Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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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 Nickel and glyphosate on the potentiation of the soybean resistance against infection by Phakopsora pachyrhizi(Universidade Federal de Viçosa, 2020-03-18) Einhardt, Andersom Milech; Rodrigues, Fabrício de Ávila; http://lattes.cnpq.br/8666942935119852In this study, the effects of nickel (Ni) (60 g ha -1 Ni) and glyphosate (Gl) (960 g ha -1 e.a. Gl) spray on the antioxidative, defense, and ethylene metabolisms of soybean plants inoculated with P. pachyrhizi were evaluated. In the first experiment, the severity of Asian soybean rust (ASR) decreased by 35% in plants of cv. TMG 135 treated with Ni (+Ni). The malondialdehyde (MDA) concentration was higher in plants not treated with Ni (-Ni) than in +Ni plants and was linked to ASR severity and extensive colonization of the palisade and spongy parenchyma cells by fungal hyphae. The lignin concentration, β-1,3-glucanase (GLU) activity, and expression of the URE gene and the defense-related genes PAL1.1, PAL2.1, CHI1B1, and PR-1A were up- regulated in +Ni infected plants. Taken together, the information provided in this study showed the great potential of Ni to increase the basal level of soybean resistance to ASR and to complement other control methods within the context of sustainable agriculture. In the second experiment, ASR severity in plants of cv. TMG 135 decreased by 34% due to Ni supply. In inoculated plants, the MDA concentration and superoxide (O2-) and hydrogen peroxide (H2O2) accumulation were lower for +Ni plants in comparison to -Ni plants. The antioxidant enzymes activities were inefficient to avoid the high reactive species of oxygen (ROS) accumulation on -Ni inoculated plants. The photosynthetic pigments, maximum photochemical efficiency of photosystem II (PSII), effective yield of PSII, electron transport rate, rate of net carbon assimilation, stomatal conductance to water vapor, and transpiration rate values were higher and the yield for other non-regulated losses and internal CO2 concentration values were lower for +Ni inoculated plants in comparison to -Ni inoculated plants. High ROS production and the great damage to the photosynthetic apparatus damage caused by P. pachyrhizi infection on -Ni plants affected the synthesis of the sugars and increased the energetic consumption limiting therefore, the plant energetic reserves faster in contrast to +Ni plants. In conclusion, the cellular oxidative damage and the impairment on the photosynthetic apparatus of soybean plants caused by P. pachyrhizi infection were alleviated by supplying Ni foliarly. In the thirst experiment, ASR severity was lower by 37, 68, and 77% in plants of cv. TMG 132 supplied with Ni, Gl, and Ni and Gl (Ni+Gl) in comparison to plants supplied with water (control). The inoculation caused largest and fastest increase in the concentration of ROS and MDA in control plants in comparison to Ni and Gl plants. In inoculated plants, the Ni and Gl increased phenylalanine ammonia lyase and GLU activities and phenolics concentration. Additionally, Ni-treated plants showed a fasted cell wall lignification than control plants. Polyphenoloxidase activity was increased by Gl at 5 days after inoculation, regardless of P. pachyrhizi infection. In conclusion, this study demonstrated that Ni and Gl regulate differently the activity of defense enzymes and did not affect the antioxidant enzymes in soybean plants infected by P. pachyrhizi. In the fourth experiment, the ASR severity was reduced on plants of cv. TMG 132 sprayed with Ni and Gl. Carotenoids and chlorophylls concentrations were preserved for Ni, Gl, and Ni+Gl inoculated plants in comparison to that in control plants. Parameters of chlorophyll a fluorescence revealed photosynthetic apparatus damage and lowest destination of energy to photochemistry process on inoculated plants from the control treatment. Limitations on the photosynthetic machinery capacity of inoculated plants to capture light and use the absorbed energy by PSII reflected on their capacity to reduce the CO2 as indicated by the high values for internal CO2 concentration and low values for rate of net carbon assimilation. Low sugars concentration on inoculated plants from the control treatment was linked to their reduced photosynthetic capacity due to the high ASR severity. For non-inoculated plants, ethylene concentration was not affected by Ni and Gl, but its concentration decreased for inoculated plants being more pronounced for plants from the control treatment. In conclusion, this study sheds light into the role played by both Ni and Gl on ASR control from a physiological point of view. Soybean plants exposed to Ni and Gl were able to maintain their photosynthetic capacity and the great ethylene concentration during the infection process of P. pachyrhizi. Keywords: Plant nutrition. Herbicide. Host defense. Photosynthesis. Asian Soybean Rust.Item 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 Cloning and functional characterization of the OBSCURAVENOSA gene in tomato (Solanum lycopersicum L.)