Análise comparativa dos efeitos da microgravidade, calor e hipóxia no padrão de expressão gênica das plantas: uma abordagem bioinformática

Abstract

Plants are subjected to daily environmental changes and must respond optimally to tolerate these modifications. Alterations in gravity, hypoxia, and heat are examples of environmental changes that can induce abiotic stress, primarily triggering oxidative signaling. Since microgravity is not a condition naturally occurring on Earth, some exposure methods are required to place plants in environments with gravity approaching zero. The use of international space stations and space flights are ways to expose plants to this type of environment. However, there is still no consensus on all the effects that microgravity may trigger. Thus, comparing microgravity studies with other environmental factors can enhance understanding of plant responses to microgravity. In this context, the integration of transcriptomic data from studies available on open-access platforms was performed, investigating the impacts of microgravity, hypoxia, and thermal stress on plants. Since these environmental conditions may share oxidative signaling pathways, the objective of this integration was to enrich the understanding of plant responses to microgravity, heat, and hypoxia in a comparative manner, as well as to explore the differential and correlated effects of microgravity in international space station and space flight settings. Therefore, bioinformatics tools were employed to identify significantly activated central genes, ontologies, and metabolic pathways. For data integration, a selection was made according to inclusion and exclusion criteria. For example, studies should clearly state experimental conditions and compare stressed and non-stressed plants. Consequently, 16 microgravity studies were selected, including 11 from international space stations and 6 from space flights, along with 10 thermal stress studies and 9 hypoxia studies. This integration revealed significant regulation of genes related to chlorophyll biosynthesis. These results suggest that photooxidation may be an important effect under microgravity, hypoxia, and heat conditions. This effect appears to be independent of microgravity exposure type. There was also an overlap in the activation of antioxidant metabolic pathways: glutathione metabolism and phenylpropanoid biosynthesis, demonstrating that plants employ redox homeostasis pathways using different strategies. Primary metabolism, specifically through the production of sugars such as starch and fructose, is significantly affected under hypoxia, heat, and microgravity conditions. These sugars are essential for energy production, carbon metabolism, and gravity signaling. Therefore, oxidative signaling triggered by microgravity, heat, and hypoxia significantly affected chlorophyll production and primary metabolism; however, this impact may be mitigated by intense antioxidant activity. Comparing these responses to those induced by other environmental stresses provides important insights into the adaptive capacity of plants in environments with different gravitational forces. Such understanding is crucial for developing strategies to enhance crop resilience in terrestrial and space agriculture contexts.