Memória epigenética, transcricional e fisiológica em plantas de arroz submetidas ao estresse salino

Abstract

Rice is cultivated in several environments, however, abiotic stresses, such as salinity, critically threaten its production, causing significant yield losses. In addition, the environment around the plant is constantly changing, not only throughout the seasons and years, as we currently observe the effects of global warming, but also every day. Most abiotic stress is transient and often recurrent. One possible response of plants to a first stress event is that they become more resistant to future exposures through memory acquisition. Generally, this memory process is evidenced by an increased response pattern, a more efficient response or a faster response. Some molecular mechanisms that support the plants memory have already been elucidated. The first is the accumulation of signaling metabolites or transcription factors, known as physiological / molecular memory, and the second mechanism refers to epigenetic memory. In addition to these two mechanisms, dramatic changes in gene expression patterns may occur, illustrating the concept of 'transcriptional memory' and revealing the existence of 'memory genes'. Studies relating the memory process and saline stress are rare, especially in rice plants. Thus, the present study focused on the discovery of physiological, biochemical, molecular and epigenetic mechanisms associated with long-term somatic memory in rice plants submitted to different salt stress conditions. Additionally a study was conducted to characterize modules of co-expressed genes in response to salinity. In the first study, it was demonstrated that rice plants submitted to a recurrent stress presented distinct patterns of expression of plants that submitted to only one event, evidencing a transcriptional memory. In the second study differences in the memory process were observed in contrasting genotypes, and it was possible to observe which physiological, biochemical and epigenetic variables contributed to this distinction. The third and last study demonstrated, through of a co-expression network, the main modules of coexpressed genes that are altered in rice plants submitted to saline stress, and characterized them functionally. The results of the three studies allowed new insights into memory mechanisms in rice plants, as well as a better understanding of the processes involved in the tolerance to salinity stress.