Gene expression analysis of enzymes of the carotenoid biosynthesis pathway involved in β-cryptoxanthin accumulation in wild raspberry, Rubus palmatus

beta-cryptoxanthin (beta-Cry), a xanthophyll, is unlike other abundant carotenoids, such as alpha-carotene, beta-carotene, lycopene, lutein, and zeaxanthin. It is not found in most fruits or vegetables but is found only in specific fruits, such as hot chili pepper, persimmon, and citrus fruits. Because recent reports suggest that beta-Cry intake is beneficial to human health, the xanthophyll requires further investigation. Although beta-Cry accumulates in the fruit of wild raspberry, Rubus palmatus, it is not present in cultivated raspberry. In the present study, two wild raspberry species were studied-R. palmatus, which accumulates beta-Cry in the fruit, and R. crataegifolius, which does not accumulate beta-Cry. Four carotenoid biosynthetic enzymes derived from these two species were analyzed phytoene synthase (PSY), lycopene beta-cyclase (LCYb), beta carotene hydroxylase (HYb), and zeaxanthin epoxidase (ZEP). Expression levels of their genes were also assessed to elucidate mechanism underlying beta-Cry accumulation. Partial gene sequences of RubPSY, RubLCYb, RubHYb, and RubZEP, isolated from immature raspberry fruits of R. palmatus, were used as probes for Northern blot analysis. RubZEP expression ceased as the fruits matured, possibly because of reduced production of zeaxanthin. beta-Cry is considered to be an intermediate compound that accumulates in the mature fruits of R. palmatus. High expression of RubPSY was detectable in the mature fruits of R. crataegifolius, and the expression of RubLCYb, RubHYb, and RubZEP was detectable during all stages of fruit maturation. In contrast, beta-Cry was absent in the mature fruits of R. crataegifolius. (C) 2017 Elsevier Inc. All rights reserved.