(Universidade Federal de Viçosa, 2020-12-22) Moreira, Juliene dos Reis; Zsögön, Agustin; http://lattes.cnpq.br/7790254421084872Heterobaric and homobaric leaves are found in many plant families and have a remarkable distribution in nature. What differentiates these two types of leaves is the presence or absence of bundle sheath extensions (BSEs), a structural trait which produces different physiological responses. Leaves with BSEs (heterobaric) have greater hydraulic integration and greater photosynthetic performance, on the other hand, leaves without BSEs (homobaric) have uniform photosynthesis along the blade and probably an improved mechanism to control water loss under stress conditions. Tomatoes currently cultivated were selected after long years of crop breeding. Originally, tomato is a heterobaric crop, however, most field cultivars have a spontaneous recessive mutation known as obscuravenosa (obv) and, as a consequence, have lost the BSEs. For several years, this mutation was unconsciously selected in conjunction with other traits of agronomic interest. This suggests that the variation between homobaric and heterobaric characters has agronomic value in tomato. The first step to better understand the impacts of BSE at the plant level and to be able to manipulate it within the tomato crop and in other crops is knowing the genes involved in its formation. For this, we use tomato as a model to elucidate the molecular bases that control the development of BSEs. Using publicly available resources combined with in silico analysis, we identified a strong candidate gene for the obv mutation. Solyc05g054030 has a SNP (A→G) in the third exon, which leads to the exchange of a histidine residue for arginine at position 135 of the protein. The gene encodes a zinc finger transcription factor C2H2 type. We have shown through predictions that the OBV protein has three classic zinc finger domains, which allow interaction with DNA. In the obv mutant, the exchange of histidine for arginine caused the loss of a zinc finger motif, which may have led to the interruption of the protein functionality. We complemented the obv mutant with the functional OBV allele recovering the clear vein phenotype . OBV further regulates the leaf insertion angle, leaf serration, vein density and fruit shape. OBV appears to coordinate the development of BSEs through an auxin-mediated mechanism, specifically by changes in some members involved in auxin signaling (ARFs and Aux/IAAs). We have identified a link between OBV and AUXIN RESPONSE FACTOR 4 (ARF4). The findings reported here will give support for identification of other components linked to the molecular pathway that directs the formation of BSEs in leaves. Keywords: Bundle Sheath Extension. Heterobaric leaf. Molecular cloning. Auxin.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 Metabolic and physiological aspects associated with differential aluminum tolerance in maize(Universidade Federal de Viçosa, 2020-02-18) Silva, Marcelle Ferreira; Araújo, Wagner Luiz; http://lattes.cnpq.br/1429418814649373Maize (Zea mays) is a major crop cultivated worldwide with several uses including animal feeding human consumption and alcohol production. Notably, it is mostly cultivated in tropical and subtropical regions, where acid soils are prevalent. In those acidic soils, the toxicity triggered by aluminum (Al), in special Al 3+ , is the main factor limiting agricultural production. In this context, strategies aiming at developing stress-resistant crops could increase productive capacity and reduce yield penalty. Al tolerance in maize has been associated with organic acid (OA) exudation, mediated mainly by the membrane transporter family MATE (MULTIDRUG AND TOXIC COMPOUND EXTRUSION). Which are responsible for citrate exudation to rizosphere in an OA/H + antiport in root cells in response to Al toxicity. In this study, we used five genotypes derived from Al-intermediate tolerant (L3) and Al-sensitive (L53) genotypes with differential expression of the gene MATE that culminated with differential Al tolerance. Given that OA is intimately related with tricarboxilic acid cycle the metabolic consequences of this differential Al-tolerance were investigated. Higher Al content was observed in Al treated samples in all genotypes comparing with its respective controls. Interestingly, Al treated seedlings of tolerant genotypes showed higher increase in Al content than seedling of sensitive ones. This fact aside, higher accumulation of Al was observed in roots of genotypes with lower OA exudation. Moreover, this change in Al uptake and transport also lead to significant changes in mineral elements content including calcium and magnesium. Histochemical evaluation of hydrogen peroxide (H 2 O 2 ) and superoxide (O 2- ) in roots indicate that accumulation of those reactive oxygen species was actually higher in absence of Al and that it was similar in presence of Al for tolerant genotypes, suggesting that cell division was less affected in those genotypes. Al tolerant genotypes were characterized by minor disturbances in primary metabolism (i.e. photosynthesis and respiration) while the sensitive