Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
Navegar
8 resultados
Resultados da Pesquisa
Item Efeitos da superexpressão do microRNA156 sobre a morfofisiologia de Passiflora edulis Sims. durante a transição de fase juvenil/adulta(Universidade Federal de Viçosa, 2020-03-02) Soares, Jéssica Ribeiro; Otoni, Wagner Campos; http://lattes.cnpq.br/3191746929406319Item The role of NAD+ compartmentation and dynamics in Arabidopsis thaliana(Universidade Federal de Viçosa, 2020-02-19) Araujo, Elias Feitosa; Nesi, Adriano Nunes; http://lattes.cnpq.br/4607484418104157Nicotinamide adenine dinucleotide (NAD+) is a fundamental coenzyme required to regulate plant central metabolism and redox status homeostasis. Plants produce NAD+ via de novo and salvage pathways. Despite early steps of the two pathways occur in different subcellular compartments, de novo in chloroplasts and salvage in cytosol, both pathways produce the final product NAD+ exclusively in the cytosol. Thus, NAD+ must be imported into organelles to drive biological processes inside them. In Arabidopsis thaliana, three genes have been identified as NAD+ carriers, namely NDT1 (At2g47490) and NDT2 (At1g25380), both targeted to the inner mitochondrial membrane, and the peroxisomal transporter PXN (At2g39970). The previous functional characterization of NDT1, NDT2 and PXN have revealed their importance for seed production and quality, seedling establishment, photosynthesis, metabolism, stomatal density and stomatal conductance. To extend our knowledge on the importance of NAD+ dynamics, we used mutants for NAD+ transport and focused in comprehend: (1) how altered NAD + distribution affects stomatal development in cotyledons, (2) the crosstalk between NAD+ transport and elevated atmospheric CO2 concentration and (3) NAD + dynamics in vivo under different environmental cues. The results indicate that NAD negatively regulates stomatal development in cotyledons of Arabidopsis. Seedlings with reduced expression of mitochondrial (NDT1 and NDT2) and peroxisomal (PXN) NAD+ transporter genes displayed reduced numbers of stomata lineage cells and reduced stomatal density. Furthermore, cotyledons of wild- type seedlings treated with exogenous NAD+ and cotyledons of mutant plants with reduced NAD+ breakdown capacity also exhibited reduced stomatal number. Impaired NAD+ transport and the exogenous NAD+ feeding were further associated with the induction of abscisic acid (ABA)-responsive genes. Additionally, NAD+ feeding of aba- 2 and ost1 seedlings, impaired in ABA synthesis and ABA signaling, respectively, did not impact on stomatal number, whereas the inhibition of ABA synthesis rescued the stomatal phenotype in NAD+ carrier mutants. Moreover, in vivo measurement of ABA dynamics in seedlings of an ABA-specific optogenetic reporter - ABAleon2.1 treated with NAD+ showed increases in ABA content, suggesting that NAD+ impacts on stomatal development through ABA synthesis and signaling. The results demonstrate that intracellular NAD+ homeostasis is essential for normal stomatal development, and provide a link between central metabolism and developmental plasticity. Posteriorly, NAD+ carrier mutants were grown under elevated CO2 concentrations and overall results showed that, under high CO2 , the mutants displayed reductions in total biomass and leaf number compared to the control under ambient CO2 . Furthermore, higher levels of photorespiratory intermediates such as glutamate and glycine were found in the mutant lines under elevated CO2 . Moreover, mutant lines produced much less seeds than wild-type plants regardless of CO2 concentration, demonstrating that NAD+ compartmentalization is fundamental during reproductive phase in both ambient and high CO2 concentration. With the aim to deeper study NAD + dynamics, we transformed wild-type and a ndt1 mutant line with the Peredox-mCherry sensor that permits the measuring of cytosolic NADH dynamics in vivo. The cytosol of ndt1 mutant lines presented higher levels of NADH/NAD + compared to the control line. Additionally, increased cytosolic levels of NADH/NAD+ in leaves of ndt1 mutants was observed upon the exogenous feeding of sugars and tricarboxylic acid (TCA) cycle intermediates. Surprisingly, light, mitochondrial