Variação intraespecífica, autofagia e autocitotoxicidade em canais secretores de Anacardium humile a. St.-hil. (Anacardiaceae)
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Data
2023-06-21
Autores
Carvalho, Shelly Favorito de
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Universidade Estadual Paulista (Unesp)
Resumo
Por meio da combinação de diversos métodos em botânica estrutural e biologia celular, neste estudo analisamos comparativamente os canais secretores no caule em sua porção aérea e subterrânea de Anacardium humile A. St-Hil. a fim de acessar variações intraindividuais relacionadas ao ambiente aéreo e subterrâneo; investigar a ocorrência de autofagia e seus tipos, bem como, a ocorrência de autocitotoxicidade e de mecanismos citoprotetores em células epiteliais secretoras de resina. Os resultados mostraram diferenças significativas na distribuição, histoquímica e ultraestrutura das células epiteliais dos canais secretores no caule em sua porção aérea e subterrânea. As células epiteliais dos canais na porção aérea, no pico da secreção, apresentaram formatos e tamanhos variáveis, com núcleo volumoso e citoplasma denso com ribossomos livres, polirribossomos, mitocôndrias com cristas desenvolvidas e plastídios elipsóides com inclusões elétron-opacas circundados por retículo periplastidial. Já na porção subterrânea, as células epiteliais no pico da secreção apresentaram formato e tamanho regulares, um grande vacúolo central, citoplasma reduzido a uma fina camada na periferia da célula e população reduzida de organelas. Dois mecanismos de autofagia foram detectados nas células epiteliais, sendo a macroautofagia encontrada em células ativas em secreção e a microautofagia em células em estágio final de secreção. As mudanças observadas na morfologia das células epiteliais durante o ciclo secretor tais como dilatação acentuada do retículo endoplasmático liso, degradação das cristas mitocondriais e a formação de corpos multilamelares na matriz mitocondrial são fortes indícios de autocitotoxicidade da secreção, enquanto que a presença de HSP70 (heat shock proteins) e o aparecimento de figuras típicas de processo autofágico (fagóforos, autofagossomos e vacúolos autofágicos) foram associadas com mecanismos citoprotetores em resposta aos danos causados pela presença de substâncias tóxicas. O padrão de danos celulares e respostas citotóxicas das células epiteliais dos canais secretores é comum a outras estruturas secretoras de terpenos. A combinação de métodos imunohistoquímicos com análises convencionais e ultracitoquímicas em microscopia eletrônica de transmissão foi eficiente para mostrar que nesta espécie o ambiente abaixo e acima do solo exerce certa influência na organização subcelular e no funcionamento dos canais secretores; que os canais secretores apresentam tipos distintos de autofagia durante o ciclo secretor; que os componentes da secreções terpênicas são tóxicas às próprias células que os produzem, as quais, em reposta aos danos desenvolvem mecanismos citoprotetores. Os resultados obtidos neste estudo incentivam a aplicação de diferentes técnicas de microscopia de luz e eletrônica, incluindo imunolocalização e citoquímica ultraestrutural na área da botânica estrutural e abrem novas perspectivas no estudo da célula secretora em espécies nativas.
