Comparative analysis of carotenoid accumulation in two goji (Lycium barbarum L. and L. ruthenicumMurr.) fruits

Abstract

BackgroundThe traditional Chinese medicinal plants Lycium barbarum L. and L. ruthenicum Murr. are valued for the abundance of bioactive carotenoids and anthocyanins in their fruits, respectively. However, the cellular and molecular mechanisms contributing to their species-specific bioactive profiles remain poorly understood.ResultsIn this study, the red fruit (RF) of L. barbarum was found to accumulate high levels of carotenoids (primarily zeaxanthin), while they were undetectable in the black fruit (BF) of L. ruthenicum. Cytological and gene transcriptional analyses revealed that the chromoplast differentiation that occurs in the chloroplast during fruit ripening only occurs in RF, indicating that the lack of chromoplast biogenesis in BF leads to no sink for carotenoid storage and the failure to synthesize carotenoids. Similar enzyme activities of phytoene synthase 1 (PSY1), chromoplast-specific lycopene β-cyclase (CYC-B) and β-carotene hydroxylase 2 (CRTR-B2) were observed in both L. ruthenicum and L. barbarum, suggesting that the undetectable carotenoid levels in BF were not due to the inactivation of carotenoid biosynthetic enzymes. The transcript levels of the carotenoid biosynthetic genes, particularly PSY1, phytoene desaturase (PDS), ζ-carotene desaturase (ZDS), CYC-B and CRTR-B2, were greatly increased during RF ripening, indicating increased zeaxanthin biosynthesis. Additionally, carotenoid cleavage dioxygenase 4 (CCD4) was expressed at much higher levels in BF than in RF, suggesting continuous carotenoid degradation in BF.ConclusionsThe failure of the chromoplast development in BF causes low carotenoid biosynthesis levels and continuous carotenoid degradation, which ultimately leads to undetectable carotenoid levels in ripe BF. In contrast, the successful chromoplast biogenesis in RF furnishes the sink necessary for carotenoid storage. Based on this observation, the abundant zeaxanthin accumulation in RF is primarily determined via both the large carotenoid biosynthesis levels and the lack of carotenoid degradation, which are regulated at the transcriptional level.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0269-4) contains supplementary material, which is available to authorized users.

Carotenoid Cleavage Oxygenases from Microbes and Photosynthetic Organisms: Features and Functions

“…It is interesting to note that, due to the intense orange-red color of these C 30 apocarotenoids, the citrus CCD4 activity enhances fruit pigmentation, in contrast to the other CCD4s described so far whose activity is associated with color loss. In other species, such as bitter melon, goji berry, and tomato, the expression of at least one CCD4 gene has been reported in ripened fruits, but no relationship has been established with carotenoid content [148,155,163]. In potato tubers, compared with the yellow ones, CCD4 activity regulates coloration, as indicated by the elevated CCD4 expression in mature white-fleshed tubers [150].…”

LbCML38 and LbRH52, two reference genes derived from RNA-Seq data suitable for assessing gene expression in Lycium barbarum L.

“…used Actin as a reference gene in fruits of two goji cultivars ( Lycium barbarum L. and L. ruthenicum Murr.) for the profiling of genes involved in carotenoid biosynthesis and metabolism13. However, our study demonstrated that LbActin7 exhibited moderately stable expression in some of the treatments in flowers and fruits, but introduced significant errors when normalizing the target gene expression level in leaves and fruits at specific developmental stages (Fig.…”

“…Unlike plants from the same Solanaceae family such as tobacco, tomato, pepper and potato, the whole genome data of Goji are still not available. Previously, Liu and co-workers13 used actin as a reference gene to analyze the expression pattern of genes involved in carotene synthesis in Goji. However, the validity of results is questionable due to the lack of systematic and scientific screening of reference genes.…”

Antioxidants Distribution in Pulp and Seeds of Black and Red Goji Berries as Affected by Boiling Processing

“…Recent research indicates that goji had a lot of biological activities, including antidiabetes [5], antiproliferative activity [4], preserving retinal function [6], and antioxidant activity [7,8]. A lot of research has focused on carotenoids [3] and polysaccharides [4,6]. However, phytochemicals [9,10], such as phenolic compounds [11], including phenolic acids and flavonoids in goji and their antioxidant activity have been less evaluated.…”

“…natively growing in northwest part of China. Goji is a good source of fiber, protein, carotenoids [3], and polysaccharides [4]. Recent research indicates that goji had a lot of biological activities, including antidiabetes [5], antiproliferative activity [4], preserving retinal function [6], and antioxidant activity [7,8].…”