electron transport chain (mETC) inhibitors and oxygen deprivation treatment did not show significant differences in cytosolic NADH/NAD+ content in ndt1 mutants compared to wild-type. The results provide evidence of disruption of NAD+ balance among organelles in ndt1 mutants and show the power of this technique to follow NADH dynamics in vivo. Collectively, the data presented provide different inputs to show that, not only NAD+ metabolism, but also NAD+ distribution across organelles, are fundamental to drive essential biological processes in plants. Furthermore, this study proposes a direct link between central metabolism and early developmental process such as stomatal development. Keywords: Nicotinamide adenine dinucleotide. NAD+ transport. Metabolism. Development.Item Alterações físicas e bioquímicas em tubérculos de batata tratados com inibidores de brotação(Universidade Federal de Viçosa, 2020-03-05) Moreira, Karoliny Ferreira; Finger, Fernando Luiz; http://lattes.cnpq.br/2405520907557339A batata (Solanum tuberosum L.) é uma hortaliça que se destaca em âmbito mundial sendo que durante o armazenamentoapresenta acentuada brotação. Objetivou-se nesse trabalho definir quais os comportamentos do inibidor de brotação 1,4-dimetilnaftaleno (DMN) comparado ao isopropil N(3-clorofenil) carbamato (CIPC), em relação ao número, comprimento e incidência das brotações, enzimas do escurecimento enzimático e ao metabolismo de carboidratos. O delineamento experimental utilizado foi o inteiramente casualizado em esquema de parcela subdividida, sendo os tratamentos: o armazenamento constou do controle, da aplicação de 1,4-DMN (20 mg.kg -1 ) e do CIPC (30 mg.kg -1 ) com quatro repetições cada e com subparcelas compostas pelo tempo de armazenamento: 0, 15, 30, 45, 60, 75, 90 e 105 dias após a aplicação. As aplicaçções foram realizadas pelo processo de fumigação nos tubérculos durante o tempo decorrido de duas horas em ambiente fechado. A partir disso realizou-se as seguintes análises: perda de massa fresca acumulada; número e comprimento de brotos; atividade das enzimas peroxidase (POD) e polifenolxidase (PPO); compostos fenólicos; incidência de brotação; amido; açúcares solúveis totais, redutores e não redutores e coloração após fritura. Os tubérculos submetidos aos tratamentos com os inibidores DMN e CIPC apresentaram menor perda de massa, número e comprimento dos brotos, teor de açúcares redutores e maior teor de amido em relação ao tratamento controle, sendo assim, esses tubérculos continham características suficientes e necessárias para o processamento de fritura mantendo a qualidade final dos palitos pré-fritos. Palavras-chave: Solanum tuberosum L.. Brotação. Processamento.Item Deciphering the carbon starvation response in Arabidopsis thaliana: autophagy, alternative respiration and beyond(Universidade Federal de Viçosa, 2020-11-18) Barros, Jessica Aline Sousa; Araújo, Wagner Luiz; http://lattes.cnpq.br/8783435505580467Throughout their life, plants are constantly challenged with environmental changes that compromises carbohydrate production. Energy deprivation triggers massive reprogramming of transcription, which further supports cellular energetic homeostasis. Therefore, catabolic pathways are generally activated leading to the catabolism of protein, lipid, and chlorophyll. Although our current understanding of plant mechanisms to overcome low energy conditions has significantly enhanced, there are still many open questions to be addressed. This thesis is therefore largely focused on understanding (i) the importance of autophagy as a mechanism of lipids and chloroplast recycling; and (ii) the transcriptional regulation of respiratory alternative pathways during low energy stress. Compelling evidence demonstrated that autophagy and amino acid catabolism are important factors of plant response to energy deprivation. This fact aside, the importance of autophagy on the remobilization of lipid substrates to sustain energy production remains unclear. Thus, we first summarized and discussed novel findings demonstrating the multifaceted roles of autophagy in lipid metabolism. Next, we provided experimental evidence of autophagy requirement to ensure lipid homeostasis during energy starvation conditions. Our findings revealed