genotypes, with little if any OA exudation, were characterized by Al-damage effects (i.e. root and shoot growth) since the first hours of Al exposure. Although our findings indicate that different organs of the same species can present distinct Al resistance and/or tolerance mechanisms they were collectively able to provide a better understanding of the mechanisms used by maize genotypes to avoid or to minimize Al toxicity. Keywords: Citrate exudation. Abiotic stress. Root growth. ZmMATE1Item ZAR1: um modulador negativo da resposta aos estresses por deficiência hídrica e do retículo endoplasmático(Universidade Federal de Viçosa, 2020-02-17) Fagundes, Débora Pellanda; Reis, Pedro Augusto Braga dos; http://lattes.cnpq.br/0872098826327622Estresses bióticos e abióticos são os principais desafios na agricultura e estudos de vias de sinalização são importantes para contornar essa problemática. A via de sinalização de morte celular programada (PCD) media por NRP/DCDs se destaca pela integração da resposta molecular de diversos estresses bióticos e abióticos culminando na morte celular programada. Esta via é modulada negativamente pela chaperona molecular BiP por mecanismos ainda não elucidados. A superexpressão da chaperona molecular BiP permite uma maior tolerância a condições de estresses osmótico e do retículo endoplasmático (RE) sob condições de deficiência hídrica. Em busca de genes envolvidos no mecanismo de tolerância mediado por BiP e seu efeito na via PCD mediada por NRP/DCDs, um escrutínio genético em plantas superexpressando BiP mutagenisadas foi realizado. Foram selecionadas plantas mutantes que suprimiam o fenótipo de tolerância a seca mediado pelo chaperone molecular BiP. Estas linhagens tiveram o genoma sequenciado e a identificação de mutações especificas permitiu a identificação de alguns genes candidatos. Assim ZAR1 (Zygotic Arrest 1), gene que codifica um receptor do tipo cinase (RLK) foi selecionado como gene candidato a supressor do mecanismo mediado por BiP. O presente trabalho realizou experimentos para tentar caracterizar o papel molecular e fisiológico de ZAR1. Foram geradas plantas superexpressando ZAR1 e plantas que tinham o gene de zar1 silenciado. Nos experimentos realizados foi demonstrado que o nível de expressão de ZAR1 altera o fenótipo de plantas de Arabidopsis thaliana, em condições de estresse no RE e estresse por deficiência hídrica. Sob deficiência hídrica plantas silenciadas para o gene zar1 apresentaram um fenótipo mais sensível a deficiência hídrica, comparado com plantas Col0, enquanto plantas superexpressando ZAR1 apresentaram um fenótipo mais tolerante que a Col0. Além disso, plantas superexpressando ZAR1 possuem um atraso do processo de morte celular induzida por um agente causador de estresse no RE (tunicamicina), enquanto plantas silenciadas apresentaram o processo de morte celular acelerado comparado com plantas controle. Através de ensaios de fosforilação in vivo foi demonstrado que ZAR1 é fosforilada em resíduos de serina e tirosina em condições de estresse no RE ou estresse osmótico. No entanto, não foi possível identificar quais os resíduos específicos de aminoácidos são os alvos de modificações pós-traducionais nestas condições. Embora se saiba que há interação entre ZAR1 e RGS1 (Regulador da Sinalização de Proteína G), a fosforilação de ZAR1 sobre RGS1 não havia sido identificada. Assim, um ensaio de fosforilação in vitro também foi realizado e demonstrou que ZAR1 pode fosforilar RGS1 em resíduos de serina ainda não caracterizados. Coletivamente, os resultados indicam que ZAR1 pode estar envolvido com a via de tolerância ao estresse por déficit hídrico e no RE ao atenuar da morte celular ativada por estresses. Além disso, ZAR1 pode atuar como um modulador da via de proteínas G heterotriméricas através da interação/modulação de RGS1, apresentando um papel-chave na resposta de estresse abiótico. Palavras-chave: RLK. Resposta a Estresse. Sinalização Celular.Item Creation of new model system for genetics in Capsicum sp(Universidade Federal de Viçosa, 2020-12-21) Naves, Emmanuel Rezende; Zsögön, Agustin; http://lattes.cnpq.br/1819675032688464Capsicum is a genus appreciated for its pungency, which favored the interaction with man and thus domestication. However, through crosses, pungency was removed in modern cultivars and fruit size and productivity were increased, the result of which is what we know as bell peppers. In Capsicum there are gaps in knowledge about phenomena related to hybridization such as heterosis, used to obtain highly productive varieties. This motivated us to perform intra and interspecific crosses with commercial cultivars of C. annuum and C. chinense to determine the extent of the phenomenon of heterosis. Intraspecific hybridization proved to be efficient in maintaining and even improving productive characteristics, while interspecific hybridization promoted extreme vegetative development to the detriment of the reproductive one. In addition, it was observed that reciprocity, compatibility and germination were dependent on the direction in which the crosses were made and the genotypes involved, as well as the influence of the pollen