Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Item Proteomic and metabolic impacts of the lack of 2-oxoglutarate dehydrogenase E1 subunit in Arabidopsis thaliana(Universidade Federal de Viçosa, 2022-04-29) Vargas, Jonas Rafael; Nesi, Adriano Nunes; http://lattes.cnpq.br/9028236058582130The enzyme 2-oxoglutarate dehydrogenase (2OGDH) is a tricarboxylic acid cycle enzyme. This enzyme is a multi-enzymatic complex formed by three subunits that together are responsible for catalyzing the conversion of 2-oxoglutarate (2OG) into succinyl-CoA with the release of NADH and CO 2 in the mitochondrial matrix. This enzyme is described as an important point of regulation and link between the metabolism of carbon and nitrogen since in its absence, important processes in the plant such as respiration, photosynthesis and nitrogen assimilation are altered. One way this enzyme exerts control over the metabolism is through the control in the levels of its substrate, 2OG, that is also used for the synthesis of amino acids in the chloroplast. In addition, 2OG plays a role in cell signaling and expression regulation through PII proteins and the 2-oxoglutarate-dependent dioxygenases. In order to help elucidate responses associated with the lack of specific subunits of 2OGDH complex, we set out to analyze the impact caused by the lack of the E1 subunit of the 2OGDH enzyme on the proteome of plants grown under control conditions and also approach the contributions of this enzyme in the response of plants to imposition and recovery of abiotic stress. As a result, we observed that the lack of the E1 subunit of the 2OGDH enzyme is related to a reduction in photosynthetic and photorespiratory metabolisms proteins that may explain the large growth reductions observed in the mutant plants. We also observed that during the period of stress and recovery, the lack of the E1 subunit has a greater impact on the metabolism of roots that respond more quickly to stress, where alternative pathways such as GABA shunt can be activated in order to overcome the lack of this enzyme, and during recovery carbon metabolism is prioritized over nitrogen in the roots. Keywords: 2-oxoglutarate dehydrogenase. Proteome. Abiotic stress. Respiration. ArabidopsisItem The Tick Tock of Biological Clocks on Crop Domestication and Plant Environmental Responses.(Universidade Federal de Viçosa, 2022-02-25) Siqueira, João Antonio Batista de; Araújo, Wagner L.; http://lattes.cnpq.br/4599642186886817Timing governs practically all processes documented, and thus since is extremely complex to alter temporal dynamics. Meanwhile, precise mechanisms to monitor the time are fundamental to ensure life on Earth. Organisms naturally develop differential abilities to monitor the time, wherein the biological chronometers regulate spatiotemporal dynamics, ensuring the emergence of new cells and allowing the organism can anticipate unfavorable environmental conditions. In this context, the biological clocks are highlighted due to their ability to timekeeping the circadian rhythms, development, and metabolism. This thesis is largely focused on the investigation of the functions of biological clocks in the context of plant growth and stress response as well as on investigating the functional role of the photoperiod to mediate aluminum (Al) tolerance. To this end, several complementary approaches were undertaken to understand: (i) the significance of biological clocks on crop domestication; (ii) the diel regulation of the Al tolerance in plants; and (iii) the specific behavior of root clock and its implication on plant yield. Firstly, it was demonstrated that tomato domestication apparently synchronized the distinct biological clocks of this species. Notably, the results demonstrate how this synchronization has contributed to the increased yield of cultivated tomatoes yet reduced their ability to tolerate abiotic stresses in comparison with wild tomatoes. In an attempt to demonstrate this, it was investigated the significance of water supply at different periods of the day in tomatoes. To this end, Solanum pennellii and S. lycopersicum (cv. M82) plants were exposed to different watering regimes: at dawn, dawn/dusk, and dusk. I was noted that the dusk watering treatment promoted a significant reduction in the number of leaves only in M82, whereas the other watering treatments did not alter the plant height in both genotypes. By analyzing the height and number of leaves in the different genotypes (MT, SFT ox , and SP5G pen ), it was observed an overall trend, revealing that dusk watering treatment resulted in