovery of these molecules opens a new path for the elucidation of tolerance and adaptation of plants to abiotic stresses. This study evaluated in two sugarcane varieties the expression of microRNA miR159, miR164 and miR168, associated with the response to the aluminum species such as Arabidopsis thaliana, rice (Oryza sativa) and tobacco (Nicotiana tabacum). Some characteristics were evaluated, such as density (DS), area (AR), dry mass production (DM) and proline content, in four sugarcane cultivars submitted to different concentrations of aluminum. CTC 2 cultivar was classified as tolerant and RB855453 as stress sensitive. Both were selected and in a hydroponics system again submitted to stress by the aluminum toxicity in the concentration of 221 μmol L-1. Physiological parameters were measured (leaf area, osmotic potential, photosynthesis rate, transpiration, stomatal conductance) and the expression of miRNAs 159, 164 and 168 evaluated by real-time PCR. Plants of both cultivars presented physiological and morphological changes along the stress, with a significant reduction for the leaf area of cultivar RB855453. The miR164 and 159 were induced in the two cultivars, mainly after 72 hours of stress, and the miR168 differentially expressed. These miRNAs regulate genes and transcription factors that are involved in the response and development of the plant in the face of aluminum stress.

Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-04-06T19:10:05Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) 2012-Dissertacao-CinthyaPacheco.pdf: 4196314 bytes, checksum: 681027684434d14d4010bb477d291988 (MD5) / Made available in DSpace on 2017-04-06T19:10:06Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) 2012-Dissertacao-CinthyaPacheco.pdf: 4196314 bytes, checksum: 681027684434d14d4010bb477d291988 (MD5) Previous issue date: 2012-03-02 / A salinidade dos solos é um fator limitante para o desenvolvimento da cultura da cana-de-açúcar no Brasil, porém as plantas em geral apresentam mecanismos de tolerância variável ao estresse por salinidade. Nestes, pode haver alterações na expressão gênica que se tornam importantes objetos de estudo, que pode ser realizado através de análise proteômica. Assim,o objetivo do trabalho foi identificar peptídeos diferencialmente expressos em plantas de cana-de-açúcar submetidas ao estresse salino. Para tal, foi conduzido experimento em casa de vegetação com quatro variedades de cana-de-açúcar (RB867515, RB92579, RB72454 e RB855536) e duas condições salinas, 0 mM (controle) e 200 mM de NaCl. As coletas foram realizadas após 2 e 72 h da indução ao estresse por sal, tanto para as análises fisiológicas quanto para a análise proteômica. Os parâmetros fisiológicos avaliados foram: vazamento foliar de eletrólitos, potencial hídrico foliar, teor relativo de água, transpiração, fotossíntese e condutância estomática. Para a análise proteômica,as proteínas totais da folha +1 e raízes foram extraídas, quantificadas e analisadas por eletroforese bidimensional. A análise das imagens dos géis foi realizada em programa computacional onde em cada contraste apenas uma variável foi considerada (condição salina ou variedade). Spots diferenciais foram excisados, digeridos com tripsina e somente os de raiz foram identificados via espectrometria de massas. De acordo com os parâmetros fisiológicos, foram selecionadas as variedades RB855536 como a mais sensível à salinidade e a RB867515 como a mais tolerante. Foram observados peptídeos diferencialmente expressos distribuídos nos contrastes em ambas as variáveis (condição salina ou variedade) e órgãos estudados, categorizados por processo biológico e função molecular através de sua ontologia gênica.A variedade tolerante (RB867515) mostrou maior acúmulo de proteínas envolvidas com crescimento, desenvolvimento, metabolismo de carboidratos e energético após 2 h de estresse,indicando que nessas plantas a detecção do fator de estresse parece ativar sinalização para continuar o crescimento radicular, evitando regiões com excesso de íons tóxicos. Por outro lado, foi verificada na variedade sensível a presença dessas proteínas apenas no tratamento após 72 h. Em adição, proteínas envolvidas na metabolização de radicais livres, proteção de proteínas e estabilização de membranas tiveram sua expressão induzida na fase inicial de exposição ao estresse na variedade tolerante, enquanto que na sensível essas proteínas só foram expressas no tratamento após 72 h. Tais resultados sugerem que essas vias de resposta ao estresse são mais eficientes para conferir maior tolerância à salinidade em cana-de-açúcar, e que sua efetividade para a tolerância fenotípica depende da detecção do estresse e ativação precoce da expressão dos genes codificantes. / Soil salinity is a limiting factor to sugarcanecrop development in Brazil, although in general plants present variable mechanisms of tolerance to salinity stress. In these, gene expression changes become important study focus, that can be performed through proteomic analysis. Thus, the objective of this work was to identify differentially expressed peptides in sugarcane plants submitted to salinity stress. For that, a greenhouse experiment was established with four sugarcane varieties (RB867515, RB92579, RB72454 and RB855536) and two salt conditions, 0mM (control) and 200 mM NaCl. Harvests occurred after 2 and 72 h of stress induction by salt, for physiological analyses as well as for proteomics.The evaluated physiological parameters were: leaf electrolytes leakage, leaf water potential, relative water content, transpiration, photosynthesisand stomatal conductance. In proteomic analysis, total proteins from leaf and roots were extracted, quantified and analysed through bidimensional electrophoresis. Gel images analyses were done computational program,where in each contrast only one variable was considered (salinity conditionor variety). Differential spotswere excised, digested by trypsin and only the root-derived were identified via mass spectrometry.According to the physiological parameters, were selected the varieties RB855536 as the most sensitive to salinity, and the RB867515 as the most tolerant. Differentially expressed peptides were observed distributed in the contrasts in both variables (salinity condition or variety) and sampled organs, organised in gene ontology categories by biologicalprocess and molecular function. Tolerant variety (RB867515) showed the highest accumulation of proteins involved in growth, development, carbohydrate and energy metabolism after 2 h of stress, indicating that in such plants the detection of stressing factor seems to activate signaling pathways towards keeping root growth, avoiding regions with toxic ions excess. On the other hand, the presence of these proteins in the sensitive variety was verified only in treatment after 72 h.In addition, proteins involved in free radicals metabolization, protein protection and membrane stabilization had their expression induced in the initial phase of stress exposure in tolerant variety, while in sensitive one these proteins were expressed only in treatment after 72h. Such results suggest that these stress response pathways are more efficient to confer higher tolerance to salinity in sugarcane, and their effectiveness for phenotypical tolerance depends on stress detection and early activation of the coding genes expression.

