Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
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 Molecular and metabolic responses associated with the lack of autophagy following energy deprivation in Arabidopsis thaliana(Universidade Federal de Viçosa, 2016-07-18) Barros, Jessica Aline Sousa; Araújo, Wagner Luiz; http://lattes.cnpq.br/8783435505580467The oxidation of carbohydrate in mitochondria is the primary energy source for cellular metabolism. However, during energy-limited conditions alternative substrates are required to support respiration. The oxidation of amino acids plays a key role in this process by generating electrons that can be transferred to mitochondrial electron transport chain via the electron transfer flavoprotein/ ubiquinone oxireductase (ETF/ETFQO) system. Compelling evidence has demonstrated the close association of autophagy in providing alternative substrates for power generation under carbohydrate-limited conditions; however, how and to which extent autophagy and primary metabolism interact to support respiration remains unclear. To obtain a comprehensive picture of the metabolic importance of autophagy during development and extended darkness Arabidopsis thaliana mutants with impairments in autophagy were used. atg mutants showed reduction of growth and seed production. Following extended darkness atg mutants were characterized by early signs of senescence as well as decreased chlorophyll content and maximum photochemical efficiency of PSII (Fv/Fm). Metabolite profile of dark-treated leaves revealed an extensive metabolic reprogramming in which increases in amino acids contents were partially compromised and thus limiting their utilization as substrate to sustain respiration in atg mutants. Additionally, transcript levels of genes involved in alternative pathways of respiration, amino acid catabolism, and chloroplast vesiculation (CV) were up-regulated in atg mutants. Our results thus suggest that autophagy contributes to energy availability by supplying amino acids for alternative pathways of respiration. Furthermore, our finding demonstrated the potential role of CV as a compensatory protein degradation pathway under C-limiting conditions when autophagy is impaired .