smaller plants with fewer leaves than dawn and dawn/dusk watered plants. In conclusion, the analyses of the impacts from differentperiods of watering during the day suggested that watering tomatoes near dusk can significantly improve crop yield. Next, and mostly based on recent evidence, it was discussed that modifications of the DNA and metabolic checkpoints can mediate Al tolerance. Accordingly, mitochondrial organic acid metabolism and the genetic manipulation of DNA checkpoints were demonstrated to be not sufficient to promote plant survival under high Al concentrations. Compelling evidence showed that DNA checkpoint alterations are coupled with significant changes in mitochondrial metabolism. Thus, it was suggested that interactions between both mechanisms can occur in plants with elevated Al tolerance, supporting their growth even in soils with excessive Al levels. Following, it was demonstrated that photoperiod is closely associated with Al responses, wherein short-days (SD) favor the Al tolerance and long- days (LD) are related to Al sensitiveness. Genes involved in DNA checkpoints are induced specifically under LD conditions, arresting cell divisions and root elongation. Likewise, it was described how the photoperiodic regulation shapes Al tolerance in plants, which can contribute to developing a stable tolerance to Al in crops. Furthermore, the evidence suggested the occurrence of unique developmental phases for roots, in which these would be uncoupled from shoot phases. Altogether, it was indicated new frontiers to be pursued in plant biology, which have enormous potential to enhance nutrient use efficiency and reduce the use of chemical fertilizers in the next generation of crops. Keywords: Domestication. Biological clocks. Energetic stress. Metabolism.Item The antagonistic effect of AtCCR4a upon drought or heat stress conditions(Universidade Federal de Viçosa, 2021-08-27) Ponte, Lucas Roani; Reis, Pedro Augusto Braga dos; http://lattes.cnpq.br/9529336344331566Climate changes are expected to increase the severity of environmental adversities to plants, such as changes in rainfall regimes and the occurrence of more extreme temperatures, imposing a major risk to the productivity of agricultural crops. Throughout evolution, plants have evolved elegant mechanisms to cope with different adverse conditions, through the activation of different signaling pathways. The occurrence of abiotic stresses, such as osmotic stress or endoplasmic reticulum stress, tend to activate specific cellular pathways, such as the death cell signaling pathway mediated by proteins that contain DCD/NRP domains. The AtNRP1 and AtNRP2 proteins, components of the pathway in Arabidopsis, have been characterized as effectors of the programmed cell death process by the breakdown of the vacuolar membrane. Understanding how this pathway is integrated into cellular stability is essential, which justifies checking the predicted and not yet functionally characterized interactions among the components of the pathway with other proteins, such as AtCCR4a, a deadenylase that is both active in mRNA processing and in sucrose/starch metabolism. Given this context, we aimed to investigate the interaction between AtNRP2 and AtCCR4a, and its role during heat and drought stresses. We did not observe its direct involvement in the NRP-signaling pathway, however AtCCR4a was induced by osmotic and heat stresses. Furthermore, AtCCR4a disruption provides a drastically heat stress-sensitive phenotype, leading to reductions in photosynthetic pigment contents days after exposure to stress and negative changes in carbohydrate metabolism during this condition. Surprisingly, AtCCR4a disruption also promotes a more tolerant phenotype to water deficit, contributing to greater maintenance of relative water contents in leaf tissues and plant survival rate. These results indicate that AtCCR4a may have an antagonistic function in stress-responsive pathways, probably by regulating at a post-transcriptional level the expression of certain genes and/or by selecting specific target mRNAs. Keywords: Abiotic. Arabidopsis. Deadenylase. Heat. Water.