Through the combination of several methods in structural botany and cell biology, in this study we comparatively analyze the secretory canals in the stem in its above- and belowground portions of Anacardium humile A. St-Hil. in order to access intra-individual variations related to the above- and belowground environment; to investigate the occurrence of autophagy and its types, as well as the occurrence of autocytotoxicity and cytoprotective changes in resin-secreting epithelial cells. The results of the differentiation in the distribution, histochemistry and ultrastructure of the epithelial cells of the secretory canals in the stem in its above- and belowground portion. The epithelial cells of the canals in the aboveground portion, at the peak of secretion, reached variable formats and patterns, with a voluminous nucleus and dense cytoplasm with free ribosomes, polyribosomes, mitochondria with developed cristae and ellipsoid plastids with electron-opaque inclusions surrounded by periplastid reticulum. In the belowground portion, the epithelial cells at the apex showed regular shape and size, a large central vacuole, cytoplasm reduced to a thin layer at the periphery of the cell, and suppression of organelles. Two mechanisms of autophagy were detected in epithelial cells, macroautophagy being found in active cells in secretion and microautophagy in cells in the final stage of secretion. The changes observed in the morphology of epithelial cells during the secretory cycle such as marked dilation of the smooth endoplasmic reticulum, degradation of mitochondrial crests and the formation of multilamellar bodies in the mitochondrial matrix are strong indications of autocytotoxicity of secretion, while the presence of HSP70 (heat shock proteins) and the appearance of typical figures of autophagic process (phagophores, autophagosomes and autophagic vacuoles) were associated with cytoprotective mechanisms in response to the damage caused by the presence of toxic substances. The pattern of cellular damage and cytotoxic responses of the epithelial cells of the secretory canals is common to other terpene-secreting structures. The combination of immunohistochemical methods with conventional and ultracytochemical analyses in transmission electron microscopy was efficient to show that in this species the environment below and above ground exerts a certain influence on the subcellular organization and functioning of the secretory canals; that secretory canals have distinct types of autophagy during the secretory cycle; that the components of terpene secretions are toxic to the very cells that produce them, which, in response to damage, develop cytoprotective mechanisms. The results obtained in this study encourage the application of different techniques of light and electron microscopy, including immunolocalization and ultrastructural cytochemistry in the area of structural botany and open new perspectives in the study of the secretory cell in native species.
Through the combination of several methods in structural botany and cell biology, in this study we comparatively analyze the secretory canals in the stem in its above- and belowground portions of Anacardium humile A. St-Hil. in order to access intra-individual variations related to the above- and belowground environment; to investigate the occurrence of autophagy and its types, as well as the occurrence of autocytotoxicity and cytoprotective changes in resin-secreting epithelial cells. The results of the differentiation in the distribution, histochemistry and ultrastructure of the epithelial cells of the secretory canals in the stem in its above- and belowground portion. The epithelial cells of the canals in the aboveground portion, at the peak of secretion, reached variable formats and patterns, with a voluminous nucleus and dense cytoplasm with free ribosomes, polyribosomes, mitochondria with developed cristae and ellipsoid plastids with electron-opaque inclusions surrounded by periplastid reticulum. In the belowground portion, the epithelial cells at the apex showed regular shape and size, a large central vacuole, cytoplasm reduced to a thin layer at the periphery of the cell, and suppression of organelles. Two mechanisms of autophagy were detected in epithelial cells, macroautophagy being found in active cells in secretion and microautophagy in cells in the final stage of secretion. The changes observed in the morphology of epithelial cells during the secretory cycle such as marked dilation of the smooth endoplasmic reticulum, degradation of mitochondrial crests and the formation of multilamellar bodies in the mitochondrial matrix are strong indications of autocytotoxicity of secretion, while the presence of HSP70 (heat shock proteins) and the appearance of typical figures of autophagic process (phagophores, autophagosomes and autophagic vacuoles) were associated with cytoprotective mechanisms in response to the damage caused by the presence of toxic substances. The pattern of cellular damage and cytotoxic responses of the epithelial cells of the secretory canals is common to other terpene-secreting structures. The combination of immunohistochemical methods with conventional and ultracytochemical analyses in transmission electron microscopy was efficient to show that in this species the environment below and above ground exerts a certain influence on the subcellular organization and functioning of the secretory canals; that secretory canals have distinct types of autophagy during the secretory cycle; that the components of terpene secretions are toxic to the very cells that produce them, which, in response to damage, develop cytoprotective mechanisms. The results obtained in this study encourage the application of different techniques of light and electron microscopy, including immunolocalization and ultrastructural cytochemistry in the area of structural botany and open new perspectives in the study of the secretory cell in native species.
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Palavras-chave
Anacardium humile, Autofagia, Canais secretores, Citotoxicidade, Variação interindividual, Células epiteliais, Botânica, Interindividual variation, Secretory canals, Anacardiaceae, Autophagy, Cytotoxicity