Abstract
Carotenoids are the principal pigments in the loquat. Although the metabolic pathway of plant carotenoids has been extensively investigated, few studies have been explored the regulatory mechanisms of loquat carotenoids because knowledge of the loquat genome is incomplete. The chromoplast-specific lycopene β-cyclase gene (CYC-B) could catalyze cyclization of lycopene to β-carotene. In this study, the differential accumulation patterns of loquat with different colors were analyzed and virus-induced gene silencing (VIGS) was utilized in order to verify CYC-B gene function. Using a cloning strategy of homologous genes, a CYC-B gene orthologue was successfully identified from the loquat. At a later stage of maturation, CYC-B gene expression and carotenoids concentrations in the ‘Dawuxing’ variety were higher than in ‘Chuannong 1-5-9′, possibly leading to the difference in pulp coloration of loquat. Interference of CYC-B gene expression in the loquat demonstrated clear visual changes. The green color in negative control fruits became yellow, while TRV2-CYC-B silenced fruits remained green. CYC-B gene expression and total carotenoid content in the pulp decreased by 32.5% and 44.1%, respectively. Furthermore, multiple key genes in the carotenoid metabolic pathway synergistically responded to downregulation of CYC-B gene expression. In summary, we provide direct evidences that CYC-B gene is involved in carotenoid accumulation and coloration in the loquat.
Highlights
Loquat (Eriobotrya japonica Lindl) is a member of the Rosaceae family and is native to the southeast of China [1]
CYC-B and capsanthin-capsorubin synthase (CCS) proteins from Citrus were highly homologous. These results indicated that the isolated gene from the loquat belonged to the chromoplast-specific lycopene β-cyclase (CYC-B)
The results indicated that the carotenoid accumulation in loquat pulp and interfered loquat coloration
Summary
Loquat (Eriobotrya japonica Lindl) is a member of the Rosaceae family and is native to the southeast of China [1]. Carotenoids are the principal pigments in loquat and their concentration has been shown to be significantly correlated with fruit coloration [2,3,4]. Few studies of the regulatory mechanism of loquat carotenoids have been published due to the lack of information about its genome. With the development of modern molecular biological techniques, an investigation of the genetic mechanisms that regulate the accumulation of carotenoids in the loquat is timely. Plant carotenoids are C40 isoprenoids with polyene chains that may contain up to 15 conjugated double bonds. They are important components of photosynthetic organisms due to their chemical properties [7]
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