Memória do estresse em plantas de arroz (BRS-AG) submetidas a estresse recorrente (sal) e cruzado (sal e seca)

Abstract

Abiotic stresses are among the most limiting factors of plant growth and productivity, being salinity and water deficit the main factors responsible for this limitation. Most of these stimuli are transient and, once passed, the plants can recover. However, recovery may not be complete and metabolism may be reorganized. Studies suggest that storing information about a past stress event can benefit plants by preparing them for recurrent or different (crossover) stimuli, a phenomenon associated with the production of memory in plants. 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. The aims of this work was to evaluate the stability of ten reference genes, in order to identify the most suitable for the normalization of transcription in rice plants, cv. BRS AG, submitted to different salt stress conditions, besides the present study focused on the discovery of, molecular, biochemical, omic and physiological mechanisms associated with long-term somatic memory in rice plants submitted to different conditions of recurrent salt stress and cross stress (salt x drought). In the first study, it was demonstrated that in rice plants subjected to different salt stress conditions, the UBC-E2 and GAPDH genes can be used as normalizing genes in leaves, UBQ5 and UBQ10 in sheaths, TIP41 and UBQ10 in rachis and TIP41 and cyclophilin for grains in all conditions tested. On the other hand, the cyclophilin, β-tubulin, EeF1α and ACT11 genes, showed no stability expression, and they are not indicated. In the second study it was observed that rice plants, cv. BRS AG, exposed to recurrent salt stress present different physiological, biochemical, molecular and anatomical responses of plants submitted to salinity for the first time in the grain filling stage, that is, they react differently in terms of the ability to transport and use sucrose in the grains, and the ability to mitigate the effects caused by salt stress. In the third study, we observed that previous stress (salt) alters transcriptional, physiological and hormonal responses to a second drought event in rice plants, related to possible long-term cross-tolerance responses. The fourth and final study demonstrated that the memory of stress and cross-tolerance can also be observed at a metabolic level in rice leaves. The results of the four studies allowed new insights into memory mechanisms and/or cross-tolerance in rice plants, as well as a better understanding of the processes involved in the tolerance to salinity and drought stress.