that autophagy disruption affects proper membrane mobilization and activates a general chloroplast lipid degradation program while failing to produce cytosolic lipid droplets. The degradation of chloroplasts is a hallmark of natural and stress-induced senescence, and a key role of autophagy in this process has been demonstrated elsewhere. Notably, the marked degradation of chloroplast components in mutants with disruption of autophagy (atg mutants) reported by several previous studies, raised the question whether other pathways of chloroplast degradation may also have a role in the remobilization of chloroplast components. It has been previously reported that the chloroplast vesiculation (CV) pathway is highly induced in atg mutants contributing with their early senescence phenotype during energy starvation. Thus, in the second part of this thesis the importance of CV and its coordination with autophagy under extended darkness was investigated. By using CV RNAi lines it was demonstrated that CV pathway plays a relatively minor role on Arabidopsis starvation response. However, further characterization of double mutants for CV and autophagy pathways highlighted the requirement of CV for chloroplast remodeling of atg mutants under darkness. Within the last chapter novel insights concerning the regulatory components that modulates plant survival under low energetic conditions are shown. To this end, the WRKY45 transcription factor was identified as a potential regulator of metabolic reprogramming, by precisely adjusting amino acid and organic acid response via a possible regulation of mitochondrial stress signaling components. Collectively, the results obtained here describe novel mechanisms underlying plant responses to low energy conditions. These findings are discussed in the context of our current knowledge concerning energetic metabolism, autophagy, and senescence in plants. Keywords: Autophagy. Energetic stress. Lipids. Metabolism. Senescence.Item Caracterização fisiológica do transportador mitocondrial de adenilatos AtAAC1(Universidade Federal de Viçosa, 2020-10-30) Batista, Rita de Cássia Monteiro; Nesi, Adriano Nunes; http://lattes.cnpq.br/1026340785612230As células necessitam de energia para a manutenção de vários processos metabólicos. Adenosina trifosfato (ATP) é um metabólito central no metabolismo celular, participando de inúmeras transações energéticas, e assim considerado uma fonte de energia biológica universal em todos organismos vivos. Em tecidos heterotróficos a mitocôndria é a organela responsável pela maior parte do suprimento do ATP necessário para os processos metabólicos. Para sua utilização, os adenilatos (adenosina monofosfato, AMP; adenosina difosfofato, ADP; e ATP) são distribuídos entre os compartimentos celulares via proteínas carreadoras especializadas em transporte. Dentre essas proteínas se encontram os carreadores do tipo antiporte ADP/ATP (AACs), que exportam o ATP da matriz mitocondrial para o citosol e em troca importam o ADP do citosol. Em Arabidopsis thaliana são encontradas três isoformas de AACs (AAC1, AAC2 e AAC3). Entre essas isoformas, o AAC1 é a mais expressa em diferentes tecidos e estágios fenológicos. Contudo, a sua função fisiológica ainda não foi elucidada em plantas. Neste trabalho, avaliou-se o papel do transportador mitocondrial AAC1 em A. thaliana. Para tal, foram utilizadas uma linha mutante com inserção de T-DNA (KO) e quatro linhas antisenso sob o controle do promotor 35S (AS2, AS4, AS5 e AS7) com reduzida expressão de AAC1. Em folhas expandidas de plantas deficientes na expressão de AAC1, observou-se redução nastaxas de respiração noturna sem alterações em parâmetros de fotossíntese em relação a plantas selvagens. Adicionalmente, foram observados diminuição no número de folhas e na área foliar específica. Verificou-se também acúmulo de açucares (glicose, frutose, sacarose) e malato em folhas das plantas com baixa expressão de AAC1. Observou-se maiores teores de aminoácidos em paralelo com menores conteúdos de proteínas em folhas. Nas raízes, a deficiência na expressão de AAC1 resultou em menor crescimento, o qual foi associado a menores taxas respiratórios nos tecidos desse órgão. Em conjunto, os resultados apresentados sugerem que AAC1 