Gamma-linolenic Acid from Fifty-seven Ribes Species and Cultivars

γ-linolenic acid (GLA, 18:3n-6) is a bioactive fatty acid (FA) that exerts several healthy actions; however, its occurrence is restricted to a few oils. The goal of this study was to detect GLA-rich Ribes species and cultivars (cv), and to achieve this the seeds of 7 Ribes taxa and 50 Ribes cv were surveyed for FA profiles. The highest GLA percentages were found in R. nigrum cv 'Plotnokistnaya', 'Volshebnica', 'Atlant' and 'Nara' (22.6, 22.1, 20.9, and 20.0% of total FA, respectively) and also in R. komarovii (19.6%) and R. nigrum var. sibiricum (18.3%). Stearidonic acid (SDA, 18:4n-3) had the highest values in both R. rubrum 'Konstantinovskaya' and R. niveum 'Smolyaninovskaya' (4.8%). GLA content ranged from 0.4 in some R. rubrum cv and R. niveum 'Smolyaninovskaya' to 3.5 g/100 g seeds in R. nigrum 'Plotnokistnaya'. Principal component analysis (PCA) was performed using PUFA profiles, which allowed grouping Ribes sections as well as black currant cv derived from different pedigree within the section Coreosma. All taxa and cv checked here are valuable by-product sources, given the high GLA percentages contained in their seed oils. Such cv could be used for healthy oils production, as well as for breeding to obtain new cv with improved GLA concentrations.

Isolation and Analysis of Anthocyanin Pathway Genes from Ribes Genus Reveals MYB Gene with Potent Anthocyanin-Inducing Capabilities

Horticultural crops of the Ribes genus are valued for their anthocyanin-rich fruits, but until now, there were no data about the genes and regulation of their flavonoid pathway. In this study, the coding sequences of flavonoid pathway enzymes and their putative regulators MYB10, bHLH3 and WD40 were isolated, and their expression analyzed in fruits with varying anthocyanin levels from different cultivars of four species belonging to the Ribes genus. Transcription levels of anthocyanin synthesis enzymes and the regulatory gene RrMYB10 correlated with fruit coloration and anthocyanin quantities of different Ribes cultivars. Regulatory genes were tested for the ability to modulate anthocyanin biosynthesis during transient expression in the leaves of two Nicotiana species and to activate Prunus avium promoters of late anthocyanin biosynthesis genes in N. tabacum. Functional tests showed a strong capability of RrMyb10 to induce anthocyanin synthesis in a heterologous system, even without the concurrent expression of any heterologous bHLH, whereas RrbHLH3 enhanced MYB-induced anthocyanin synthesis. Data obtained in this work facilitate further analysis of the anthocyanin synthesis pathway in key Ribes species, and potent anthocyanin inducer RrMyb10 can be used to manipulate anthocyanin expression in heterologous systems.

Triacylglycerol biosynthesis in developing Ribes nigrum and Ribes rubrum seeds from gene expression to oil composition

Oils with sufficient contents of fatty acids, which can be metabolized into precursors of anti-inflammatory eicosanoids, have potential health effects. Ribes sp. seed oil is rich in α-linolenic, γ-linolenic and stearidonic acids belonging to this fatty acid group. Only a few previous studies exist on Ribes sp. gene expression. We followed the seed oil biosynthesis of four Ribes nigrum and two Ribes rubrum cultivars at different developmental stages over 2 years in Southern and Northern Finland with a 686 km latitudinal difference. The species and the developmental stage were the most important factors causing differences in gene expression levels and oil composition. Differences between cultivars were detected in some cases, but year and location had only small effects. However, expression of the gene encoding Δ(9)-desaturase in R. nigrum was affected by location. Triacylglycerol biosynthesis in Ribes sp. was distinctly buffered and typically followed a certain path, regardless of growth environment.

Flavonol Glycosides in Currant Leaves and Variation with Growth Season, Growth Location, and Leaf Position

Flavonol glycosides (FG) were analyzed in the leaves of six currant cultivars (Ribes spp.) with HPLC-DAD, HPLC-MS/MS, and NMR. The average amounts of the 12 major, identified FG constituted 86-93% (9.6-14.1 mg/g DW) of the total of 27 FG found. Quercetin and kaempferol were the major aglycones with trace amounts of myricetin. Quercetin-3-O-(2,6-α-dirhamnopyranosyl-β-glucopyranoside), quercetin-3-O-(2-β-xylopyranosyl-6-α-rhamnopyranosyl-β-glucopyranoside), and kaempferol-3-O-(3,6-α-dirhamnopyranosyl-β-glucopyranoside) were identified for the first time in currant leaves and existed in a white currant cultivar 'White Dutch' only. Kaempferol-3-O-β-(6'-malonyl)glucopyranoside was also a new compound existing in abundance in five cultivars but not in the white one. The results show the primary importance of the genetic background of the cultivars. The content of malonylated FG of special importance in cardiovascular health decreased regularly during summer. Time of collection and leaf position were more prominent factors affecting the composition than were the year of harvest or the growth latitude. Randomly collected leaves differed in their FG profiles from those collected from the middle position of new branches.