Lucas do Espirito Santo Gomes¹, Talles de Oliveira Santos¹, Vitor Batista Pinto ¹

Sugarcane is one of Brazil’s major crops, with strategic importance for both the national economy and energy transition. Its expansion into acidic, low-fertility soils exposes the crop to aluminum (Al) toxicity, especially in the Al³⁺ form, which is highly bioavailable and phytotoxic. This ion interferes with essential processes such as cell division, photosynthesis, respiration, and nutrient uptake, ultimately impairing root growth and crop productivity. In this study, two sugarcane genotypes (RB867515 and RB966928), provided by RIDESA/UFRRJ, were evaluated for their physiological and proteomic responses to Al stress. After 30 days of growth in Basaplant® substrate, uniform plants were transferred to a hydroponic system and exposed to 221 µmol Al³⁺ (AlCl₃) at pH 4.5 for 10 days. Physiological analyses revealed distinct responses between genotypes. In RB966928, a reduction in chlorophyll content and an increase in the Nitrogen Balance Index (NBI) were observed, suggesting impacts on photosynthesis and nitrogen metabolism. RB867515, in contrast, maintained chlorophyll levels and exhibited increased accumulation of flavonoids and anthocyanins compounds associated with antioxidant defense and mitigation of oxidative stress caused by Al. Shotgun proteomic analysis identified 776 proteins, with 37 differentially accumulated in RB966928 (treatment vs. control), 39 in RB867515, and 128 in the genotype comparison under stress. In RB966928, enriched biological processes included malate and dicarboxylic acid metabolism and translation factors. Malate exudation is known to reduce Al toxicity through chelation and also contributes to phosphorus and nitrogen acquisition. In RB867515, notable proteins included phenylalanine ammonia-lyase and carbonic anhydrase, both upregulated under Al treatment. Phenylalanine metabolism is linked to the biosynthesis of flavonoids, supporting the observed physiological data. Carbonic anhydrase, a metalloenzyme involved in photosynthesis and CO₂ metabolism, is widely reported to be responsive to abiotic stress and contributes to maintaining cellular homeostasis. Protein–protein interaction analysis (RB867515 vs. RB966928 under Al) revealed KEGG pathway enrichment for the tricarboxylic acid (TCA) cycle, glutathione metabolism, and starch and sucrose biosynthesis. Among the upregulated proteins, sucrose synthase was highlighted, a key enzyme in carbon metabolism previously linked to Al stress response in maize roots. Its accumulation in sugarcane leaves suggests a possible role in carbon allocation under stress conditions. Together, the integration of physiological and proteomic data reveals distinct response mechanisms to Al among the genotypes, highlighting pathways related to antioxidant defense, energy metabolism, and reprogramming of carbohydrate metabolism.

Agradecimentos: This research was supported by National Council for Scientific and Technological Development (CNPq), the Foundation for Research Support of Rio de Janeiro State (FAPERJ), the Brazilian Federal Agency for Support and Evaluation of Graduate Education (Capes), and the Inter-University Network for the Development of Sugarcane and Energy (RIDESA)