Abordagens de Bioinformática aplicadas na análise de dados gerados por estresse abiótico em cana-de-açúcar: microgravidade e peróxido de hidrogênio

Abstract

Sugarcane (Saccharum spp.) is a C4 monocotyledonous plant adapted to tropical and subtropical environments belonging to the Poaceae family. Brazil stands out as the world's largest producer of this crop, playing a crucial role in the global sugarcane industry. Plants, including sugarcane, are susceptible to a variety of biotic and abiotic factors that can induce an oxidative stress. This stress results from an imbalance in the homeostasis between the production and degradation of Reactive Oxygen Species (ROS). This scenario can affect plant development and consequently yield. Among these ROS, hydrogen peroxide (H2O2) acts as a key signaling molecule, responding to various cellular stimuli in plant systems. The aim of this study was to identify, in the roots and leaves of sugarcane, the transcripts and genes that act in response to oxidative stress induced by microgravity and H2O2 at different concentrations, correlating the responses of different stressors, as well as their similarities, specific adaptations, and tolerance to oxidative stress. To achieve this, this thesis was structured into two distinct chapters. The first chapter employs bioinformatics tools to investigate the effects of altered gravitational fields as a stressor in sugarcane plants, with specific focus on responses to oxidative stress. This investigation is based on messenger RNA sequencing data analysis. The second chapter addresses the analysis of genes and proteins expressed by the induction of oxidative stress through the exogenous application of varied concentrations of H2O2 (0 mM, 10 mM, 20 mM, and 30 mM) over a period of 8 hours in sugarcane plants, considering that H2O2 is a signaling molecule of oxidative stress. This investigation was based on proteomic data analysis. In both approaches described in the chapters, Sorghum bicolor, Zea mays, and Oryza sativa subsp. japonica species were used as reference models. The results of bioinformatics analysis identified specific genes that act in response to microgravity, such as C5WVD4 associated with isoleucine synthesis and C5YLK6 in NADPH production. Additionally, genes with altered expression at different H2O2 concentrations were identified. For instance, C5XFH6 and B4G143, related to NADPH supply and positive regulation of ROS in photosynthesis, respectively, were among the genes with significant expression changes. Furthermore, the study identified enriched metabolic pathways in response to microgravity and H2O2. These pathways include selenium compound metabolism, photosynthesis-antenna proteins, and the pentose phosphate pathway, highlighting significant biochemical adaptations in sugarcane under the studied conditions. This multidisciplinary study, encompassing histology, biochemistry, RNA-seq analysis, and proteomics, provides a comprehensive understanding of the effects of microgravity and H2O2 on sugarcane. These changes were verified in tissue structural organization, lignin accumbased by bioinformatic analyses in identifying distinct genes/proteins uniquely expressed in each tissue and the activated metabolic pathways in leaves and roots. It elucidates the varied responses of sugarcane plants to altered gravity conditions during the VSB-30 sounding rocket flight and exposure to different H2O2 concentrations. The study reveals a complex network of genes and metabolic pathways activated in response to oxidative stress, playing a fundamental role in triggering defense and tolerance mechanisms. The generated data significantly enhance our understanding of plant responses to the analyzed adverse conditions, highlighting specific adaptive strategies employed. Additionally, the findings underscore the critical role of H2O2 in adaptive and survival responses, as well as the versatility of the phytohormone abscisic acid (ABA) in mediating signaling between roots and leaves. These insights are important for the development of genetic improvement strategies and optimization of cultivation practices to enhance plant performance under variable environmental conditions.