Triacylglycerol Composition of Developing Ribes nigrum and Ribes rubrum Seeds and the Related Gene Expression Levels
Anssi L. Vuorinena, Marika Kalpioa, Kaisa M. Linderborga, Kati B. Hoppulab, Saila Karhuc, Baoru Yanga, Heikki Kallioa, 
aFood Chemistry and Food Development, Department of Biochemistry, University of Turku, Turku, Finland
b MTT Agrifood Research Centre Finland, Sotkamo Research Station, Sotkamo, Finland
c MTT Agrifood Research Centre Finland, Plant Production Research Horticulture, Piikkiö, Finland

Black currant (Ribes nigrum L.) and red currant (Ribes rubrum L.) are important berry crops widely grown in Central and Northern Europe. Their seed oil contains large amounts of polyunsaturated fatty acids, including stearidonic acid (18:4n–3) and γ-linolenic acid (18:3n–6). There is evidence suggesting positive effects of the seed oil on atopic dermatitis.
The aim of this work was to study the biosynthesis of triacylglycerols (TAG) in developing seeds of each species. We targeted the problem by studying the expression of genes encoding enzymes in the TAG synthesis pathway in a time series collected during two years from two replicate experiments grown in two locations within Finland (south: 60° N and north: 66° N). A total of six common cultivars were included. The study was conducted using quantitative PCR for the genes of interest. 
Our results show the expression levels of different enzyme genes at 1, 2, 3, 4, and 5 weeks after flowering. The expression of several genes changed significantly during the growing season. The most notable increases during seed development were detected in the expression of the genes for Δ6-desaturase and phospholipid:diacylglycerol acyltransferase (PDAT) in both of the studied Ribes species. Other highly increased expressions included fatty acid desaturases 2 and 3. These results were complemented with analysis of fatty acid and TAG composition at the same time points using gas chromatography (GC) and high performance liquid chromatography (HPLC). Growth location had little effect on the seed oil composition or the related gene expression levels, but there were significant differences between species.
Corresponding author: Anssi L. Vuorinen (anssi.vuorinen@utu.fi)