Characterization of dicaffeoylspermidine derivatives related glucosyltransferases during fruit development of goji berry

The fruit of Lycium barbarum (Lb), known as red goji berry, is a "superfruit" due to its abundance of bioactive compounds. Among these compounds, dicaffeoylspermidine derivatives (DCSPDs) have anti-oxidant and anti-Alzheimer's Disease activity. This study employed ultra-high-performance liquid chromatography with tandem mass spectrometry to investigate metabolic changes during the development and ripening stages of red goji berries. Totally 97 compounds, including 51 DCSPDs, were tentatively identified. Correlation analysis of these DCSPDs revealed that glycosyltransferases (GTs) play an important role in the formation of glycosylated DCSPDs. In vitro experiments characterized 3 novel GTs could add a glucosyl moiety to N1-caffeoyl-N10-dihydrocaffeoyl spermidine. Homologous GTs from L. ruthenicum (Lr) exhibited similar activity, despite the absence of abundant glycosylated DCSPDs in Lr. These findings provide insights into the metabolic changes and interconnections among active compounds in red goji berries. The identified GTs hold potential for metabolic engineering of DCSPDs and functional food development.

Identification and expression analysis of the WRKY gene family during different developmental stages in Lycium ruthenicum Murr. fruit

Background

The WRKY gene family, one of the major transcription factor families in plants, plays crucial regulatory roles in physiological and biological developmental processes, and the adaptation of plants to the environment. However, the systematic study of WRKY structure, expression profiling, and regulatory functions has not been extensively reported in Lycium ruthenicum, although these aspects have been comprehensively studied in most plant species.

Methods

In this study, the WRKY genes were identified from a L. ruthenicum transcriptome database by using bioinformatics. The identification, phylogenetic analysis, zinc-finger structures, and conserved motif prediction were extensively explored. Moreover, the expression levels of 23 selected genes with fragments per kilobase of exons per million mapped reads (FPKM) >5 were assayed during different fruit developmental stages with real-time quantitative polymerase chain reaction (RT-qPCR).

Results

A total of 73 putative WRKY proteins in the L. ruthenicum transcriptome database were identified and examined. Forty-four proteins with the WRKY domain were identified and divided into three major groups with several subgroups, in accordance with those in other plant species. All 44 LrWRKY proteins contained one or two conserved WRKY domains and a zinc-finger structure. Conserved motif prediction revealed conservation of the WRKY DNA-binding domain in L. ruthenicum proteins. The selected LrWRKY genes exhibited discrete expression patterns during different fruit developmental stages. Interestingly, five LrWRKYs (-20, -21, -28, -30, and -31) were expressed remarkably throughout the fruit developmental stages.

Discussion

Our results reveal the characteristics of the LrWRKY gene family, thus laying a foundation for further functional analysis of the WRKY family in L. ruthenicum.

An integrated approach for harvesting Natal plum (Carissa macrocarpa) for quality and functional compounds related to maturity stages

This study aims to link morphological and physico-chemical parameters with maturity stages of Natal plum (Carissa macrocarpa), an edible southern African fruit. Harvesting via an integrative holistic approach is recommended for optimal quality and functional compounds. Fruits at dark green (M1), light green (M2), colour break or pink (M3), red (M4), dark red (M5) stages were harvested in 2016 and 2017 seasons. The principal component analysis illustrated the colour value a* (redness), fruit weight, size (length and width), sugars (glucose and fructose), ascorbic acid content, cyanidin derivatives (cyanidin-3-O-pyranoside, cyanidin 3-O-β-sambubioside, cyanidin-3-O-glucoside), naringenin 4'-O-glucoside, and antioxidant property (FRAP) were higher in the following order of maturity stages M5 > M4 > M3 > M2 > M1. Quercetin 3-O-rhamnosyl galactoside and glucoside were higher in green (h° higher) firm M1 to M3 stages. A strong correlation exists between fruit weight, size, a* value and cyanidin derivatives or naringenin 4'-O-glucoside or ascorbic acid content or antioxidant activity. Thus, the M4 and M5 stages of Natal plum can serve as functional food.

Expression of hydroxytyrosol and oleuropein biosynthetic genes are correlated with metabolite accumulation during fruit development in olive, Olea europaea, cv. Koroneiki

Olive tree is one of the most valuable crops cultivated for its oil that is rich in antioxidants. The beneficial effects of oleuropein and hydroxytyrosol (HT), the most abundant and the most powerful antioxidant respectively, as well as tyrosol, HT's precursor molecule, are well studied however their biosynthetic pathways are not yet clarified. The transcriptome analysis of the young olive fruit, cultivar "Koroneiki", revealed transcripts of all the enzymes used to reconstitute the biosynthetic pathway of tyrosol and HT in other organisms. We also identified transcripts of the genes that encode for enzymes involved in the secologanin biosynthesis, oleuropein's precursor molecule. Following the transcriptome analysis, the relative expression of the transcripts was monitored during fruit development and compared to the concentration of the 3 metabolites they synthesize at the same developmental stages. The highest expression levels, accompanied by the maximum concentration of the three metabolites, was found in the young olive fruit. The correlation between the expression profile and the metabolites' concentration indicates that the transcripts were correctly identified and the synthesis of the compounds is regulated at a transcriptional level. Interestingly, HT showed a sudden increment in the final developmental stage of the black mature fruit that is attributed to oleuropein catabolism.