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 Seed germination in response to salt stress and seed dormancy: On the roles of hormones and transcription factors(Universidade Federal de Viçosa, 2021-06-18) Silva, Nilo Cesar Queiroga; Ribeiro, Dimas Mendes; http://lattes.cnpq.br/8449292324218198The formation of a plant population depends on the plasticity of the germination of its seeds. This thesis aims to understand the mechanism of seed germination in response to salt stress and the role of transcription factors in germination. In chapter, it is reviewed the impact of climate change on seeds and the effect of hormonal balance in seeds. In addition, we present a brief review of the epigenetic effects on seeds and their impacts on plant adaptability, which can contribute to new perspectives. In the following chapters, we sought to investigate (i) the role of sodium and pH in hormonal balance during germination in Stylosanthes humilis. (ii) the role of transcription factors (TF) in dormancy and germination of Arabidopsis thaliana seeds. These studies were carried out in two independent experiments, which comprise chapters II and III presented here. In the second chapter, the following experiments were proceeded: seeds of S. humilis were incubated in a growth chamber. Ethylene, abscisic acid (ABA), 1-carboxylic acid-1-aminocyclopropane (ACC), ACC synthase (ACS) and ACC oxidase (ACO) and the primary metabolites were quantified. The results show that saline stress induces ABA synthesis independently of pH, leading to a reduction in the biosynthesis of ethylene, the main hormone involved in the germination of S. humilis. The third chapter aimed to understand how the transcription factor TEOSINTE BRANCHED1 CYCLOIDEA PROLIFERATING CELL FACTORS (TCP) family regulates the germination of Arabidopsis thaliana seeds. To help elucidate the functioning of the TCP8 and TCP14 genes, the TCP mutants were tested during seed germination. RNA- Sequencing data from seeds of TCP mutants were used to identify potential genes regulated by TCPs. The phenotype was evaluated and RT-qPCR (Real Time - quantitative PCR) were performed. In addition, transient gene expression analyses were performed on tobacco leaves. The results of this study show that TCP8 is a negative regulator of breaking dormancy in Arabidopsis thaliana. Together, these results suggest that TCP8 and TCP14 (both of class I TCPs) modulate the dormancy break in a contrasting manner. Thus, the role of TCP8 and TCP14 was demonstratedduring the germination of A. thaliana. Together, these data indicate the complexity of the germination process. Keywords: Germination. Dormancy. Seeds. Salt Stress. Stylosanthes humilis. Transcription factors. Arabidopsis thaliana.Item Photoperiod, salinity, and elicitors modulate the growth, morphophysiology, and biosynthesis of 20-hydroxyecdysone in Pfaffia glomerata (Spreng.) Pedersen(Universidade Federal de Viçosa, 2021-03-01) Fortini, Evandro Alexandre; Otoni, Wagner Campos; http://lattes.cnpq.br/8696085559149421Pfaffia glomerata is a plant widely used in traditional medicine, and a major producer of the secondary metabolite 20-hydroxyecdysone (20-E). Studies indicate that the biosynthesis of 20- E in P. glomerata can be regulated by abiotic stresses, but the mechanisms involved in this regulation are still unclear. Aiming to understand the physiological and molecular basis involved in the regulation of 20-E biosynthesis in P. glomerata, as affected by abiotic factors, ploidy level, and elicitation, three experiments were conducted. In the first experiment, plants of P. glomerata (accessions 22 and 43) were grown in vitro for 40 days under 4 different daily photoperiods: 4, 8, 16, and 24 h of light. We found that plants exhibited higher photosynthesis and biomass accumulation when grown in longer photoperiods. The plants also had anatomical and primary metabolism changes in response to the photoperiods tested, and the magnitude of these changes was accession-dependent. Furthermore, longer photoperiods promoted an increase in 20-E production, possibly as a result of higher carbon availability in the plants. In the second experiment, P. glomerata plants were grown in vitro and subjected to the following treatments: NaCl (50 mM), 5-azacytidine (5-azaC, 25 μM), and NaCl+5-azaC. After 40 days, we observed that the treatments promoted a significant reduction in growth and photosynthesis, as well as an increase in reactive oxygen species (ROS) and antioxidant enzyme production and an adjustment in primary metabolism. Through proteomic analyses, we identified differentially accumulated proteins mainly associated with the metabolism of carbohydrates, amino acids, and secondary metabolites, which may help us understand the salt stress and 5-azaC tolerance responses compared to control. Besides, we found that the 5-azaC and NaCl+5-azaC treatments reduced the accumulation of jasmonate biosynthesis-related protein, and this may contribute to reduced 20-E signaling and biosynthesis. In the third experiment, two different ploidies