Abiotic stresses such as salt stress are the major limiting factors for agricultural productivity, and cause global food insecurity. It is well known that plant associated beneficial microorganisms can stimulate plant growth and enhance resistance to abiotic stresses. In this context, bacterial endophytes are a group of bacteria that colonize the host plant and play a fundamental role in plant growth enhancement under stress condition. Recently, our group reported that the beneficial bacteria Enterobacter sp.SA187 induces plant growth in Arabidopsis under salt stress conditions by manipulation of the plant ethylene signaling pathway. We therefore compared inoculation of plants by SA187 with virulent and non-virulent strains Pst DC3000. Although both strains inhibit plant growth at ambient conditions, Pst DC3000 hrcC-, but not Pst DC3000, induced salt stress tolerance, suggesting that Pst DC3000 hrcC- also contains plant growth promoting activity under stress conditions. Our results indicate that Pst DC3000 hrcC- shares features with beneficial bacteria by inducing salt tolerance through reduction of the shoot and root Na+/K+ ratio. To further elucidate the underlying mechanisms of this interaction with Arabidopsis, RNAseq, hormone and biochemical analyses were performed. Genetic studies also show that Pst DC3000 hrcC- induced salt stress tolerance involving several phytohormone pathways, including auxin, ethylene and salicylic acid. Transcriptome and genetic analyses indicate that glucosinolates play an important role in this beneficial interaction. We found that indolic and alkyl glucosinolates act as negative factors on Pst DC3000 hrcC-, alkyl glucosinolates are positive and indolic glucosinolates negative regulators in SA187 interaction with Arabidopsis. These results reveal that besides a repertoire of effectors, Pst DC3000 hrcC- also produces factors that can be beneficial for plant growth under certain stress conditions, as observed with Enterobacter sp. SA187.

