A coordinate expression of structural genes determine the production of phenolic acids and flavonoids in tubers from Andean potato varieties

VALIÑAS, M; LANTERI ML; ARJEN TEN HAVE; ANDREU AB

Mar del Plata

Congreso; XV Congreso Latinoamericano de Fisiología Vegetal; 2014

P { margin-bottom: 0.21cm; } Two major groups of secondary metabolites are synthesized from p-coumaroyl CoA, namely, phenolic acids and flavonoids. Chlorogenic acid (CGA) is the major phenolic acid antioxidant in potato tubers. The flavonoids, in order of abundance, were reported to be catechin, epicatechin, erodictyol, kaempeferol and naringenin. Anthocyanins are a sub-group within the flavonoids and present in substantial amounts in pigmented flesh potatoes. A number of biosynthetic routes, involving two enzymes which belong to acyltransferase gene family (HQT and HCT) lead to CGA production. The synthesis of anthocyanins requires several consecutive steps, catalyzed by CHS, CHI, F3H, DFR, ANS and 3UGT. Two branching points that imply reductase activity, LCR andANR, result in the production of (+)catechin and (-)epicatechin, respectively. Natural variation in the potato germplasm offer nutritionally interesting potato genotypes. The very diverse native Andean potato landraces have been shown to have more genetic diversity as compared to modern potato varieties and, so far, are largely unexplored from a nutritional point of view. Promising routes for enhancing the quality of staple crops include biotechnologies and conventional plant breeding. However, before starting labor-intensive plant breeding programs, a profound knowledge of how the metabolic network works is required. Thus, a comparative analysis between skin and flesh of potato tubers from four Andean varieties was performed. To achieve this, the expression levels of the structural genes together with the metabolite levels were quantified by RT-qPCR and HPLC-DAD, respectively. Results show that both metabolites and transcripts levels of genes responsible for phenolic acids and flavonoids biosynthesis were, in general, higher in skin than in flesh. CGA levels were well correlated with HCT rather than HQT. Despite the fact that catechin and epicatechin were present we could not detect LCR transcript while ANR does not show a clear pattern between tissues. Therefore the synthesis of flavan-3-ols would imply an ANR with epimerase activity. There was a good correspondence between transcript levels of CHS, CHI, F3H, DFR and ANS and with the anthocyanin content. Together these data support the hypothesis that the synthesis of phenolic acids and flavonoids is regulated at transcriptional level in a coordinate manner.