desempenha um papel importante na respiração mitocondrial impactando o crescimento da planta como um todo, sem alterações marcantes na eficiência fotossintética. Palavras-chave: Translocador 1 do Nucleotídeo Adenina. Metabolismo. Respiração celular. Mitocôndrias. Células -Item Selenium uptake and the nutritional quality of rice (Oryza sativa L.) grains are affected by nitrogen availability(Universidade Federal de Viçosa, 2020-10-21) Teixeira, Lubia da Silva; Ribeiro, Dimas Mendes; http://lattes.cnpq.br/1610936721869054Selenium (Se) and nitrogen regulate primary metabolism in rice plants. However, information on how nitrogen availability affects Se uptake and accumulation in rice grains is hitherto lacking. Thus, the aim of the work was to evaluate how the combined effect of Se and nitrogen can affect the rice production and grain nutritional composition. Were observed no significant effect of Se on concentrations of pigments, A, gs, Ci/Ca and E regardless of nitrogen supply. Although Se had no effect on grain production, Se treatment combined with nitrogen treatment increased the expression of OsSULTR1.2 and OsPT2 in root more than nitrogen supplies alone, while the increase in OsNIP2.1 was regardless of nitrogen supply. However, the increase in nitrogen supply, improving the relative expression of OsNRT1.1B, a nitrate uptake transporter, enhancing the translocation of Se from the root to shoot of plants, improving the Se content in grains of rice. Our results also showed a significant increase in concentrations of N, P, S and Fe in grain of rice plants treated with Se grown in nitrogen-limiting conditions while the Ca concentration increased regardless of nitrogen supply. On the other hand, Se tended to reduce concentrations of Cu and Zn and increased concentration of Mg and Mo in grain of plants grown in 16 mM and 24 mM nitrogen compared with nitrogen-limited plants. Furthermore, there was a synergistic interaction between nitrogen and Se in the content of total proteins in the grains, since the proportion of the glutelin fraction was markedly elevated in the grains of Se-treated plants. In addition, Se led to a significant increase of total amino acid in grain of plants grown in nitrogen-limited condition and in 16 mM nitrogen when compared with plants grown at a comparable nitrogen supply. However, the effect of increased nitrogen concentration on the concentrations of soluble sugar and starch was independent of Se supplied. Therefore, the combination of Se plus nitrogen concentration had a positive effect on caloric levels of grain, but a negative effect on the concentration of a range of minerals (Fe, Zn, Cu and Mn). Keywords: Gene expression. Selenium fertilization. Rice yield. Nitrogen supply.Item Molecular and physiological insights into the role played by boron in the soybean- Phakopsora pachyrhizi interaction(Universidade Federal de Viçosa, 2020-07-20) Picanço, Bárbara Bezerra de Menezes; Rodrigues, Fabrício de Ávila; http://lattes.cnpq.br/5226110728919728Considering the potential of Asian Soybean Rust (ASR), caused by the fungus Phakopsora pachyrhizi, to reduce soybean yield, this study investigated the effect of boron (B) on soybean resistance against ASR. The photosynthetic performance (chlorophyll a fluorescence and concentration of photosynthetic pigments), the concentration of total soluble phenolics compounds (TSP) and lignin-thioglycolic acid (LTGA) derivatives as well as the expression of defense- and B-related genes were analyzed. The supply of B to plants grown hydroponically with nutrient solutions containing 0.25 or 1.0 mM B did not show reduction in ASR severity. Confirming this result, the expression of TEF1 gene (translation elongation factor 1α of P. pachyrhizi) increased regardless of B rates. Additionally, higher B foliar concentration occurred for inoculated plants supplied with 1.0 mM B. The photosynthetic process was impaired during the infection process of P. pachyrhizi regardless of B rates. The TSP concentration was significantly high at 15 dai for non-inoculated plants supplied with 1.0 mM B in contrast to non-inoculated plants receiving 0.25 mM B. The LTGA derivatives concentration was higher for inoculated plants regardless of B supply. Defense-related genes were