Memória ao déficit hídrico em folhas e células-guarda de arroz

Abstract

Abiotic stresses are currently one of the main limitations to agricultural production worldwide and the situation has increased dramatically due to climate change. Reductions and poor distribution of precipitation are causing frequent periods of water deficit. Severe droughts have negative impacts on plant growth, physiology and reproduction. Most abiotic stresses are transient and often recurrent. A possible response of plants to a previous stress event is that they can become more responsive to future exposures through the acquisition of memory. This memory process is usually evidenced by an increased response pattern, a more efficient or a faster response. Some molecular mechanisms that support plant memory have been elucidated. The first occurs by the accumulation of signaling metabolites or transcription factors, known as compound / physiological memory, and the second mechanism refers to epigenetic memory. In view of this, the present study focused on unraveling physiological, biochemical, epigenetic and omic mechanisms associated with long-term somatic memory in rice plants and guard cells subjected to different conditions of recurrent drought stress. In the first study, the influence of drought pre-exposure, in two contrasting rice genotypes, on abscisic acid metabolism (ABA) was investigated, quantifying all products of the route as well as the genes encoding the enzymes involved. Thus, we observed that previous stress alters the concentrations of certain products of this metabolism, in both genotypes, related to possible memory responses and to physiological processes. In the second study, physiological and metabolomic changes were investigated in rice plants subjected to recurrent drought and we observed that, at all levels analyzed, the plants show stress memory responses, especially after rehydration. In addition, it was possible to identify possible metabolites that are associated with the memory process. The third and last study demonstrated that the memory of stress can also be observed at the proteomic and epigenetic level in tissue enriched with guard cells of rice, this being the first study demonstrating these results under these conditions. The results of the three studies allowed new insights into the memory mechanisms in rice plants, in addition to a better understanding of the processes involved in drought tolerance.