of P. glomerata (A22, diploid; and P28, a tetraploid derived from A22) were grown in vitro for 40 days, and the plants were elicited in the first 20 days with methyl jasmonate (methyl-JA) and methyl salicylate (methyl-SA). The elicitors induced contrasting anatomical modifications in P. glomerata leaves. Elicitation also reduced the photosynthetic rate of the plants, with a consequent change in primary metabolite content and reduction in growth. Treatments with methyl-JA and methyl-SA promoted oxidative stress, but also ROS mitigation by increasingantioxidant enzymes, and these changes were more significant in diploid plants. The production of 20-E was stimulated by elicitation with methyl-JA and was also higher in tetraploid plants. On the other hand, methyl-SA down-regulates Phantom gene expression, with a consequent reduction in 20-E biosynthesis. Taken together, our data provide important information on molecular, biochemical, and physiological mechanisms involved with the regulation of 20-E biosynthesis, as well as enable biotechnological strategies for increasing the production of this metabolite in P. glomerata plants grown in vitro. Keywords: Phytoecdysteroids. Abiotic stress. Photosynthesis. Medicinal plant. Proteomics. Phytohormones. Polyploidy.Item Desmonostoc salinum CCM-UFV059, a novel cyanobacteria from a saline- alkaline lake: molecular and physiological responses to light, desiccation and salt stress(Universidade Federal de Viçosa, 2019-02-22) Alvarenga, Luna Viggiano de; Araújo, Wagner Luiz; http://lattes.cnpq.br/5025552116262277Cyanobacteria are widespread photosynthetic prokaryotes and are among the oldest organisms on Earth. During their long evolution, cyanobacteria developed an enormous diversity in terms of morphology, metabolic plasticity and molecular properties, which seems to be important factors to cope with limiting environmental conditions and allowed their ecological success in almost all known photic ecosystems. The first part of this work consisted of the taxonomic characterization, using the polyphasic approach, of the strain Desmonostoc salinum CCM-UFV059, a filamentous heterocytous cyanobacterium isolated from a hypersaline lake. Taken together, our data allowed the description of a new species and the first strain of the Desmonostoc genus from a saline environment. The second part of this work aimed to decipher the main salt acclimation mechanisms present in Desmonostoc salinum CCM-UFV059, because most studies on cyanobacterial salt acclimation have been carried out on unicellular strains, which cannot fix N 2 . We performed a comparative study using the model strain Nostoc PCC7120, and we could observe a remarkable high salt tolerance displayed by Desmonostoc salinum CCM-UFV059. In cells of Desmonostoc salinum CCM-UFV059 the intracellular sodium content was significantly lower than in Nostoc PCC7120 and these cells were able to sustain photosynthetic activity up to 0.5 M NaCl while Nostoc PCC7120 cells were not. Moreover, Desmonostoc salinum CCM- UFV059 induced sucrose over-accumulation under desiccation stress conditions, which allowed this strain to survive harsh desiccation stress. Together with the presence of highly unsaturated lipids in the membrane, the high sucrose production and the intense export of sodium could explain, at least partially, how Desmonostoc salinum CCM-UFV059 is capable of acclimate to high salinities and to resist longer desiccation periods. Collectively, our results provide the first insights into the physiological adaptations explaining the remarkable high salt and desiccation tolerance presented by this strain. Furthermore, given that cyanobacteria have several biotechnological applications, such as the production of biomass for human and animal consumption, and metabolites of industrial interest, the third part of this work was performed to analyze the physiological and metabolic responses of Desmonostoc salinum CCM-UFV059 submitted to different light availabilities, aiming at finding the light regime suitable for maximal biomass production as well as to better understand how distinct growth conditions may interfere within the basal metabolism. Collectively our results indicate that Desmonostoc salinum CCM-UFV059 display a highly plastic metabolism and the ability to grow in a large range of light regimes, that open the possibility to outdoor cultivation and commercial use of this species that has a great biotechnological potential. Notwithstanding, further research is clearly required in order to enable a large scale cultivation of Desmonostoc salinum CCM-UFV059.