No description available.

Abiotic stress leads to a change in the water content of plants. Salinity and osmotic stress affect both the morphology and physiology of plants. Plants have therefore responded to these environmental changes by adapting and tolerating them. The SABP2-interacting proteins (SIP) 428-silenced RNAi transgenic tobacco lines were subjected to various abiotic stresses (salinity, osmotic, and drought). The effect of SIP428-silencing on the tobacco plants subjected to these abiotic stresses was monitored. The results from the root growth data show that the sip428-silenced lines exhibit enhanced tolerance to the stressors compared to the wild-type plants. Interestingly, results of the relative chlorophyll content show no significant difference between the wild-type plants and sip428-silenced transgenic plants. In summary, based on the results presented in this study it could be concluded that SIP428 is a negative regulator of salinity, osmotic and drought stresses. Further studies are required to understand the mechanism.

Plants had to evolve, due to their sessile growth habit, a complex system of defence against adverse environmental conditions. Plant abiotic stress responses are regulated by plant hormones, especially by cytokinins (CKs) and abscisic acid (ABA). In order to evaluate the effect of enhanced stress tolerance on the dynamics of hormones (CKs, auxin and ABA) as well as polyamine levels during the drought and/or heat stress (HS) progression, response of tobacco plants with enhanced level of osmolyte proline was compared with the corresponding wild-type. HS (40řC) caused a transient increase in bioactive CK content, accompanied by decrease of ABA, which indicated stimulation of transpiration, important mechanism to cool down the leaf temperature at the early phase of HS. Simultaneously, a transient increase in spermidine and spermine levels was found, more profound in proline-over-producing transformant. The activities of particular polyamine metabolic enzymes correlated well with their content. Drought stress resulted in the establishment of a gradient of bioactive CKs in favour of the upper leaves, crucial for their preferential protection. Application of HS at the end of drought period strongly enhanced the stress severity, mainly due to additional water loss caused by enhanced transpiration....

Abiotic stresses are constantly rising and pose a very high risk to global agricultural productivity and food security. Some plants have evolved several innate pathways for defense against these stresses. Hence, understanding stress signaling pathways can help develop crop plants with higher stress tolerance. The salicylic acid-mediated signaling pathway is important in plants experiencing biotic and abiotic stresses. In previous studies, SABP2-Interacting Protein (SIP-428) has been shown to be a negative regular of plant growth under abiotic stress. This study aimed to investigate the roles of SIP-428 in the ROS signaling of tobacco plants. We investigated transgenic RNAi-silenced lines of SIP-428 and wild-type tobacco plants for the activities of guaiacol peroxidase and catalase enzymes in Mannitol and NaCl-stressed plants for 7 and 14 days. Our results showed that SIP-428 plays a significant role in ROS signaling in Mannitol and NaCl-stressed plants via the activities of guaiacol peroxidase.

Drought and temperature stress are the two most important factors limiting crop productivity. A physiological and proteomic analysis of soybean was performed to investigate the negative impact of these variables. The previous studies reported the beneficial effect of silicon under stress conditions. Silicon supplementation may promote plant growth under drought stress, although the mechanism to alleviate drought stress is uncertain. The proteomic analysis of chloroplast proteins was carried out to study the response of silicon supplementation under drought stress. Similarly, temperature stress, mainly heat stress, has an adverse effect on soybean plants. The comparative analysis of two soybean cultivars, DS25-1 and DS31-243 was examined under ambient and elevated CO2 levels. The proteomic study employed two-dimensional gel analysis and mass spectrometry techniques to identify differentially expressed proteins under drought and temperature stress. The identified proteins are involved in metabolic processes, photosynthesis, signaling, redox homeostasis, and other cellular pathways. Most of these proteins were involved in metabolism, response to heat and photosynthesis showing significant cross-tolerance mechanisms. The physiological parameters like stomatal conductance, transpiration, photosynthesis, and chlorophyll pigments were also studied. Silicon application improved plant growth under drought stress. However, at the elevated CO2 level, plants showed better growth under heat stress. Together, these findings suggested the role of silicon and elevated CO2 concentration in drought and temperature stress in soybean. The differentially expressed proteins helped mitigate the negative impact of these stress, mainly the photosynthetic, antioxidant and heat shock proteins, and enhance crop growth and productivity under drought and heat stress.

