Papel da autofagia nas respostas à acidez e ao fotoperíodo em Arabidopsis thaliana
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2022-08-23
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Universidade Federal de Viçosa
Resumo
Devido à sua natureza séssil, as plantas são repetidamente submetidas a vários e distintos estresses ambientais. Tais estresses, ainda que moderados, são capazes de desencadear respostas prejudiciais ao crescimento vegetal causando perdas no rendimento produtivo. Em plantas submetidas a distintos estresses abióticos, a autofagia apresenta-se como um dos principais sistemas proteolíticos de atenuação dos danos. A autofagia é governada pelos denominados genes relacionados à autofagia (ATG), e está envolvida na degradação e reciclagem de constituintes citoplasmáticos, através de seu sequestro até o vacúolo. Neste trabalho, investigou- se como e em que extensão a autofagia participa das respostas (i) ao ambiente ácido e (ii) a flutuações no fotoperíodo. Para tanto, alterações fisiológicas e metabólicas ocasionadas pela deficiência do processo autofágico (mutantes atgs) em Arabidopsis thaliana submetidas a tais estresse foram avaliadas. Na primeira parte, observou-se que o gene ATG5 participa ativamente das repostas ao ambiente ácido e sua ausência culmina em danos oxidativos severos, quando comparado às plantas deficientes para o gene ATG7, que lidam de forma mais efetiva com o estresse ácido através do aumento da expressão da oxidase alternativa (AOX). Em conjunto, os resultados sugerem que o pH ácido do meio induz a senescência, principalmente em mutantes com deficiência do processo autofágico. Em síntese, a autofagia está aparentemente relacionada às respostas a condição ácida mediando a interrupção da senescência precoce. Na segunda parte deste trabalho, investigou-se como a autofagia participa na sincronização dos ritmos circadianos e sua relação com o metabolismo em resposta a flutuação no fotoperíodo (dias curtos e dias longos). De modo geral, a deficiência no processo autofágico levou à dessincronização do relógio circadiano, alterando o padrão de expressão de genes centrais envolvidos na regulação do ritmo circadiano em função da variação no fotoperíodo. Além disso, o fotoperíodo parece também coordenar a expressão de genes autofágicos, o que consequentemente ocasiona variações no metabolismo energético das plantas. Tomadas em conjunto, essas alterações metabólicas e moleculares culminam em maiores níveis de clorofila e maior fotossíntese em dias longos que se traduzem em maior crescimento e área foliar, quando comparado aos dias curtos. Assim, a autofagia é importante na sincronicidade do relógio em relação ao crescimento da parte aérea das plantas. Coletivamente, os resultados obtidos indicam a significância da autofagia nas respostas ao estresse ácido bem como na modulação e ajuste dos ritmos circadianos em plantas. Trabalhos futuros serão ainda necessários para esclarecer como e em que extensão essa aparente reprogramação metabólica e molecular modula as respostas vegetais à acidez do solo em condições de flutuação no fotoperíodo. Palavras-chave: Acidose; Fumarato; Regulação gênica; Ritmo circadiano; Senescência.