up-regulated in inoculated plants, regardless of B supply. Genes encoding for nitrate and nitrite reductase were more expressed at ideal B rate at 10 and 15 dai, and at high B rate at 3 and 5 dai, for inoculated plants. Genes encoding for rhamnogalacturonan II were more expressed at ideal B rate at 15 dai, and at high B rate at 10 dai, for non-inoculated plants. There was no changes in the expression of the genes coding for phenylalanine ammonia-lyase (PAL2.1) as well as isochorismate synthase (ICS1 and ICS2) regardless of B rates and P. pachyrhizi infection. In conclusion, the supply of high B rate to soybean plants did not result in an increase in their resistance against ASR independently of B supply. Keywords: Asian soybean rust. Photosynthesis. Plant nutrition. Host defense responses.Item Physiological and hydraulic mechanisms of drought tolerance in plants : implications of CO2 and irradiance(Universidade Federal de Viçosa, 2020-02-17) Avila, Rodrigo Teixeira; DaMatta, Fabio Murilo; http://lattes.cnpq.br/6404622647636394Herein, it is present a series of experiments divided into four chapters with the purpose to immerse deep into some physiological and hydraulic responses to drought and also how some of them interact with environmental variability such as elevated [CO2] and irradiance. On the first two chapters it is presented drought responses of coffee plants, one of the most important commodities worldwide, under elevated (700 ppm) and ambient (400 ppm) [CO2] On the first chapter we found that drought-stressed 700-plants were able to keep hydraulic conductance for longer, transpiring more than 400-plants. Correlative evidence is shown that aquaporins may play major roles in these processes. In addition, Well-watered 700-plants displayed lower whole-plant transpiration rates than their 400- counterparts. This was not associated with maximum gs per se, but rather with an increased stomatal closure rate upon vapor pressure deficit transitions, which occur innumerous times over the course of the day. On the second chapter we found that elevated [CO2] improved carbon assimilation, water use-efficiency and biomass accumulation regardless watering, in addition to decreasing the oxidative pressure under drought conditions. Elevated [CO2] also promoted key allometric adjustments linked to drought tolerance, e.g. more biomass partitioning towards roots with a deeper root system. Improved growth under enhanced air [CO2] was unlikely to have been associated with global changes on hormonal pools but rather with shifts on carbon fluxes. Altogether, results from the chapters 1 and 2 suggest that [CO2] is perceived by the plant as a key environmental factor having profound implications on how plants respond to drought, thus permitting 700-plants to have an improved fitness under drought when compared to 400- plants. In the third and fourth chapters, efforts were focused on analyzing hydraulic aspects of several different species. O the third chapter, we focused on finding anatomical drivers related to inter- and intraspecific xylem embolism resistance. Vessel lumen fraction was the only anatomical trait measured that correlated with xylem embolism resistance across scales and species. Light was found to drive only minor differences in stem and not leaf embolism resistance. Our data suggest that conduits highly dispersed in a matrix of imperforate elements may be better protected against the spread of embolism than conduits that are packed in close proximity, which may contribute to our understanding of the mechanisms behind air-seeding. Finally at the fourth chapter, it is presented deep insights into the possible existence of a well-established water potential threshold beyond which vessels and tracheids will embolize We found that, in vessel-based xylem species, individual xylem conduits had a more well-defined water potential at which embolism occur, with considerable pre-existing embolism being able to influence the vulnerability of the xylem. In contrast, conduits in tracheid-based xylem did not display a well-defined individual water potential threshold at which embolism occurs and thus pre-existing embolism did not alter the vulnerability of xylem. Keywords: Elevated CO2. Drought. Coffee. Embolism, Xylem.