Global climate change is identified as a major threat to the survival of natural ecosystems. The variations in global climate have gained the attention of researchers worldwide, as these changes negatively affect agriculture by reducing crop productivity and food security.  Projects related to abiotic stress tolerance are significant because they address important challenges facing agriculture and food security, contribute to more sustainable agricultural practices, and advance our understanding of fundamental plant biology. Some plants have defense mechanisms that are activated upon receiving stress stimuli to increase systemic tolerance to abiotic stresses such as heat, light, and cold. Salicylic acid-binding protein 2 (SABP2) from tobacco exhibits a high affinity for salicylic acid (SA) and is an important component in the SA-signaling pathway. SABP2 interacts with other cellular proteins to initiate downstream signaling and activate responses leading to resistance. Several SABP2-interacting proteins (SIP), including SIP-428, have been identified. The main goal of this proposed research is to determine the role of SIP-428 in mediating environmental stresses. SIP-428 is a SIR2-type non-histone deacetylase enzyme. De/acetylation is a common post-translational modification of proteins in eukaryotes. Since SIP-428 is a SABP2-interacting protein, it is involved in plant immune signaling. To determine the role of SIP-428 in plant physiology, it was biochemically characterized, and transgenic tobacco plants silenced in SIP-428 expression were previously generated and analyzed. Transgenic tobacco plants overexpressing SIP-428 were also generated. These lines expressed SIP428 at higher levels upon treatment with estradiol. Transgenic tobacco that overexpresses SIP-428 has been used in this study. To test the role of SIP428 in abiotic stress, the transgenic plants will be treated with abiotic stress-inducing chemicals, e.g. NaCl (salinity stress), mannitol (osmotic stress), and PEG6000 (drought stress). The treated seedlings will be allowed to grow for a specific time (1-2 weeks). The expression of SIP-428 will be monitored by western blotting (using anti-myc antibodies). The effects of SIP-428 expression on abiotic stress tolerance will be investigated biochemically by examining the activities of antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). Additionally, gene expression analysis will also be conducted to determine the expression of antioxidant genes.

<p> Abiotic stresses such as extreme temperatures, drought and high salinity severely compromise plant productivity, and have placed selective pressure for the acquisition of traits enabling plants to adjust to and recover from these unfavorable environmental conditions. Thellungiella salsuginea is a plant that is native to highly saline and semiarid environments and exhibits an exceptional ability to tolerate abiotic stress. In this thesis, I report on laboratory and field studies aimed at identifying traits that allow Thellungiella to tolerate harsh environmental conditions. It was found that Thellungiella accumulates organic solutes in response to abiotic stress. Transcript and metabolite profiling approaches were used to identify metabolic pathways important for the accumulation of compatible organic solutes in Thellungiella in response to sub-optimal environmental conditions. The relative abundance of transcripts encoding enzymes associated with the biosynthesis of compatible organic solutes such as proline or galactinol showed stress-responsive increases in cabinet-grown material and these metabolites were accumulated in salt or drought treated plants, respectively. However, proline and galactinol were found to be of low relative abundance in leaves of field plants. In contrast, several carbohydrates including sucrose, glucose, and fructose made a greater relative contribution to the field plant profiles suggesting that carbohydrates play an important role in plant abiotic stress tolerance during growth under field conditions. The identification of stress-specific metabolic changes can be used to identify important biochemical traits underlying environmental stress tolerance in Thellungiella. This information can be used to improve the tolerance of stress -sensitive crops (including a related crucifer species, canola) that are grown in areas where persistent droughts, saline soils and early or late frosts frequently occur. </p> / Thesis / Doctor of Philosophy (PhD)