Due to their sessile nature, plants are repeatedly subjected to various and distinct environmental stresses. Such stresses, even if moderate, are capable to trigger deleterious responses to plant development, compromising yield. In plants subjected to different abiotic stresses, autophagy presents itself as one of the main proteolytic systems of damage attenuation. Autophagy is governed by the so-called autophagy- related genes (ATG) and is involved in the degradation and recycling of cytoplasmic constituents, through their sequestration to the vacuole. In this work, we investigated how and to what extent autophagy participates in responses (i) to an acidic environment and (ii) to fluctuations in photoperiod. To this end, physiological and metabolic changes caused by the deficiency of the autophagic process (atgs mutants) in Arabidopsis thaliana submitted to such stress were evaluated. In the first chapter, it was observed that the ATG5 gene actively participates in the responses to the acid environment, and its absence culminates in severe oxidative damage, when compared to plants deficient in the ATG7 gene, which deal more effectively with acid stress through increased alternative oxidase (AOX) expression. Taken together, the results suggest that acidic pH induces senescence, especially in mutants with a deficiency of the autophagic process. In summary, autophagy is apparently related to plant responses to an acid condition in the interruption of early senescence. In the second part of this work, we investigated how autophagy participates in the synchronization of circadian rhythms and its relationship with metabolism in response to photoperiod fluctuation (short days and long days). In general, the autophagy deficiency led to the desynchronization of the circadian clock, significantly altering the expression pattern of genes central involved in the regulation of the circadian rhythm in response to photoperiod variation. In addition, the photoperiod also seems to coordinate the expression of autophagic genes, which consequently causes variations in the energy metabolism of plants. Taken together, these metabolic and molecular changes culminate in higher chlorophyll levels and photosynthesis on long days that are translate into greater growth and leaf area compared to short days. Thus, autophagy is most likely important in clock synchronicity in relation to plant shoot growth and development. Collectively, our results indicate the significance of autophagy in acid stress responses as well and in the modulation and adjustment of circadian rhythms in plants. Future work is still required to clarify how and to what extent this apparent metabolic and molecular reprogramming modulates plant responses to soil acidity under photoperiod fluctuation conditions. Keywords: Acidosis. Circadian rhythm. Fumarate. Gene regulation. Senescence.
Due to their sessile nature, plants are repeatedly subjected to various and distinct environmental stresses. Such stresses, even if moderate, are capable to trigger deleterious responses to plant development, compromising yield. In plants subjected to different abiotic stresses, autophagy presents itself as one of the main proteolytic systems of damage attenuation. Autophagy is governed by the so-called autophagy- related genes (ATG) and is involved in the degradation and recycling of cytoplasmic constituents, through their sequestration to the vacuole. In this work, we investigated how and to what extent autophagy participates in responses (i) to an acidic environment and (ii) to fluctuations in photoperiod. To this end, physiological and metabolic changes caused by the deficiency of the autophagic process (atgs mutants) in Arabidopsis thaliana submitted to such stress were evaluated. In the first chapter, it was observed that the ATG5 gene actively participates in the responses to the acid environment, and its absence culminates in severe oxidative damage, when compared to plants deficient in the ATG7 gene, which deal more effectively with acid stress through increased alternative oxidase (AOX) expression. Taken together, the results suggest that acidic pH induces senescence, especially in mutants with a deficiency of the autophagic process. In summary, autophagy is apparently related to plant responses to an acid condition in the interruption of early senescence. In the second part of this work, we investigated how autophagy participates in the synchronization of circadian rhythms and its relationship with metabolism in response to photoperiod fluctuation (short days and long days). In general, the autophagy deficiency led to the desynchronization of the circadian clock, significantly altering the expression pattern of genes central involved in the regulation of the circadian rhythm in response to photoperiod variation. In addition, the photoperiod also seems to coordinate the expression of autophagic genes, which consequently causes variations in the energy metabolism of plants. Taken together, these metabolic and molecular changes culminate in higher chlorophyll levels and photosynthesis on long days that are translate into greater growth and leaf area compared to short days. Thus, autophagy is most likely important in clock synchronicity in relation to plant shoot growth and development. Collectively, our results indicate the significance of autophagy in acid stress responses as well and in the modulation and adjustment of circadian rhythms in plants. Future work is still required to clarify how and to what extent this apparent metabolic and molecular reprogramming modulates plant responses to soil acidity under photoperiod fluctuation conditions. Keywords: Acidosis. Circadian rhythm. Fumarate. Gene regulation. Senescence.
Descrição
Palavras-chave
Arabidopsis thaliana, Ácido fumárico, Regulação da expressão gênica, Ritmos circadianos, Senescência
Citação
GONÇALVES, Julia de Paiva. Papel da autofagia nas respostas à acidez e ao fotoperíodo em Arabidopsis thaliana. 2022. 73 f. Dissertação (Mestrado em Fisiologia Vegetal) - Universidade Federal de Viçosa, Viçosa. 2022.