Banca de DEFESA: LUCAS FELIPE DA SILVA

BIOINFORMATICS APPROACHES APPLIED IN THE ANALYSIS OF DATA GENERATED BY ABIOTIC STRESS: MICROGRAVITY AND BY HYDROGEN PEROXIDE IN SUGARCANE PLANTS

VSB-30 sounding rocket, gravity force change, RNA-seq, oxidative stress, transcriptomics, proteomics, enrichment, metabolic pathways, Saccharum spp.

Sugarcane (Saccharum spp.) is a monocotyledonous plant of the Poaceae family, a C4 plant adapted to tropical and subtropical environmental. And Brazil is the world's largest producer. Plants can be subject to various biotic and abiotic factors that may induce oxidative stress. This stress is associated with an imbalance in the homeostasis between the production and degradation of Reactive Oxygen Species (ROS), conditions that can affect their development. Hydrogen peroxide (H2O2) acts as a signaling molecule in response to various cellular stimuli in plants. Therefore, this thesis was divided into two chapters. In the first chapter, bioinformatics tools were used to understand how changes in the gravitational field can trigger responses like oxidative stress in sugarcane plants, based on messenger RNA sequencing data. In the second chapter, oxidative stress was induced by exogenous application of H2O2 (0 mM, 10 mM, 20 mM, and 30 mM) for 8 hours at a temperature of 25-27 °C in sugarcane plants. Bioinformatic analyses were then conducted on proteomic data obtained from the roots and leaves of the treated material. The aim of this work was to identify, in both chapters, genes/proteins with differential expression in roots and leaves under microgravity conditions, as well as in response to different concentrations of H2O2. To achieve this purpose, in both approaches, the species Sorghum bicolor, Zea mays, and Oryza sativa subs. japonica were used as references. Bioinformatics analysis results revealed unique and specific genes in each of the nine analyzed data libraries, highlighting genes such as C5WVD4 and C5YLK6, associated with isoleucine synthesis and NADPH, respectively, in response to microgravity, and genes with altered expression at different concentrations of H2O2, such as C5XFH6 and B4G143, associated with NADPH supply and photosynthesis in the positive regulation of ROS, respectively. Enriched metabolic pathways in response to microgravity and H2O2, including Selenocompound metabolism, Photosynthesis - antenna proteins, and Pentose phosphate pathway, were also identified. Through this multidisciplinary study, which combines histology, biochemistry, RNA-seq analysis, and proteomics, there is a comprehensive understanding of the effects of microgravity and H2O2 on sugarcane, highlighting changes in tissue structural organization, lignin accumulation, H2O2, and ROS. Therefore, this work assisted in identifying unique and specific genes/proteins expressed in each tissue and the activated metabolic pathways in leaves and roots, elucidating the diverse responses of sugarcane plants under altered gravity conditions with the VSB-30 sounding rocket flight and exposure to different concentrations of H2O2. It reveals a complex network of genes and metabolic pathways that act in response to oxidative stress conditions, triggering defence and tolerance mechanisms. The data obtained advance the understanding of how plants respond to each of the analyzed adverse conditions, employing specific adaptive strategies. Additionally, they emphasize the importance of H2O2 in adaptive and survival responses, as well as the versatility of the abscisic acid (ABA) phytohormone in signaling between roots and leaves. These findings provide valuable insights for the development of genetic improvement strategies and optimized cultivation practices for plant performance under variable conditions.