Application of HPLC–PDA–MS metabolite profiling to investigate the effect of growth temperature and day length on blackcurrant fruit

Summary

Introduction Blackcurrant (Ribes nigrum L.) is an excellent example of a “super fruit” with potential health benefits. Both
genotype and cultivation environment are known to affect the chemical composition of blackcurrant, especially ascorbic
acid and various phenolic compounds. Environmental conditions, like temperature, solar radiation and precipitation can also
have significant impact on fruit chemical composition. The relevance of the study is further accentuated by the predicted
and ongoing changes in global climate.
Objectives The aim of the present study was to provide new knowledge and a deeper understanding of the effects of post
flowering environmental conditions, namely temperature and day length, on fruit quality and chemical composition of
blackcurrant using an untargeted high performance liquid chromatography–photo diode array–mass spectrometry (HPLC–
PDA–MS) metabolomics approach.
Methods A phytotron experiment with cultivation of single-stemmed potted plants of blackcurrant cv. Narve Viking was
conducted using constant temperatures of 12, 18 or 24 °C and three different photoperiods (short day, short day with night
interruption, and natural summer daylight conditions). Plants were also grown under ambient outdoor conditions. Ripe berries were analysed using an untargeted HPLC–PDA–MS metabolomics approach to detect the presence and concentration
of molecules as affected by controlled climatic factors.
Results The untargeted metabolomics dataset contained a total of 7274 deconvolved retention time-m/z pairs across both
electrospray ionisation (ESI) positive and negative polarities, from which 549 metabolites were identified or minimally annotated based upon accurate mass MS. Conventional principal component analysis (PCA) in combination with the Friedman
significance test were applied to first identify which metabolites responded to temperature in a linear fashion. Multi-block
hierarchical PCA in combination with the Friedman significance test was secondly applied to identify metabolites that were
responsive to different day length conditions. Temperature had significant effect on a total of 365 metabolites representing
a diverse range of chemical classes. It was observed that ripening of the blackcurrant berries under ambient conditions,
compared to controlled conditions, resulted in an increased accumulation of 34 annotated metabolites, mainly anthocyanins
and flavonoids. 18 metabolites were found to be regulated differentially under the different daylength conditions. Moreover, based upon the most abundant anthocyanins, a comparison between targeted and untargeted analyses, revealed a close
convergence of the two analytical methods. Therefore, the study not just illustrates the value of non-targeted metabolomics
approaches with respect to the huge diversity and numbers of significantly changed metabolites detected (and which would
be missed by conventional targeted analyses), but also shows the validity of the non-targeted approach with respect to its
precision compared to targeted analyses.
Conclusions Blackcurrant maturation under controlled ambient conditions revealed a number of insightful relationships
between environment and chemical composition of the fruit. A prominent reduction of the most abundant anthocyanins under
the highest temperature treatments indicated that blackcurrant berries in general may accumulate lower total anthocyanins
in years with extreme hot summer conditions. HPLC–PDA–MS metabolomics is an excellent method for broad analysis of
chemical composition of berries rich in phenolic compounds. Moreover, the experiment in controlled phytotron conditions
provided additional knowledge concerning plant interactions with the environment.

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DOI : doi.org/10.1007/s11306-018-146...
NVA : hdl.handle.net/11250/2582286