source on the fruit set, size and biometry of fruits. Capsicum fruits are not climacteric, which positions the genus favourably to create a new model system for genetics and physiology. The search for a productive cultivar, with small size and easy cultural management that can be tailored to laboratory work would represent a valuable first step. With this aim in mind, we scanned a germplasm bank for cultivars, mainly of C. annuum, with small size, fast cycle, prolificity and productivity with the task of representing in a reliable way, but in miniature, the productive and genetic potential of Capsicum found in commercial cultivars. After an initial screening of 14 Capsicum cultivars as candidates for the model plant, we found two cultivars of C. annuum here named 75 and CVO. These two cultivars were precocious in the cycle until anthesis and until the first ripe fruit, with compact size and more than adequate prolificacy. In addition, growth and reproduction were not compromised when grown under conditions of high density and root volume limitation, showing that they are able to grow in small spaces and containers, tofacilitate large-scale phenotyping and thus genetic studies. Thus, we found two cultivars suitable to represent in miniature the genetic potential of C. annuum, to allow and facilitate the advancement of genetic studies, and in addition with characteristics inherent and exclusive to the genus Capsicum such as pungency. This new model could represent a valuable contribution to the genetics of non-climacteric fruit ripening and fruit metabolism. Keywords: Plant model. Chili pepper. Hybridization. Heterosis. Yield. Plant growth.Item Relações coordenadas entre ciclo TCA e ciclo celular em células específicas em resposta ao alumínio em Arabidopsis thaliana(Universidade Federal de Viçosa, 2020-11-06) Silva, Welder Alves da; Araújo, Wagner Luiz; http://lattes.cnpq.br/8820367890261822A maioria dos estudos demonstrando os mecanismos pelos quais as plantas resistem à presença do alumínio (Al) estão associados à contribuição de ácidos orgânicos (AOs). Com efeito, pouco ou nada parece ter sido explorado acerca de como células radiculares específicas modulam sua expressão gênica para lidar com tal condição. Não obstante, trabalhos anteriores revelam que, na presença de Al, uma resposta central é a reprogramação do ciclo dos ácidos tricarboxílicos (ciclo TCA). Ademais, agentes genotóxicos, incluindo o Al, induzem pausas no ciclo celular para que as células tenham tempo para reparar o DNA danificado e não transmiti-lo às células- filha. No entanto, pouco ou nada se sabe acerca de como o Al conecta o reparo do DNA ao metabolismo mitocondrial, bem como e em que extensão essa conexão impacta nas divisões celulares na presença do Al. Portanto, o presente estudo avaliou aspectos chaves dos ciclos TCA e celular em Arabidopsis thaliana, em um nível pós-transcricional e célula-específico de expressão gênica, responsáveis por conferir resistência ao Al. Buscou-se, também, investigar se o perfil de metabólitos na raiz inteira está mais intimamente correlacionado às análises de expressão gênica observadas nas células corticais, comprometidas com a proteção do órgão, ou nas células do centro quiescente, comprometidas com a sobrevivência e a manutenção da identidade das demais células. Para tanto, foram utilizadas plantas de Arabidopsis thaliana expressando a construção p:GFP-FLAG-RPL18, e com promotores individuais (i) Cauliflower mosaic virus 35S (p35S:FLAG-RPL18), quase constitutivo; (ii) plastid endopeptidase (pPEP:FLAG-RPL18), específico do córtex radicular das zonas de alongamento e maturação; e (iii) SCARECROW (pSCR:FLAG-RPL18), específico do centro quiescente e endoderme radicular. Os resultados ora obtidos apontam que, nas linhas transgênicas p35S e pSCR, a presença de Al alterou a expressão de genes envolvidos com o ciclo celular, ao passo que foram verificadas alterações na expressão de genes envolvidos com o ciclo TCA em todas as linhas, especialmente na pPEP. Tais resultados estão em consonância com as mudanças verificadas nas três linhas no que tange ao perfil de metabólitos, destacadamente o de AOs. Em adição, ao se investigar o translatoma de células com identidades distintas, foi possível observar que: (i) a expressão gênica é, aparentemente, regulada diferencialmente de acordo com essa identidade (status de diferenciação celular, função celular, etc.) e (ii) a expressão gênica célula-específica,particularmente em células indiferenciadas (centro quiescente e endoderme) e diferenciadas (zona cortical das regiões de alongamento e maturação) explica, em larga extensão, como plantas de Arabidopsis respondem à presença de Al mediante uma reprogramação da expressão gênica em grupos específicos de células radiculares. Tomados em conjunto, estes resultados sugerem uma alta plasticidade, a nível metabólico e de expressão gênica célula-especifica, como importante componente das respostas ao Al em Arabidopsis thaliana. Palavras-chave: Alumínio. Translatoma. Célula-específico. Ciclo TCA. Ciclo celular.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.
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