Genomics Applied to Iron Stress Tolerance in Rice

Rice is an important cereal worldwide. Outside Asia, Brazil is the largest rice producer, having over 70% of its production as lowland, irrigated rice. Although high yields can be obtained in this system, iron toxicity can occur, causing fields to have losses in production. Iron toxicity is associated with the presence of large concentrations of reduced iron (Fe²⁺) in the soil solution, which occurs in flooded soils and affects rice plants grown under this condition. Symptoms of iron toxicity involve oxidative stress in leaves, as a response to excessive Fe²⁺ absorption by the roots. The responses of plants to stress conditions include stimulus perception, signal transduction and gene transcription activation. Also, LTR (Long Terminal Repeat) retrotransposons can be transcriptionally activated under stress, and drive expression of adjacent genes (e.g. due to alterations to chromatin structure). Our group has been studying genes and LTR retrotransposons that are affected by iron excess, their phylogeny, interactions and level of expression, aiming to understand the physiological basis of the response to this important stress. Novel components and discoveries are discussed.