Proteome Dynamics of the Developing Açaí Berry Pericarp (Euterpe oleracea Mart.)

Abstract

Quantitative proteome analysis of four developmental stages of pericarp tissues of the açaí berry (Euterpe oleracea Mart.) was performed by the isobaric labeling of peptides with iTRAQ 4-plex, hydrophilic interaction liquid chromatography pre-fractionation of labeled peptides, and high-performance mass spectrometry analysis. This analysis resulted in the identification of 4286 proteins, of which 476 presented differential abundance between the stages. The differential abundance of these proteins was seen to be coordinated with the metabolic demands during cell division, lignification, and cell expansion at developmental stages 1 and 2 as well as phenolic acid accumulation and metabolic changes in the fruit maturation at developmental stages 3 and 4. The distinct accumulation of anthocyanins observed in the pericarp at developmental stage 4 was correlated with the increase in abundance of some key biosynthetic enzymes, such as leucoanthocyanidin dioxygenase, anthocyanidin O-3-glycosyltransferase, and UDP-glycosyltransferase. Here, evidence is also provided for the presence in the açaí berry of secondary metabolites not previously described in açaí, such as pterostilbene, matairesinol, and furaneol. Together, these results will pave the way for studies aimed at the genetic improvement of the nutritional properties of this important fruit crop.

Phenolic Profile and Antioxidant Properties in Extracts of Developing Açaí (Euterpe oleracea Mart.) Seeds

“…Afterward, the pulp and the seed were carefully separated from each other. 23 Subsequently, the seeds were ground in a knife mill (PULVERISETTE 19, Fritsch, Germany) to a 2 mm particle size and extracted with ethanol/water 1:1 (v/v) in a solid/liquid ratio of 1:8 (m/v) for 60 min at 50 °C under orbital agitation at 120 rpm. The extraction conditions were chosen based on preliminary experiments that evaluated the influence of the solid/ liquid ratio (from 1:5 to 1:15, m/v), extraction time (30 min to 24 h), temperature (30−70 °C), and solvent composition (20−80% ethanol in water).…”

“…A detailed description of each development stage and the criteria for their collection can be found in previous works. 22,23 In the laboratory, the fruits were frozen with liquid nitrogen and freeze-dried. Afterward, the pulp and the seed were carefully separated from each other.…”

“…Açaí fruits in four distinct stages of development (S1, S2, S3, and S4) were collected in natural environmental conditions (without control of temperature, light, humidity, nutrition, or other variables) from a private supplier at the municipality of São Gonçalo do Amarante (03° 33′ 44″ S; 41° 05′ 32″ W), Ceará, Brazil. A detailed description of each development stage and the criteria for their collection can be found in previous works. , In the laboratory, the fruits were frozen with liquid nitrogen and freeze-dried. Afterward, the pulp and the seed were carefully separated from each other .…”

“…Afterward, the preparations were preserved at −80 °C until sectioning, as previously described. 23 The sectioning process used a cryostat (Leica CM1860-UV, Leica Biosystems, Nussloch, Germany) kept at −25 °C, and the embedded seed was attached to the holder with a cryomatrix. The lack of solid endosperm at S1 and S2 stages prevented sectioning of the entire tissue to obtain a representative sample, and the analyses were continued only with S3 and S4, as previously described.…”

Acquiring thin histological sections of açaí (Euterpe oleracea Mart.) seeds for molecular mapping by mass spectrometry imaging

“…However, there is a very small amount of information about the localization of primary compounds in açaí seeds. A previous study has quantitatively analyzed the proteome dynamics and morphological aspects of the açaí pericarp and seed during the developmental stages 17,18 . Also, a recent histochemical study provided the presence of phenolic compounds and carbohydrates in the açaí seed coat and endosperm, respectivelly 19 .…”