| Abstract
| - The aim of this work was to study the impact of moderately long storage periods at 4 °C upon redorange [Citrus sinensis (L.) Osbeck] anthocyanins production and the expression of structural genesinvolved in their biosynthesis such as phehylalanine ammonia lyase (PAL), chalcone synthase (CHS),dihydroflavonol 4-reductase (DFR), and UDP-glucose flavonoid glucosyl transferase (UFGT). Ourresults showed that low temperature-induced anthocyanins accumulation in red orange juice vesiclesafter 75 days reached values eight times higher than those kept at 25 °C. Furthermore, real-timepolymerase chain reaction showed that expression of PAL, CHS, DFR, and UFGT was stronglyinduced during low temperature exposure since levels of all transcripts increased at least 40-foldwith respect to control samples. Interestingly, in orange fruits subjected to a brief exposure at lowtemperature (45 days) and subsequently kept at 25 °C, the anthocyanins content dropped althoughsamples still maintained higher levels of these pigments than those registered in control oranges.Concordantly, the expression of chs, dfr, and ufgt declined upon return to control conditions, but itwas always much higher in samples subjected to brief cold induction than in the control samples. Onthe contrary, the amount of PAL transcripts became negligible immediately after the temperaturechange from 4 to 25 °C, thus indicating that “early” and “late” genes, respectively, implicated in thefirst and in the last steps leading to the anthocyanins, might be affected by different regulationmechanisms. Keywords: Anthocyanin; red orange; Citrus sinensis; juice vesicles pigmentation; cold temperaturestorage; RT-real time PCR
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