Respostas morfofisiológicas, metabolômicas e transcritômicas da palma de óleo (Elaeis guineensis) aos estresses abióticos de seca e salinidade

Abstract

Oil palm (Elaeis guineensis) is a monocotyledonous plant species of great economic importance worldwide. It is the oilseed with the highest oil productivity. For this reason, it has been considered a key piece for diversifying the sources of vegetable oil in Brazil. In this country, its cultivation has expanded in to regions subjected to long and severe dry season. Consequently, irrigation bas been necessary. Two abiotic stresses may result, namely, drought and salinity. Seeking to anticipate them, this work aimed at a multidisciplinary study to evaluate the morphophysiological, metabolomic and transcriptomic responses of oil palm under drought and salinity stress. For this, oil palm plants were submitted to saline (0; 0.5; 1.0; 1.5 and 2.0 g NaCl / 100 g substrate) or drought (water withhold) stresses. Then, they were evaluated by different tools : a) Phenomics: strict water control and daily monitoring of water levels, gas exchange analysis, chlorophyll concentration and chlorophyll fluorescence parameters, leaf temperature, biomass, mineral nutrition, among others; (b) Metabolomics: metabolic profile analysis; and (c) Transcritomics: analysis of differential expression, functional annotation and gene ontology. The salinity bioassay was efficient, since the physiological parameters evaluated were able to distinguish the different levels of NaCl. The higher the dose of salt and the time of exposure, the greater the physiological damage to the plants. It was possible to identify the difference among the groups of metabolites / transcripts of the plants under different salt concentrations, corroborating the physiological data. The drought bioassay also proved to be efficient, because the longer the period of stress, the lower the water levels in the substrate, and the greater the physiological damage to plants. Under drought, groups of differentially expressed genes and metabolites were identified. For both stresses, the main physiological damages, such as reduced photosynthetic rates, chlorophyll concentration index and photochemical activity, are related to reduced water absorption and lower water content in the tissues. This was reflected in the increase in leaf temperature and reduction of plant fresh weight. In response to stresses, plants alter their metabolism and produce different transcripts and metabolites, which explains the differences found between controls and stressed. Further studies will be necessary to verify if there is a correspondence between the transcripts and metabolites found under different levels of stress, as well as their relationship with the physiological changes. The present work represents a consolidated base and the beginning of an extensive range of possible multidisciplinary correlations that will be explored within and between the different types and levels of stress studied.